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1969 Ultraviolet Emission and Absorption Spectra Produced by Organic Compoundsin Oxyhydrogen Flames. Vega Jean ott mithS Louisiana State University and Agricultural & Mechanical College
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Recommended Citation Smith, Vega Jean ott, "Ultraviolet Emission and Absorption Spectra Produced by Organic Compoundsin Oxyhydrogen Flames." (1969). LSU Historical Dissertations and Theses. 1692. https://digitalcommons.lsu.edu/gradschool_disstheses/1692
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SMITH, Vega Jean Ott, 1937- ULTRAVIOLET EMISSION AND ABSORPTION SPECTRA PRODUCED BY ORGANIC COMPOUNDS IN OXYHYDROGEN FLAMES,
The Louisiana State University and Agricultural and Mechanical College, Ph.D., 1969 Chemistry, analytical
University Microfilms, Inc., Ann Arbor, Michigan ULTRAVIOLET EMISSION AND ABSORPTION SPECTRA PRODUCED BY ORGANIC COMPOUNDS IN OXYHYDROGEN FLAMES
A Dissertation
Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy
in
The Department of Chemistry
by Vega Jean Smith B.S.j University of Alabama, 1959 August, I9 6 9 ACKNOWLEDGEMENTS
The writer would like to take this opportunity to express thanks
to Professor James W. Robinson for the direction of this research.
In addition she would like to express sincere appreciation to
the faculty and staff of the Chemistry Department at Louisiana State
University for their teaching, encouragement, and assistance. Of
the technical staff in particular she would like to thank Mr. J. R.
Hoffman, Mr. G. H. Sexton, and Mr. E. T. Keel.
The loan of an Atomic Absorption Instrument by Beckman Instru
ments, Inc. is gratefully acknowledged. "Thus it will be found that, in general,
Salts of soda give a copious and purely homo
geneous yellow.
Salts of potash give a beautiful pale violet...
Salts of strontia give a magnificent crimson. If
analyzed by the prism two definite yellows
are seen, one of which verges strongly to
orange...
Salts of copper give a superb green, or blue green.
Salts of iron (protoxide) give white, where the
sulphate was used...
The colours thus communicated by the different
bases to flames, afford in many cases a
ready and neat way of detecting extremely
minute quantities of them;..."
Herschel, J.F.W., Encyclopedia Metropolitana. p. kjQ, J.J. Griffen, London, 18^8.
iii TABLE OF CONTENTS
Page
INTRODUCTION...... 1
A. GENERAL REVIEW OF FLAMES AND FLAME PROCESSES...... 1
1. General Background...... 1
2. Flame Spectroscopy...... 1
3. Some Energy Aspects of Flames...... 3
k. Chemical Reactions in Flames...... 6
B. GENERAL REVIEW OF THE USE OF FLAMES IN CHEMICAL
ANALYS IS...... 8
1. Flame Photometry...... 8
2. Atomic Absorption...... 11
3. Atomic Fluorescence...... 17
k. The Determination of Nonmetals byFlame
Photometry and Atomic Absorption...... I9
5. The Use of Organic Solvents in Flame Photome
try, Atomic Absorption, and Atomic Fluores
cence...... 21
6. Reducing Flames and Chemiluminescence...... 23
C. PURPOSE OF THE INVESTIGATION REPORTED IN THIS THESIS. 2k
DESCRIPTION OF EXPERIMENTAL CONDITIONS...... 26
A. DESCRIPTION OF THE EQUIPMENT...... 26
B. ORGANIC COMPOUNDS STUDIED...... 28
C. PROCEDURE...... 29
iv TABLE OF CONTENTS (Cont'd)
Page
RESULTS AND DISCUSSION...... 31
A. EMISSION SPECTRA...... 31
1. Wavelengths of Band Maxima and Identification
of the Species Emitting......
2. Comparisons of Emission Spectra Produced by
Different Solvents...... 46
3. Emission Profiles for Fragments...... J2
4. Sensitivity Estimates for Emission Bands Pro
duced by Excited NH and CH Fragments...... 79
5 . Effects of Varying the Hydrogen to Oxygen Ratio
in the Flame on the Emission Spectra...... 79
6. Effects of Aspirating with Hydrogen instead of
Oxygen on the Emission Spectra...... 8 7
B. ABSORPTION SPECTRA...... 8 8
1. Wavelengths of Band Maxima and Identification
of the Species Absorbing...... 8 8
2. Comparisons of Absorption Spectra Produced
by Different Solvents...... 102
3. Absorption Profiles for Fragments...... 140
4. Absorption of Atomic Lines by Flames and by
Organic Solvents...... 146
SUMMARY...... 169
REFERENCES...... I7I
v LIST OF TABLES
TABLE PAGE
I. Emission Bands Produced by the Oxyhydrogen Flame...... 31
II. Emission Bands Produced when Hydrocarbon Compounds or Organic Compounds Containing Oxygen were Sprayed into the Flame...... 33
III, Emission Bands Produced when Compounds Containing Nitrogen were Sprayed into the Flame...... 36
IV. Emission Bands Produced when Compounds Containing Phosphorus were Sprayed into the Flame...... 37
V. Emission Bands Produced when Organic Compounds Con taining Sulfur were Sprayed into the Flame...... 38
VI. Emission Bands Produced by Oxyhydrogen Flames into which Organic Compounds were Sprayed...... 4U
VII. Solvent Aspiration Rates...... A 7
VIII. Absorption Bands Produced by the Oxyhydrogen Flame jk
IX. Absorption Bands Produced when Hydrocarbon Compounds or Organic Compounds Containing Oxygen were Sprayed into the Flame...... 9 8
X. Absorption Bands Produced when Compounds Containing Nitrogen were Sprayed into the Flame...... 97
XI. Absorption Bands Produced when Compounds Containing Phosphorus were Sprayed into the Flame...... 100
XII. Absorption Ba.nds Produced when Organic Compounds Containing Sulfur were Sprayed into the Flame...... 102
XIII. . Absorption Bands Produced by Oxyhydrogen Flames into which Organic Compounds were Sprayed...... 103
XIV. Absorption of Atomic Resonance Lines by Oxyhydrogen Flames into which Organic Solvents were Sprayed...... I55
XV. Emission Signals from Unmodulated Flames...... ,..,..... 160
XVI. Absorption of Atomic Resonance Lines by Solvent Sprays...... 161 LIST OF FIGURES
FIGURES PAGE
1. Flame Emission Spectrum Produced by Manganese Superimposed on the Background Emission from the Oxyacetylene Flame...... 12
2. Diagram of the Equipment Used...... 27
3. Emission Produced by Excited Water Molecules in the Oxyhydrogen F lame ..... 3^-
U. Emission Bands Produced by Excited CH and C2 Fragments... 35
5. Emission Bands Produced by Excited CN and NO Fragments... k-0
6 . Emission Bands Produced by Excited PO Fragments...... ^1
7. Emission Bands Produced by Excited PO Fragments...... k-2
8. Emission Bands Produced by Excited CS Fragments...... k-J
9- Emission Produced by Excited CC1 Fragments...... 4 3
10-a. Emission Spectrum of the Oxyhydrogen Flame at a Height of 0.75 cm...... 50
10-b. Flame Emission Spectrum of Benzene at a Height of O .7 5 cm...... 51
10-c. Flame Emission Spectrum of Butyl Alcohol at a Height of 0.75 cm...... 52
10-d. Flame Emission Spectrum of Pyridine at a Height of 0 .7 5 cm...... 53
10-e. Flame Emission Spectrum of Tributyl Phosphate at a Height of 0.75 cm......
10-f. Flame Emission Spectrum of Thiophene at a Height of 0 .7 5 cm...... 55
11-a.. Emission Spectrum of the Oxyhydrogen Flame at a. Height of 2 cm...... 56
11-b. Flame Emission Spectrum of Benzene at a Height of 2 cm...... 57
11-c. Flame Emission Spectrum of Butyl Alcohol at a Height of 2 cm...... 58
vii FIGURES PAGE
11-d. Flame Emission Spectrum of Pyridine at a Height of 2 cm ,...... 59
U-e. Flame Emission Spectrum of Tributyl Phosphate a t a. Height of 2 cm...... 60
11-f. Flame Emission Spectrum of Thiophene at a Height of 2 cm...... 61
12-a. Emission Spectrum of the Oxyhydrogen Flame at a Height of 3 cm...... 62
12-b. Flame Emission Spectrum of Benzene at a Height of 3 cm...... 6 3
12-c. Flame Emission Spectrum of Butyl Alcohol at a Height of 3 cm...... 6A
12-d. Flame Emission Spectrum of Pyridine at a Height of 3 cm...... 65
12-e. Flame Emission Spectrum of Tributyl Phosphate at a Height of 3 cm...... 66
12-f. Flame Emission Spectrum of Thiophene at a Height of 3 cm...... 6 7
I3~a. Flame Emission Spectrum of Pyridine...... 68
13-b. Flame Emission Spectrum of Nitroethane...... 69
16-a. Flame Emission Spectrum of Chloroform...... 70 lJl-b. Flame Emission Spectrum of Butyl Chloride...... 71
15. Flame Emission Profile at 309..nm...... 7^
16. Flame Emission Profile at i+3l nm...... 7^
17- Flame Emission Profile at A68 nm ...... 75
18. Flame Emission Profile at 3 8 6 nm...... 75
19. Flame Emission Profile at 356 nm...... 76
20. Flame Emission Profile at 2^-6..nm...... 76
21. Flame Emission Profile at 327..nm...... 77
viii FIGURES PAGE
22. Flame Emission Profile at 259 nm...... * 77
23. Flame Emission Profile at 3 2 8 nm...... 78
2 h . Flame Emission Profile at 2 5 8 nm...... 78
25-a. Emission Spectrum of the Oxyhydrogen Flame at a Hydrogen to Oxygen Ratio of 5/3*5 and a Height of 0.75 cm...... 8l
2 5-b. Emission Spectrum of the Oxyhydrogen Flame at a Hydrogen to Oxygen Ratio of 5/3*5 and a Height of 2..cm...... 82
25-c. Emission Spectrum of the Oxyhydrogen Flame at a Hydrogen to Oxygen-Ratio of 5/3*5 an^ a Height of 3..cm...... 83
2o-a. Flame Emission Spectrum of Benzene at a Hydrogen to Oxygen Ratio of 5/3*5 and a. Height of 0.75 cm...... 8^
26-b. Flame Emission Spectrum of Benzene at a Hydrogen to Oxygen Ratio of 5/3*5 and a Height of 2 cm...... 85
26-c. Flame Emission Spectrum of Benzene at a Hydrogen to Oxygen Ratio of 5/3*5 anc^ a Height of 3 cm...... 86
27”a. Flame Emission Spectrum of Pyridine at a Height of 0.75 cm with Hydrogen Aspiration...... 89
27_b. Flame Emission Spectrum of Pyridine at a. Height of 2 cm with Hydrogen Aspiration, ...... 90
27“c. Flame Emission Spectrum of Pyridine at a Height of 3 cm with Hydrogen Aspiration...... $)1
28. Flame Absorption Spectrum of Pyridine with Source Beam Diameter 0.7 cm...... 93
29. Absorption Bands Produced by CH and Q2 Fragments...... 95
30. Absorption Bands Produced by NH and CN Fragments...... 9 8
31. Absorption Bands Produced by CN Fragments...... 99
32. Absorption Bands Produced by PO Fragments...... 101
33-a. Hydrogen Lamp...... 108
33-b. Absorption Spectrum of the Oxyhydrogen Flame at a Height of 0.75 cm...... 109 FIGURE PAGE
33-c. Flame Absorption Spectrum of Benzene at a Height of 0.75 cm...... 110
33-d. Flame Absorption Spectrum of Pyridine at a Height of 0.75 cm...... Ill
33-e. Absorption Spectrum of Pyridine at a. Height of 0.75 cm...... 112
33-f. Flame Absorption Spectrum of Tributyl Phosphate at a Height of 0.75 cm...... 113
33-g. Flame Absorption Spectrum of Thiophene at a Height of 0.75 cm...... 11^
33~h. Absorption Spectrum of Thiophene at a Height of 0.75 cm.. 115
3l-a, Absorption Spectrum of the Oxyhydrogen Flame at a Height of 2 cm...... 116
5k-b. FI ame Absorption Spectrum of Pyridine at a Height of 2 cm...... 1 1 7
3^-c. Flame Absorption Spectrum of Tributyl Phosphate at a Height of 2 cm...... 118
3^-d. Flame Absorption Spectrum of Thiophene at a Height of 2 cm...... 1 1 9
3^-e. Absorption Spectrum of Thiophene at a Height of 2 cm 120
35-a. Flame Absorption Spectrum of Pyridine at a Height of 3 cm...... 121
35-b. Flame Absorption Spectrum of Tributyl Phosphate at a. Height of 3 cm...... 122
35~c. Flame Absorption Spectrum of Thiophene at a Height of 3 cm...... 123
3 6. Absorption Spectrum of Pyridine...... 12^
37. Absorption Spectrum of Thiophene...... 125
3 8-a. Tungsten Lamp...... 127
38-b. Flame Absorption Spectrum of Benzene at a Height of 0.75 cm...... 128
x FIGURE PAGE
3 8-c. Flame Absorption Spectrum of Butyl Alcohol at a Height of 0.75 129
3 8-d. Flame Absorption Spectrum of Pyridine at a Height of 0.75 cm...... I30
3 8-e. Flame Absorption Spectrum of Tributyl Phosphate at a Height of 0.75 cm...... '...... *...... 131
3 8-f. Flame Absorption Spectrum of Dimethyl Sulfoxide at a Height of 0.75 Cm...... 152
3 8-g. Emission Spectrum of Pyridine from the Unmodulated Flame at a Height of 0.75 cm...... 153
39~a. Flame Absorption Spectrum of Benzene at a Height of 2 cm...... 134
39-b. Flame Absorption Spectrum of Pyridine at a Height of 2 cm...... 135
39-c. Flame Absorption Spectrum of Tributyl Phosphate at a Height of 2 cm...... I36
39-d. Flame Absorption Spectrum of Dimethyl Sulfoxide at a Height of 2 cm...... 1 3 7 lO-a. Flame Absorption Spectrum of Pyridine at a Height of 3 cm...... 1 3 8 lO-b. Flame Absorption Spectrum of Tributyl Phosphate at a Height of 3 cm...... 139
Ul. Flame Absorption Profile at 309.nm...... Ill
12. Flame Absorption Profile at I3I.nm...... Ill
13. Flame Absorption Profile at 168.nm...... 112
11. Flame Absorption Profile at 5 16.nm...... Il2
I5 . Flame Absorption Profile at 38 6.nm...... H 3
16. Flame Absorption Profile at 33^.nm...... H 3
17 . Flame Absorption Profile at 216 nm ...... Ill
18. Flame Absorption Profile at 259 n m ...... Ill FIGURE PAGE
)|-9. Flame Absorption Profile at 327 nm...... 11+3
30. Flame Absorption Profile at 3 2 8 nm...... 145
51. Absorption of the A1 308.2 nm and 309-2 nm Lines by the Oxyhydrogen Flame...... 148
52. Absorption of the Bi 306.8 nm Line by the Oxyhydrogen Flame...... 14-9
53- Absorption Produced by Spraying Nitroethane into the Oxyhydrogen Flame of Lines from the Ca, A 1 , Mg Multielement Hollow Cathode...... 150
54. Absorption Spectrum of Benzene...... 166
55- Absorption Spectrum of Anisole...... I6 7
5 6. Absorption Spectrum of 1-n-Nitrohexane in 10^ Ethanol...... 168 ABSTRACT
111 craviolo t emission and absorption spectra of oxyhydrogen flumes into which organic compounds were introduced have been in- vustigated in order to add to the knowledge of spectral interfer ences encountered in the analytical methods of flame photometry and atomic absorption spectroscopy. The information obtained will also aid in the elucidation of chemical and physical processes that occur in flarr.es and in the development of analytical procedures for deter mining organic materials in flames.
The most prominent emission and absorption bands that were found in the spectra are listed according to the wavelengths of band maxima and the species emitting or absorbing.
Emission, spectra indicated the presence of molecular fragments in the flames. Absorption of energy from sources of continuous emission (e.g. a hydrogen lamp) and sources of atomic line emis sion (hollow cathode lamps) indicated the presence of whole mole cules in the flames in addition to molecular fragments.
Comparisons wore made between the spectra, produced by the dif ferent compounds studied.
The effects of flame height on the spectra were investigated, and flame emission profiles and flame absorption profiles for or ganic and inorganic fragments are presented.
Effects on the emission spectra of varying the hydrogen to oxygen ratio in the flame and of aspirating the compound into the
xiii flame with hydrogen instead of oxygen were studied.
Estimates of detection limits were obtained tor ethanol and pyridine by measuring the intensities of emission from CH and Nil fr agments.
Tables are presented showing absorption of emission from hol low cathode lamps by flames into which organic compounds were in troduced .
The ultraviolet emission and absorption spectra observed were related to the atomic and molecular species formed in the flame from the flame gases (oxygen and hydrogen) ana the various organic compounds that were studied.
xiv IX'i'RO Dli CT ION
A. (IHNKUAh REVIEW 01’ FLAMES A:.1!) EL-li: ERGCESEKS
1. c;i!n; i Laek;■,rotiiiiI
Flames are amon;- Lhe oldest processes utilised by man.
The inves Liga cion of flames has progressed from the firs t use of fire in the stone age to an important position today in the fields of high temperature processes, flow systems, thermal conduction, molecular diffusion, the design and performance of combus cion engines and cham bers , fire excine tion, chemical kinetics, chemical synthesis, and analytical chemistry (1 -1 2 , 6 l).
2 . F 1 a m c S i :> e c S r o s e o p y
Emission and absorption spectra of flames have been collected and studied for some time (o, 7, ly-29, 31, IS). Results of flame spectroscopic studies provide information on species exist ing in the flame and thereby aid in the elucidation of the physical and chemical processes that occur in the flame.
Some of the most outstanding work in the field of flame spectroscopy has been done by Gaydon (id, ip, 19, 29). The first chapter of his book (19) begins with the statement:
"The chief distinction between combustion and
ocher chemical reactions is the occurrence of a
visible flame, that is the emission of light.
It is therefore natural to expect that investi
gations of the quality and quantity of light
1 emitted by ilames will form an important: part
of tiia study of combustion processes . " 1
Flames containing organic materials have been studied
to some extent. However*, so far there has been relatively little emphasis on analytical implica tions, in particular with respect to
interferences encountered in flame photometry and atomic absorption a na 1 y s e s .
Detailed descriptions of spectra produced by flames containing organic materials are found in the references cited.
Prominent features in the emission spectra from hot flames (>1 0 0 0 ° K )
include bands produced by excited fragments such as Oil, CH, Co, MO,
NK, CN , PO, PI I, C S , SH , and CC1. Corresponding absorption spectra of promixed flames are experimentally difficult to obtain due to the narrowness of the reaction none in which the fragments exist, the de flection of the source beam from the reaction zone by temperature and refractive index gradients, and the requirement for instruments of high resolution. Low pressure flames offer better opportunities for the investigation of reaction zones, as the reaction zones are much thicker in these flames than in flames at atmospheric pressure.
Failure to detect fragments can be caused by small concentrations or the lack of suitable quantum mechanical transitions within the spec tral region observed.
In addition to band spectra resulting from transitions between quantized molecular electronic levels, flames produce line
“Gayd a, A.G., Thc Spec Lroscopy of Flames, John Wiley and Sons, Inc., ipo'/', p. 1. •/
s'X’ctra resulting from Lrans itions between quantized a toirde or ionic
energy states. Spec tru over relatively wide wavelength regions are
also observed. These are possibly wide band spectra. (2 7), or arc
possibly produced by transitions in which at least one or the states
involved is unquantized such as by association and dissociation pro
cesses involving molecules, ions, and/or electrons.
The similarities between spectra obtained from flames
containing organic materials and from comets allow extensions to be
made of results from flame spectroscopy to the field of astrophysics
(l‘b , b - 0 -
b. Some. Energy Aspects of Flames
Spectra provide information concerning the identity,
concentration, and energy of the species emitting or absorbing, (6 ,
12, 17, 20, 21, 25, 2 6 , bO->i-, 6 0 , 61, 109, 176).
Line and band spectra in the visible and ultraviolet regions involve electronic excitation. Electronically excited spe cies are produced by the absorption of electromagnetic radiation at
the required frequency, by collisional activation, by transfer of energy from electronically or vibrationally excited species to un excited species, by triple collisions where two species combine and transfer their excess energy to a third, and by chemiluminescent pro cesses which are defined by Boiteux as
"arising when the emitting species is formed in
a chemical reaction directly in an excited state" . 2
^Mavrodineanu, R. and Boiteux, H., FI ame Spectroscopy, John Wiley and Sons, Inc., I9 6 5 , P- 5^5- Thu electronically excited species thus produced are
able to lose their excess energy by radiation:
where E. - E. is the energy of the quantum of electromagnetic radia- J tion emitted by the species, which goes from an excited state with
energy above the ground state to a state of lower energy, E ., h
is Planck's constant, and v is the frequency of the radiation. Radi
ative deactivation requires on the order of 10 sec., which allows
time for numerous collisions to occur in flames at atmospheric pres
sure (b, lh-, pp 3 130). Excess energy can be lose by collisions with
atoms or molecules, in which case the atoms or molecules become elec
ironically excited, ionised, dissociated, or chemically reacted.
Electronically excited species can also lose energy by collisions
with free electrons in the flame, in which case the kinetic energies
of the electrons are increased.
It is evident that the inter-related processes of
electronic excitation, emission of radiation, and collisional de
activation are complex.
The intensity of emission for a particular quantized
transition is proportional to the number of excited atoms or mole
cule s , ^j-7 ) -
I - A. . hvN. (2.) ij 1
where I is the energy emitted per unit time, A . . is the Einstein Lran:;ition probability o.L spontaneous emia.s ion, and N. is the number
ol a Loins in the excited s ta Le, i. When the system is in thermal
equilibrium, principles of statistical mechanics can be applied to
obtain a rela tionshin between the number of excited atoms, N. and x the total number of atoms, N.
-E . / kT \r N ai° 1 , (3.) i v -E./kT J °j J whore g^ and g. are the statistical weights for energy levels i and j
respectively and k is Boltzmann's constant. In the ordinary flame
used for chemical analyses all except a negligibly few atoms are in
the ground state (60).
-E./kT ~ -E /kT ~ n ^ t*i»J ~J 1 ‘ V 0 * «<> (’ h where g is the sta.tistical weight of the ground state, and E is the o o energy of the ground state. Eq 3 i-s reduced to
- E ./kT g e r N. = N — ------(5 .) i. cr
By combining eq 2 and eq 5 an expression for the intensity of emis sion of an excited species existing in a. thermally equilibrated sys
tem is obtained.
. . ... -E./kT A . hv h g . e i It - 10 —— L (■' (o.) \ °o
The effect of self absorption has been neglected. However, atomic u
and molecular electronic spectra produced by flames usually involve
the ground state, and self absorption should be considered.
The equality of variously determined temperatures at
a sufficient distance above the reaction none of a premixod flame in
dicates that thermal equilibrium is achieved in the outer cone. In
this region of the flame the application of eq 6 is valid, where T
expresses the temperature of the flame. In flames at atmospheric
pressure the probability of radiative deactivation is very small
compared to the probability of collisional deactivation (6 0 , I J & j .
Thermal equilibrium does not exist in the inner cone,
or reaction cone of the premixed flame. This zone is characterized
by thermal-, excitation-, ionization-, and chemicai-disequilibria which lead to "overexcitation" and "overemission", i.e. to higher
concentrations and to more intense emission than would be expected
for equilibrium conditions (IT)- Eq 6 is not applicable. Low pres
sure flames offer better opportunities for the study of nonequilibri um processes than flames at atmospheric pressure because of their
thicker reaction zones and decreased rates of collision of species in
the flames. Inner cones of organic flames are characterized by strong emissions from excited organic fragments such as Cil, indicat ing an "overexcitation" of these species. The OH fragment emits strongly in the outer cone as well as the inner cone. The emission in the outer cone probably arises from thermal excitation.
K . Chemical Reactions in Flames
Flame chemistry involves chain reactions and radi cals Tj 10 j 12, f2, 5b 3 5 6 ). The relative concentration of radicals is small: 10 2 -l0 2 mole fraction. A typical distribution of flame species might be m o l e c u l e s , rad icy is end a t o m s , end ions in
die proportions 1 : 10 ‘‘ : 1 0 f, (1 ), where the term molecule refers
to n polyatomic species that is sufficiently stable to exist at
ordinary tempera Lures and pressures and the term free radical re
fers to an electrically neutral molecular fragment having one or more unpaired electrons. Considerable work has been done on the
study of ions (yd, 99) and radicals (l, 9 , 1 2 , 1 7, Id, y k , yj) in
f l a m e s .
Since electronically and vibrations 1iy excited species affect flame processes, spectroscopy is a useful tool for studying
flame reactions.
Hydrocarbon-oxygen flames have received considerable attention. In oxygen-rich hydrocarbon flames the predominant re actions can probably be represented as (l)
OH + C H , _ la- KeO + C Re- C , „ + CKS . n 2 n+ 2 n 2 n-M n-a. 2 n - 2
It is probable that the unsaturated hydrocarbons react with oxygen atoms and that Cl-I3 is oxidized to 1I2 C0, which is the main oxygena ted intermediate compound that is observed. It is found only in trace quantities. Reactions occurring in fuel-rich hydrocarbon flames are more complex. As the fuel to oxygen ratio is increased, there is a gradation from initial attack on the hydrocarbon by OH to initial attack by II. Recombination of ra.dica.ls to form hydrocarbons, in cluding hydrocarbons of higher molecular weight than the original fuel, are important. Formation of oxygenated compounds is also im portant. In very fuel-rich flames large quantities of carbon are produced (2 , 6 , 1 0 -1 2 , l A , 2 7, AO-Ac). The formation of solid carbon in flames is industri ally impor tan h with regard to flame luminosities, soot deposition, and the manufacture of carbon black. The formation of solid carbon aceous compounds is determined by the chemical and physical condi tions in the flame. Theories on the process include the two ex tremes of organic fuel breakdown to C or followed by polymeriza tion and of initial polymerization and condensation of the fuel followed by dehydrogenation.
Considerable work has been done studying reactions occurring during slow' combustion and in cool flames, that is, study ing combustion reactions at temperatures of less than 1000°K , (c,
7, 10, If-, 12, 3 f-7-50). Carbonyl compounds, peroxides, hetero- cyclics, aroma tics, and other complex intermediate combustion pro ducts arc formed, depending upon the system studied. Emission from excited formaldehyde characterizes cool flames of hydrocarbons. Re sults obtained from the study of slow combustion processe-s and cool flames cannot in general be applied to high temperature fla.me reac tions, that is, to flames of temperatures greater than 1000°K.
B. GENERAL REVIEW OF THE USE OF FLAMES IN CHEMICAL ANALYSIS
1. F 1ame Photo me try
a. The Principles of Flame Photometry
Kirchoff and Bunsen (5 1 ) in the middle of the nineteenth century demonstrated the analytical usefulness of the flame by the discovery of rubidium and cesium. Lundegardh (52) generally receives the credit for introducing the analytical method of flame photometry (9 , 17, •
In flame photometry a solution containing the element olr intores L is sprayed into a flame where the a toms become
excited and emit electromagnetic energy. The frequency and intensi
ty of the energy emitted serves to identify and to measure the con
centration o i. the element emitting (eqs 1 and u ). Although the prin
ciple is simple, many experimental parameters must be considered be
fore the emission signal can be quantitatively related to the cle
ment in the original sample with any valididy (9 , l''f, 6 9, 71 > 162).
Calibration curves are employed. Standard and sample solutions should
be as similar in composition as possible, because differences can
produce chemical variations in the solutions, variations in aspira
tion rates due to surfa.ee tension- and viscosity-differences, and
variations in the processes that occur in the florae.
When the sample solution reaches the flame a
complex sequence of processes begins. The solvent evaporates, the
solute is dissociated and vaporized, and the atom is excited and
emits. There are numerous opportunities for variations in analytical
data. Critical parameters include the rate at which the solvent evaporates or burns a.nd the rate at which the solute dissociates.
Organic solvents are generally advantageous from the point of view
of rapid evaporation or burning, and organic addends, in particular,
facilitate solute dissociation since the organic portion of the so
lute burns, leaving the free metal atom. Hieftje and Malmstadt have
described an cxpcrimental system for observing the sequence of events
that occur when a sample droplet travels through a flame (7 2).
The analytical signal in flame photometry is de pendent on the part of the flame observed. 10
b . 'I n l:o r i~( ■ 1'i.ti'i 1 in Quantitative Flame Oho c o m . 1 tr ic Anal v;- is
(1) Chemical Inuuricrcmccs in Flame 1'ho tome try
Interferences in flame photometry that are caused by chemical reactions in the flame include ionization and the
formation of undissociable compounds such as oxides or phosphates.
Failure to decompose the solute containing the element of interest can also cause a serious inter hre.icc. These three interferences result from a decrease in the number of atoms in the flame with re spect to the theoretical maximum number. Chemical reactions that occur between flame and sample constituents depend upon the type and ratio of gases used to produce the flame, the oxidizing or reducing character of the flame, the temperature, and the components intro duced with the sample. Ionization is generally increased by increas ing the flame temperature. Dissociation of refractory compounds is generally facilitated by an increase in flame temperature and by reducing conditions. In some instances emission from a stable com pound (e.g. an alkaline earth oxide) can be used to determine the concentration of the element of interest.
(2) Spectral Interferences in Flame Photometry
Spectral interferences in flame photometry are caused by (l) varia l-xoiis in ui’iC flame backgx'ound emission (e.g. some organic solvents increase the background emission of flames),
(2 ) the superposition of line, band, or continuous spectra over the spectrum of interest (e.g. calcium hydroxide emission interferes in the determination of sodium), and (y) absorption (i.e. a decrease in the emission intensity due to the absorption of radiant energy by 11
other species in the illame). Figure a. shows a portion of the emis
sion spectrum of manganese superimposed on the background emission
from the oxyacetylene flame
Specific examples of spectral interferences
in r 1 a me piio tome try inclueo she interferences of GH omission w'rth the
analyses for bismuth at yGb.b nm (ip^-), for magnesium at 2 o p .2 ran (5 5 ) >
and for copper at 527.7 11m and 5 2 7 * 1 nm (125), and. Che interferences
of C 2 and CH emission produced by organic fuels or solvents in the
analyses for lanthanum (55), chromium (5 5 )3 an^ metal chelates (162).
2. Atomic Absorption
a . Tlie Principles of Atomic Absorption
The introduction of the analytical method of
atomic absorption spectroscopy was due mainly to the work of Walsh
(75).
In this technique (9 , 1 7, 5 7 , 5 8 , 6 5 , JO , 75-725,
loO, log, lOo, 1 8 2) a flame (most commonly) is used as a means of
producing neutral atoms. The quantity of electromagnetic energy that
the atoms absorb is related to their concentration. The principles
of conventional spectrophotometry are applicable to atomic absorption.
7v = lQe V (7-) where I is the original intensity of a beam of monochromatic paral
lel rays, Iv is the intensity of the beam after it has passed through
°Dean, J.A., Flame pho tome try, McGraw-Hill Book Co., Inc., i9 6 0, p • 2-i-p , e io * lo— -r. 12
5 lO 56 0 5 8 0 60 0
Fig. I.3 Flame Emission Spectrum Produced by Manganese Super
imposed on the Background Emission from the
Oxyacetylene Flame
( ) Emission produced by Manganese
( ----- ) Background emission from the oxyacetylene flame an absorbing laediuui of thickness i , and kv it; the absorption coeffi cient of the medium and depends on the properties of the medium and on the frequency, v. One must be careful, in. interpreting oq '{ with respect to flame work because in this instance the absorbing medium, the. rlnme, is a dynamic system whose properties vary with the por tion or the flame observed. 'ihe concentration, of atoms varies from point to point in the flame and depends very markedly on flame con ditions, that is, on the physical and chemical processes that are occurring in the flame. The integrated absorption is proportional to the number of absorbing species
r'j
/ k^ dv = me..
where e is the charge of an electron, m is the mass of an electron, c is the velocity of light, f is the oscillator' strength of the transition involved and N\j is the number of atoms capable of absorb ing radiation of frequency, v. For practical purposes Nv is the to tal number of atoms in the flame. (See page 5 °f this thesis.)
Calibration curves are used for relating absorp tion signals obtained in analyses to concentrations in original samples. As in flame photometric measurements, standard and sample solutions must be alike to minimize variations in aspiration rates and flame reactions (ph, 8p , 80). The portion of the r 1 c-fiiti 0 0 S 6 itv£d is critical in atomic absorption measurements, and the optimum flame height for absorption studies does not necessarily coincide with the optimum height for emission studies (8 1).
b. Interferences :i n Quantitative Atomic. Absorption Ann 1 • ’ s ( 1 ) (an -i.i i c ! 1. n tv . w , v ;1 c < ■s in At:r,i.:ic t i on
Chemical interferences in atomic absorption
are analogous to those encountered in flame photometry. Failure to
decompose the solute containing the element of interest or the forma
tion of undissociable compounds in the flame decreases the number of
a toms ennoble of producing a mensurcablc signal (71, 82, l-S-9 ). Ioni
sation is minimized by proper control of the flame temperature. The
effect of variations in flame temperature is less important in atomic absorption than in flame photometry except as the atomization process
(the production of atoms of the element of interest fromthe sample
solution) is concerned (100). The most important function of the
flame in atomic absorption is to produce a population of ground state atoms from the sample solution, and chemical processes in the flame
that tend to change the population of ground state atoms produce in
terferences in analyses*
(2) Spectra] Interferences in Atomic Absorption
Spectral interferences (emission or absorp
tion signals produced at the wavelength being studied by species in
the flame other than the one of interest), are generally considered
to be less of a problem in atomic absorption than in flame photome try .
The source beam from the hollow cathode lamp
v.rost commonly used), vapor discharge lamp, electrodeless discharge lamp, spark, continuous lamp (83, 109, 122), or flame (fa, 73 j 87) is usually modulated and should be the only radiation detected by the instrument. However, intense flame emission can produce noise or saturate the detector (8l, yy, 9 8, 166, I9I ). Noise produced by ilaino c./.is a ion can be minimized by using narrow slits -
Scattering and absorption of the source beam are produced by droplets, solid particles, flame gases, organic sol vents, and molecular species in the flame that are produced from the sample and the flame constituents (l 7 , 9 6, 81, by, 64, o'j, 9 5 , 94 > go, 98, 101, 102, 104-107, 111, 112, 119, 121, llg, 124, 1$2 , IcO, log, loo, lo2, lOo). These effects are dependent on wavelength.
Flame gases absorb at low wavelengths. Organic solvents produce ab sorption signals at wavelengths less than 2$}G run (94, 105)- Molecu lar species produced from the sample can absorb (op, 9I , 9u , 1 0 7)I for example CaOil will absorb the resonance line of barium (8p).
Scattering and absorption interferences are intensified when the source beam is passed through the flame more than once or when tubes are used to extend the path length of the flame (po, 61, op, 8b, 69 > go, 101, 107, H I, 1-2, 119, ido, lo2, loo).
Koirtyohann and Pickett (96) propose that some of the effects described in the literature as being produced by scattering cannot be attributed wholly to scattering because of their relatively large magnitude and their variation with wavelength. They propose that absorption by molecular species in the flame (op), vari ation. of the refractive index within the flame caused by vaporization of sa.lt particles, and continuous absorption, due to ionization of a- toms are also imp or tar. . They observed maxima and minima at the same wavelengths (within experimental error) for absorption and emission runes produced in 1 lames by potassium halides and alkaline earth oxiues uUcI nyaroxides (op).
Nitric acid produces NO absorption spectra i.n flumes (i.'i 1 _), and sulfuric ac i.d pi'otiuc^:; 0 0 ;. i:l>!ior;>tii>n ;;jn/CLra
(i.Lr, ix:;, Ip::). Fuwa and Vailco ha.vc measured mil fur concentration
by the SOo absorption produced 1 :-. an air-hydrogen flame (i^L').
Absorption scans produced by hydrogen-air, propane-air, and acetylene-air blames (yx) show chat absorption is severe a t wavelengths less chan nOw nm tor ail three rlames , a.nu tna t absorption is least intense for the hydrogen-air flame in the region between 200 and 2p0 am. Absorption scans produced by air-acetylene, a ir-hyer ogen , and argon-hyurogen flames (121) show' that absorption is
least intense for the argon-hydrogen flame, and most intense for the air-acetylene flame in the 200-2p3 nm region. Absorption by flame species makes analyses for elements with resonance lines at low wave lengths difficult (81, yi|., op , 9p, 9 4 , 10h-106). Chakrabarti (ICO) observed a dependence on the flame composition of the absorption of
the tellurium 119. p nm line by an air acetylene flame. With a total consumption burner and an extended path length (101, It .6), absorption by an oxyacetylene flame and the products produced in the flame from
the solvents was found to be dependent on the flame composition, liana and Humbly (rOu) observed appreciable absorption by. unignited acetylene-air mixtures at wavelengths less than 210 nm. At 209 nm they reported 009 transmission for the flame and dpi cransnissson for the unignited gas mixture. Unignited town gas was found to absorb the nine 2-p.d nm line appreciably (8 9). The interference was at tributed to absorption by CO and H 2 S . The town gas-air flame ab sorbed less than the unignited fuel. Koirtyohann ana Feldman (31) using fuel rich oxy’nydrogen flames with path lengths of 12-75 cm ob served marked absorption by flames. This was especially severe at 1'f
i. f-V. Ox U'ciVO 1 cu^Lhs ,
Absorption by Oil radicals has been observed in the loG-yyO nm region (31, 31, 93 > ^-32, lly, i b p 13b). Absorp tion of the bismuth yOo.c nm lino by C1I radicals in the flame has
seen reported (ol, o ’r, 9 A I 2 l ) . iiooymayers and Aihemade used a bismuth hollow cathode lamp to excite OH radicals in the flame in orcer to study quenching of radical fluorescence (lbs-).
Intense emission from the nitrous oxide jcotyicnc riame sit y fo* y nm interferes wrtn analyses for gndolmium
(yc). Oh emission interferes with analyses for bismuth at yG6.3 ant
XnCvjxTrci“tjriccs ociiv/ccn cigjuicciiii lines Iic.vg been found (db). Samples containing europium, which has a line at y l l . 7 5 3 rim, will absorb the copper yll.Jyl nm line but not c-Iig copper yhT-yfb n[n line (do). Hanning and Fernandez (117) report that the coos.lt line at lyy.oAy nm is probably the cause of the interference when determining mercury at lyy.oyl nm in a cobalt matrix. Such spectral interferences can possibly be eliminated by using a mono chromator with high resolution (113). Such interferences can be
Uuij-izod however; tnc use of an iron noflow cathode lamp (j—■-1 , iHp ) and the use of a uranium hollow cathode lamp (yO) as sources in atomic absorption have been proposed. The complex spectra of iron and uranium makes possible the coincidence of iron and uranium lines with the analytical resonance lines of numerous elements,
y . A f o m i c Fluoresce n c. a
a. The Principles cf Atomic Fluorescence
The analytical method of atomic fluorescence was demonstrated by Robinson in lyol (l2y). The method was developed as ;ai diKily Lieul technique by V/inofordt.iur aad Vickers (ih’O).
in th is mi.'. L’nou (.l.L , 9y , \)[) , -A i~-Ly
Lo nbtuvrpt Lon spec troseopy, the i lame (;;ios t commonly) in used to pro duce a population of neutral a toms in the ground s ta te. Tile atoms aosoib i. a cl iai t .l o 11 at lIic ruqe ireu rrcquency a r o .a an aoprcpricte source and than re-omit their excess electronic energy as radiation of the scale frequency as the radiation absorbed or of a frequency iov/er than
the radiation absorbed. The frequencies of,the emitted radiation can be used to identify the element emit tine,, and at relatively low atomic concentrations, the fluorescent intensity is directly propor
tional to the concentration of atoms in the flame (125, 127’)- For a riven line of a metal vapor in a flame of constant composition and tempera.ture ,
I, - CF°N (9 .) JL U where I,, is Che intensity of the fluorescent emission, C is a con* r stant (125) , P° is the incident radiant power, and N is the number of ground state atoms, which is very nearly equal to the total num ber of atoms in the flame. (See page 5 of this thesis.)
As in flame photometric and atomic absorption methods, calibration curves are used to relate analytical signals to concentrations in the original samples after various parameters are considered (fl)-
Flame species and flame temperature affect the extent of nonradiative deactivation of the excited atoms (51, 1 2 6 , lio, IpO, lyl, lyo). Total consumption aspirator-burners have been found useful for fluorescent studies (126, 2'b, lpl, lyo). The i i uiH'oiiCdiCi.' s .i.gnn. 1. 1;; <_i v- pe iuL: 11 L o n the I: J a me i 11- i.;1) L a n cl die L'/Vl: o f
Llume dial: i.s used.
oincu it in experimental]y easier to iiKranure the
emission intensity oi a small signal , such as occurs in atomic fluo
rescence , than it is to measure a small decrease in an emission sig
nal, such as occurs in atomic absorption, it may bo possible to ob
tain better sensitivity with the fluorescence method (93a 13#). In
absorption measurements tne absorbance is related to "log (r /Av j ,
ec: The fluorescence intensity is directly proportional to the in
tensity of the source, eq CJ, and can be increased by increasing the
source intensity (lyh).
Organic solvents enhance the fluorescence signed.
This effect has been attributed to more efficient aspiration and ato mization processes (oi, 1 2 9, l;3f).
b . In ter f i:renccs in 0 11a n I:t.a 11 vo A tomic FI uores cenca A n a l y s is
(a) Chemical Interferences in Atomic FI e.orescence
Chemical interferences in atomic fluorescence are analogous to those encountered in flame photometry and atomic ab sorption. Chemical processes in the flame that tend to change the number or atoms produce chemical interferences in analyses.
(2) Snectral Interferences in Atomic F]uorescence
Absorption and scattering of light in the flame produce interferences. High background emission from the flame can produce noise and a. non-linear response of the photomultiplier to tne a c fluorescence signal (9 9, 123, I p y » !;&)•
b . The Do torminatfon of Nonmetals by Flame Photometry and Atomic A o s c rption Flame methods for nonmetals include direct and indirec
techniques.
In direct techniques (bg, iJ-, l>.h, 1 y'J, I'ly, IbY, IfG,
■v-j Iff j , ieV,', Ilf) the intensity oi the omission produced by
the clement or a compound of che element is measured. Examples in clude the analysis for phosphorus by measuring the intensity of the continuous emission produced at phO nm or by measurement of the irvten sity of the PO band at lYo.Y nm (lpl), analysis for nitrogen by meas uring the emission from CN or NO fragments, the analysis for chlorine by measuring CuCl emission, the analysis for sulfur by measuring CS emission, and the analysis for organic compounds by measuring CH and
Co emission. Approximately G.Old 0f an alcohol can be detected by
CM and Co emission in hydrogen flames (1 7 5 ). Recently cool flames
(~ p10-iip‘3°K) have been used for flame emission studies of compounds containing sulfur by measuring emission from the S2 fragment at y8Y nm (lYy) and of compounds containing phosphorus by measuring emis sion irora liPO at gfd nm (lYb), and also of tin (op). Phosphorus and sulfur can also be determined directly by measuring HPO and So band emission from fuel-rich air-hydrogen flames (10 7). Sulfur has been determined by measuring the absorption by S02 produced in an air- hydrogen flame (I5 2 ).
Indirect techniques (5 3 , 61, 9 6, 1 ^ 5 - 1 ^ 9 ) include quantitative reactions in the sample solution with subse quent measurement, directly or by difference, of the weight of metal that reacted with the nonmetal. An example is the decrease in sig nal from a solution containing silver ions after reaction with bro mide. Chemical interferences or changes produced In the flame by Liu.' nonmeLa1 v/hj.oii al J.o.c t Liu: ,i; pi;;!. o i. ;m u ppruprLu metal c.-in
uXtio be utilized (1;'/;'). An example :Ld the analysis for ohos pnorus
by measuring the inhibition to calcium omiasion that it producer in
the. flame. Indirect techniques are also applicable to metals that
are difficult to determine or show low sensitivity by direct flame
me thods (Ifo , I f Y).
The principle of fl.-mo photometry has recently been
applied to the development of specific detectors for gas chromato
graphic s tudies (I5 5 -I5 9 ). Much of this w o r k involves nonmetals.
Thu principle of flame photometry has also been extended to the de
velopment of monitoring systems for metals and nonmetals (ipo).
The principle or atomic absorption has also been
applied to the development of specific detectors for gas chromato-
y j p m c s Lucres (1—ty j m
5 • Tin? Use o 1 O r e,ani.c Solvents in 1’ i.ame Photonie try , Atomic Absorption, and Atomic Fluorescence
Enhancements in sensitivity are observed in flame
pho tome try, atomic absorption, and atomic fluorescence analyses when
organic solvents are used instead of aqueous solutions (5 5 > 55 > 5 o ,
J J 3 , (0 j i ‘ r ( .j IbvJ — f (I) , lop ) .
Probably the most important cause of the observed en hancement is a more efficient atomization process in the flame; i.e. a more efficient process of producing free atoms from, the sample so lution. Organic solvents evaporate (or burn) more rapidly in the flame than does water. Thus the solute is freed from solvent more readily when organic solutions rather than aqueous solutions are used
The solute is then dissociated and vaporized. Organic chelates lac 1.1 italic solute dir. sou in Lion incu the or;;;:nic por tion burns ,
Iu.aving the metal i Lv)Dis i_ree Lo ijuco.se excited or to absorb.
Other rue Lora that may be ol imp or tance in increasing the sensitivity of flame methods when organic solvents are used in clude the rate at which the sample solution is aspirated into the flame and the site of the d r o p s „ Generally there is less cooling of the flame when organic solutions are sprayed into the flame than when aqueous solutions are used. This effect and the possibility of cnem- iluminescence (pages p and 2 p of this thesis), may produce increased sensitivity in flame photometry when organic solvents are used.
Advantages of extraction procedures (55 s 59 » 1^7, l e k , l o p , l o 7, IfO-lTp) include concentration of the desired component in to a smaller volume of solution, removal of the desired component from other sample constituents which could produce interferences, the increased efficiency of atom formation when metal chelates are used, i.e. the organic ligand burns in the flame leaving the free metal atom, and the enhancement in sensitivity produced by the sol vent that is used for extraction.
When organic solvents are aspirated into the flame the background emission is greatly increased. This effect must be con sidered when making flame photometric measurements and may increase noise problems in atomic absorption and atomic fluorescence spectros copy. In addition to increased background radiation, new bands may appear. This is particularly important when measurements are taken in the reaction zone, because emission and absorption by organic frag ments are most intense in this region of the flame. Also absorption and scattering by the flame are generally increased when organic solvents are used, particularly ia reducing flame a. Tne use oi
organic solvents may also al cor the part of die flame that is optimal
for analytical measurements (1 6 0 , 1 6 2 , Iff).
Oxygenated solvents such as ketones and esters have
been round especially useful for flame methods (gy, l6 f), although many otners are used as well, iiromtic solvents produce a relative"
o.y unstable flame background (pp, lei-). Some halogen-containing sol vents, especially CCl.-^, do not produce the high degree of enhance ment found for other solvents (of, cl).
6 . deducing Flame.:; are Chcnrili.minescence
Two flame techniques have been developed recently which lend to increased sensitivity; chcm i1 utr.inescenca flame spec
troscopy and the use of reducing flames (if, 2 y , ly6 , 5 9 1 , C r(, 1 0 7, sic, 1 -r f , r jo , -t (■—If o '). m e r e seems to be a corre 1 ation be tv/een the presence of organic material and the "overexcitation" phenomena (page
6 of this thesis) of metal additives (17, 17^-176). A distinction should be made betv/een chemiluminescence (page y of this thesis) and a more efficient process of producing atoms in reducing flames. Chemil- uminescenco is indicated by an increase in emission intensity with no change in absorption intensity. It is possible for the general equa tion expressing the reaction of a metal with oxygen in the flame,
metal + oxygen = oxide,
to be shifted to the left in reducing media.
In 1 8 7 7 Gouy (193) described the differences in the emissions from the inner and outer cones of a prcmixed flame, lie observed that "Ylu' blue cono oi: a flume possesses a pi-culiar
o!v.iSw ion power" ,‘L
Tiic rone cion cone of the flame can bo used for analytical Wurk as
lony as a. reproducible a ignal is produced even chough thermal equili
brium does not exist in this part of the flame (.i'f J .
1' uo l r icn rlames may produce enter ferences rn atomic
absorption and atomic fluorescence measurements because of their in
tense background emission, especially when organic solvents are used.
In emission w o r k instruments with high resolution are necessary to
separate the emission of the element of interest from flame background
emission (I7p , 1 7 7, led).
C . PARPOSF OF The INVI.SVIGATICh REPORTED IN THIS THESIS
The importance of flame spectroscopic studies has already
been discussed with reference to the elucidation of the chemical and
pays ica i processes that occur rn flames. ihose processes determine
the usefulness of flames for analytical purposes. Proper understand
ing and utilization of factors effecting rlarne processes are nec
essary for obtaining optimum experimental conditions for analytical
w o r k (9 , 1 7).
Spectral interferences caused by flame background emission
and absorption have been mentioned. As Boiteux states
"The spectra of the elements supplied to the flame
will be superposed on the spectrum of the flame itself".D
‘■Mavrodinoanu, R. and Boiteux, H. , 71 a me Spectroscopy, John Biley and dons, Inc., I 9S 9 , p. g y .
"Mavrodineaviu, R. and Boiteux, 11., Flame Spectroscopy, John h -L 1 y Ll LLU lJ *J I I t , iiilC g , « 'J p , p . C— y . Jin or nor to obturn Liccuin results from iJ.an.u pho tonic tr rc , u Loiuic absorntion, and atomic fluorescence i,:c;nnii\.:!i,^ntK ; the analys t mus t have know Ledge or the background :,;x:c trr produced by Lhe flame y j s c s ,
the solvent, and blit.' cons tiUieuts of the. s a m p l e .
The purpose of this investigation was to study the back ground spectra produced by organic solvents in oxyhydrogen flames.
Results of such a study should be useful in the elucida cion of the chemical and physical processes occurring in flames, i.e. the com bustion reactions of organic compounds, the mechanisms of the produc-
l ion or atoms and other specres rn flames, and tire excitation or
these species in flames. Results of this investigation should also
indicate sources of spectral interference in flame photometry, atomic absorption, and atomic fluorescence methods. The investigation should also aid in the design of analytical flame procedures for organic compounds (page 20 of this thesis), (2d, iyO).
Several emission spectra (2d, bl) produced by aspirating organic solvents into oxyhydrogcn flames, and an absorption spectrum
(oi) produced by spraying acetylace tone into an oxyhydrogen flame have already been reported. DESCRIPTION Oi’ KXi’HRIitEN'i’AL CON'D IT IONS
A . U_ itr id"hPN AC Tiiri GOU’TUUhT GEE!)
The data rep or led in this invus tiga.tror. were obtained with
a lieckiiuin A comic Absorption Assembly, cons is Lina; oi the Lamp Power
Supply, Gas Regulator Unit, Mode a. A ’b- G Spec trophotome ter , Ten-inch
Laboratory Ponentiome tr ic Linear-Log Recorder, Scale Expander, and
a’: Turbulent Flow burner Assembly with one burner in the central posi
tion, as shown in rig. 2. In audition, a small number of emission
spectra were obtained with a Beckman DU Quarts Spectrophotometer
equipped with a Flame Photometry Attachment and a Spectral Energy
Recording AGap ter.
Tiie burner used for all oi the work was a small-bore Beck man tota.l consumption burner (if; 33 > 1 1 0 ). It is a direct atomiser as opposed to an indirect one, that is, ail of the sample solution
is aspirated directly into the flame without passing through a ser
ies or tubes vine re the larger drops are discarded. Thus a relative ly large volume of solution reaches the flame, as shown in Table VII.
The sires of the drops reaching the flame vary, and a significant num ber of drops pass through the flame without being completely evapo rated. The flame produced by the total consumption burner is a turbu lent diffusion flame in which there is more intermixing of the flame zones than in a premixed flame (If, 33). Effectively the reaction zone is larger than in a premixed flame (I7 5 , 1-95). True diffusion flames are obtained when flow rate., are slow. Fas tor flow rates cause more Lamp * Lens Chopper Flame ** Lens Monochromator
Fig. 2. Diagram of the Equipment Used
*Aperture for absorption studies with the hydrogen and tungsten lamps.
**Aperture for flame emission profile studies. 28
turbulence and more premixed character in the flame (l^)* The use of combustible organic solvents further complicates the flame structure
(I9 6). Results (33) indicate that for oxyhydrogen flames the region of nonequilibrium is restricted to the reaction zone in the immediate vicinity of the burner.
A hydrogen lamp with the Beckman Power Supply Serial No.
PS^5^-“Model A, a tungsten lamp, and various hollow cathode lamps
(from Atomic Spectral Lamps, Pty. Ltd., Australia; Beckamn Instru ments, Inc.; and Perkin Elmer Corp.) were used in order to obtain the absorption spectra.
Hoke Flowmeters (62222 AAL and 62222 AAD) were connected between the gas unit and the burner, and Standard Liters per Minute of oxygen and hydrogen were read directly from the meters.
B. ORGANIC COMPOUNDS STUDIED
The compounds studied were cyclohexane, benzene, toluene, distilled water, ethyl alcohol, butyl alcohol, anisole, methyl isobutyl ketone, amyl acetate, acetic acid, butylamine, pyridine, nitroethane, nitropropane, ammonium hydroxide, tributyl phosphate, triethyl phosphate, phosphoric acid, ammonium dihydrogen phosphate, thiophene, dimethyl sulfoxide, chloroform, and butyl chloride (from
U.S. Industrial Chemicals Co., Matheson Coleman and Bell, Mallin- ckrodt, Allied Chemical, J.T. Baker Chemical Co., Fisher Scientific
Co., and Eastman Organic Chemicals). In general the solvents were reagent grade, containing 0 .0 0 2 ^, or less residue after evaporation.
Anisole, methyl isobutyl ketone, amyl acetate, butylamine, nitro ethane, nitropropane, tributyl phosphate, triethyl phosphate, thiophene, and butyl chloride were practical grade. yj
The compounds v/ci'c p.i)t purified prior to use.
C . i'ROUK:f ilb’,
Unless specifies otherwise , 4V-' s £ J. ow rate;; v/uro y.y 1/rnin. of oxj/piii end 10 i/min. of hydrogen. The samples wore aspire Led in to tlie Alamo v/i ch oxygen unless specified othervjise. i’or aspiration with hydropen the oxygen and hydrogen, gas linos wore switched at the b u r n e r .
Solvent aspiration races were determined by measuring the time required for spraying a. known volume of the sample into the f l a m e .
Desired flame heights Were obtained by positioning the bur ner so mat the beam from a. lamp focused on the lens leading to the monochrome.tor would pass through the vertical axis of the flame aft known distances above the tip of the burner.
if o.c Lf\o z L gaylg c \\\j _ fj e O proi:ile sliuuics g n g p c g l u it g wiiii g. l.o x C.c cm noriaontal slit was placed between the flame and the lens leudi . to the monochromator.
Absorption spectra were obtained for organic solvent sprays as well as for the flames by aspirating; the samples into the 1 ignt path with oxygen. The hydrogen flow rate was aero, and there was no rlame burning .
In order to determine v/hother any emission was detected from the unmodulated flames in absorption studies, the light from tlie lamp was blocked and any signal from the flames recorded.
For scanning over long tin periods, organic solvents were contained in a cylindrical glass tube approximately yO cm long and
70 ml in capacity with a small hole for the burner ca.pilla.ry in one end and a larger hole in the other end for sample introduction. For smaller periods of time, 5 or 1 0 ml glass beakers, covered with alum inum foil into which a hole was punctured for the capillary, were used. These measures were taken to prevent the solvent reservoir from catching fire.
The 200-650 nm region was investigated. In addition, some emission spectra were obtained up to 1050 nm with the DU Spectro- p’notome ter. RESULTS AND DISCUSSION
A. EMISSION SPECTRA
1. Wavelengths of Band Maxima and Identification of the
Species Emitting
The prominent emission bands that were observed are listed in Tables I-VI according to wavelength and species emitting.
a.. Emission Ba.nds Produced by the Oxyhydrogen Flame
Spectra from the oxyhydrogen flame exhibited bands of the 3 0 6.^ nm OH System (I9 8). See Tables I and VI and Figs.
10-a, 11-a, and 12-a. Bands at 930 and 9 7O nm are part of the vibra- tion-rotation spectrum of water (195 j 198). See Fig. 3*
Table I. Emission Bands Produced by the Oxyhydrogen Flame
wavelengths of band maxima (nm)* emitting species
262 OH
269 . OH
283 OH
289 OH
295 OH
307 OH
309 ' OH
3^3 OH
51 5 2
Continuation oi Table I
wavelengths oL; band maxima (nm)* emitting species
Oil
9 5 0 h 2o
970 h 2o
^Wavelengths were measured to + 3 nm.
b . Emission Bands Produced when Hydrocarbon Com
pounds or Organic Compounds Containing Oxygen
were Sprayed into the Flame
When organic solvents were aspirated into the
flame, the emission intensity in general was increased, and scans
over the 2 0 0 -6 5 0 nm spectral region exhibited bands produced by excited organic fragments.
When solvents containing carbon, hydrogen, and/or oxygen atoms were aspirated into the flame, in addition to OH emis sion, the 390.0 nm C H , the 630.0 nm CH, and the Swan C2 Systems were observed (1 5 6, 192, I9 8). See Tables II and VI and Figs. 6 and 1 0 -b. Tabic II. Emission Bands Produced when Hydrocarbon Compounds or Or
ganic Compounds Containing Oxygen were Sprayed into the
Flame
wavelengths of band maxima, (nm)* emitting species
j>87 CH
3 8 9 CH
^31 CH
^68 C2
kjO C 2
kj2 C2
47U C2
513 • c2
516 C2
5^6 c2
550 c2
55[t- c2
558 c2
5 6k C2
^Wavelengths were mea.sured to + 3 nm «
c . Emission Bands Produced when Compounds Containing
Nlueogen were Sprayed into the Flame
In addition to emission from excited OH, CH, and 1 0 5 0 . 775 nm
Fig. 3. Emission Produced by Excited Water Molecules
in the Oxyhydrogen Flame C1I (Slit 0.23 mm)
kkO nm
CH (Slit 0.20 mm)
570 nm
C:. (Slit 0.13 mm) C'22 (Slit OJ+O mm)
Fig. 2. Emission Bands Produced by Excited CH and Co Fragments
Benzene was sprayed into the flame. Flame Height: 0.75 cm- C;> fragments , solvents containing nitrogen atoms produced emission bends between 200 and 270 nm, which were probably due to CN and/or
NO fragments (19^ > 198), bands belonging to the 336*0 Nil System (I9 8), bands belonging to the Violet CN System (156, I8 5, I9 8), and a band at bpO nm which was probably due to Nil (I9 8.). See Tables III and VI and Figs. 5> 10-d, and 1 3 . NH emission was produced by nitroethane as well as by amine solvents. Concentrated ammonium hydroxide also produced Nil emission.
Table III. Emission Bands Produced when Compounds Containing Nitro
gen were Sprayed into the Flame
wavelength of band maxima (nm)* species emitting
21b CN, NO
225 CN, NO
236 CN, NO
2^7 CN, NO
258 CN, NO
33 8 NH
337 NH
359 cn
385 cn
387 CN
bl6 CN
ltl8 CN 57
(Continuation of Table III)
wavelength of band maxima (nm)* species emitting
720 CN
722 CN
750 NH
•''Wavelengths were measured to + 3 nm.
d . Emission Bands Produced when Compounds Containing
Phosphorus were Sprayed into the Flame
In addition to OH, CH, and C2 emission, tributyl phosphate and triethyl phosphate produced bands belonging to the Y
System of PO (1 9 8), bands belonging to the 0 System of PO (I9 8), and a band at 370 nm which probably belongs to the 370.0 nm PH System and is possibly due to some emission from PO (I9 8). See Tables IV and
VI and Figs. 6, 7 and 10-e. Concentrated phosphoric acid and a 1 5^ aqueous solution of ammonium dihydrogen phosphate produced PO emis sion.
Table IV. Emission Bands Produced when Compounds Containing Phos
phorus were Sprayed into the Flame
wavelength of band maxima. (nm)* species emitting
230 PO y System
237 PO Y System
276 PO y System 38
(Continuation of Table IV)
• wavelength of band maxima (nm)* species emitting
253 PO Y System
325 PO 3 System
326 PO 3 System
327 PO 3 System
3^0 PH
*Wavelengths were measured to + 3 nm.
e . Emission Bands Produced.when Organic Compounds
Containing Sulfur were Sprayed into the Flame
In addition to OH, C H , and C2 emission, thio- phene and dimethyl sulfoxide produced CS bands (I9 8), bands belonging to the 323-7 nm SH System (1 9 8), and several very weak bands in the
3 0 0 -^ 5 0 nm region which indicate that other fragments containing sulfur such as SO, S2 , etc. were also produced in the flam§ (1 5 6,
1 9 8). See Tables V and VI and Figs. 8 and 10-f.
Table V. Emission Bands Produced when Organic Compounds Containing
Sulfur were Sprayed into the Flame
wavelength of band maxima (nm)* species emitting
258 CS (Continuation of Table V)
wavelength of band maxima (nm)* species emitting
260 CS
32k SH
328 SH
*Wavelengths were measured t0+3 nm.
f. Emission Bands Produced when Organic Compounds
Containing Chlorine were Sprayed into the Flame
In addition to OH, C H , and C2 emission, solvents containing chlorine produced a band at 2 5 8 nm which was probably due to CC1 (I9 8). See Figs. 9 and lh.
g . Emission Produced by Sodium Impurity
A strong emission at 590 nm was frequently ob served. It was attributed to sodium impurity (55>.19T)*
h . Emission Produced by Mei~cury in the Fluorescent
Lights in the Laboratory
Lines at 3 6U , ^0^+, ^ 36, and 5^7 nm, which appeared even when the region was scanned without the flame, were attributed to mercury emission from the fluorescent lights in the laboratory
(197). —I------1------1------j------1------}_ 2 2 0 2 h 0 2o 0 nm
Fig. 5 . Emission Bands Produced by Excited
CN and NO Fragments
Pyridine was sprayed into the flame. Flame height: 0.75 c^. •71
27 Q 2o0 nm
Fig. o. Emission Bands Produced by Excited PO Fragments
Triethyl Phosphate was sprayed into the flame. Flame height: 0.7" cm. I h i
_L
320 335 nm
Fig. 7* Emission Bands Produced by Excited PO Fragments
Triethyl phosphate was sprayed into the flame. Flame height: 0 .75 cm* 250 2'70 nm
Fig. 8. Emission Bands Produced by Excited CS Fragments
Thiophe'ne was sprayed into the flame. Flame height: O .7 5 cm
2 5 0 270
Fig. 9- Emission Produced by Excited CC1 Fragments
Chloroform was sprayed into the flame. Flame height: 0.75 cm Table VI. Emission Bands Produced by Oxyhydrogen Flames into which
Organic Compounds were Sprayed
wavelength of band maxima, (nm)* emitting species
211+ CN, NO
225 CN, NO
250 PO
236 CN, NO
237 PO
276 PO
277 CN, NO CM LT\ k ' n PO
258 CN, NO
258 CC1
258 CS
260 CS
262 OH
269 OH
283 OH
289 OH
295 OH
307 OH
309 OH
327 SH
325 PO
326 PO
327 PO 75
(Continuation of Table VI)
wavelength of band maxima (nm)* emitting species
328 SH
336 NH
337 NH
3I1-O PH
3*1-3 OH
378 OH
359 CN
3 67 Hg
385 CN
387 CN
387 CH
389 CH
7o7 Hg
716 CN
718 CN
720 CN
722 CN
731 CH
736 Hg
750 NH
768 C2
770 C2
772 c2
777 c2 b-6
(Continuation of Table VI)
wavelength of band maxima (nm)* emitting species
513 c2
516 c2
5)16 c2
5[i-7 1-1 g
550 c2
55^ C2
558 c2
5 6h c2
590 Na
930 H 20
970 h 2o
*Wavelengths were measured to + 3 nm.
2. Comparisons of Emission Spectra Produced by Different
Solvents
Emission scans over the 220-600 nm region were ob
tained for the flame alone and with several solvents6 at heights of 0 .7 5> 2 , and 3 cm above the tip of the burner in order to compare
spectra obtained from different samples under the same conditions and in order to compare spectra produced by the same sample at dif
ferent flame heights. See Figs. 10, 11, and 12.
6benzene, butyl alcohol, pyridine, tributyl phosphate, thiophene UT
Variations in the emission spectra obtained for dif ferent samples under the same conditions depend upon the rates at which the solvents are aspirated into the flames and upon the chemi cal and physical processes that occur in the flames.
The turbulent diffusion flame produced by the Beckman
total consumption burner is discussed on page 26 of this thesis.
Aspiration rates for the different solvents are shown in Table VII.
Table VII. Solvent Aspiration Rates
gas flow rates: oxygen (aspirating) 3*5 1/min. hydrogen 10.0 1/min.
Solvent ml aspirated into the flame per min.
benzene 1.3
cyclohexane 1.1
distilled water 1.0
butyl alcohol 0.5
amyl acetate 1.0
methyl isobutyl ketone l.k
anisole 0 .9
acetic acid 0 . 7
butylamine 1 .5
pyridine 1.0
nitroethane 1.2
tributyl phosphate 0.3
triethyl phosphate 0 .6
thiophene 1.3 48
(Continuation of Table VII)
Solvent ml aspirated into the flame per min.
dimethyl sulfoxide 0.5
chloroform 1.1
butyl chloride 1.7
The size, shape, and structure of the flames varied with the different solvents. At flow rates of 3*5 1/min. of oxygen and 10 1/min. of hydrogen, the flame by itself was visible to a height of 6 cm and had a maximum diameter of about 1 cm, approxi mately 4- cm above the burner. When relatively non-combustible sol vents such as ethanol or dimethyl sulfoxide were aspirated into the flame the size of the flame was increased slightly. For very com bustible solvents such as benzene or pyridine the flame became visible to a height of 8 cm and had a maximum diameter of about 2 cm at a height of ^-6 cm above the tip of the burner. For all solvents the blue cone generally extended from 0.1 cm above the tip of the burner, where the flame began, to 1 .5- 2 cm above the burner.
The relative intensities of the bands produced by ex cited organic fragments were highest in the spectra from the blue reaction zone. See Fig. 10. OH emission was most intense 3 cm above the burner. See Fig. 12. PO bands were relatively intense at flame heights of 2 and 3 c m 5 as shown in Figs. 11 and 12.
In addition to bands, background emission was observed over wide spectral regions, especially at a flame height of 3 cm, and 1^9
in particular for the solvents containing phosphorus and sulfur.
See Figs. 12-e and 12-f. Compounds containing phosphorus produce a strong continuum in flames in the visible.region that is due to emission by PO (lH, 6 l , I5I , I8 7). The high background emission produced by dimethyl sulfoxide and thiophene can be attributed to the presence of S02 , which produces a strong continuous emission and also a violet or blue color in the flame (lU). The dimethyl sulfoxide flame was violet, and the thiophene flame was blue.
In Fig. 13 are shown emission spectra obtained from pyridine and nitroethane samples under identical conditions at a flame height of 0.75 cm- 1° Fig. 17 are shown emission spectra ob tained from chloroform and butyl chloride.under identical conditions
0.75 cm above the burner. NH emission from nitroethane and C2 emis sion from chloroform are evidence of the involved chemical pro cesses that occur in the reaction zone of the flame (12). Hydrogen: 10 1/min.
OH
OH
Hg
220 300 4oo 600 nm vn Fig. 10-a. Emission Spectrum of the Oxyhvdrogen Flame at a Height: of 0.73 cm« O OH
CH
H g
OH
CH
220 600 nm
V" Fig. 10-b. Flame Emission Spectrum of Benzene at a Height of 0 .7b cm- Oxygen: 3*5 1/min. Hydrogen: 10 l/min.
OH
OH CH
220 300 500 600 nm
\_n Fig. 10-c. Flame Emission Spectrum of Butyl Alcohol at a Height of 0.72 cm. ro 0 / i .xy g e n : gen: 10 l/min.Ox
OH CN
CH
CN
OH NH CN
220 500 600 nm
V>J Fig. 10-d. Flame Emission Spectrum of Pyridine at a Height of 0.75 cm. Slit 0.30 mm. Gain 7-5 •
Oxygen: 3-5 1/min. Hydrogen: 10 1/min.
OH
Na
PO
OH C1I
PO PH
220 300 koo 5 00 600 nm
vn Fig. 10-e. Flame Emission Spectrum of Tributyl Phosphate at a Height of 0 .71? cm. Oxygen: 3-5 1/min. Hydrogen: 10 1/min.
OH
CH
OH
CS Na
220 300 500 600 nm
Fig. 10-f. Flame Emission Spectrum of Thiophene at a Height of 0.73 cm. cc OH
Oxygen: 3-5 1/min. Hydrogen: 1 /min.
OH
Hg
OH OH
— I- 220 600300
Fig. 11-a. Emission Spectrum of the Oxyhydrogen Flame at a Height of 2 era. OH Slit 0.30 mm. Gain 7-5•
Oxygen: 3-5 1/min. Hydrogen: 10 l/min.
CH
OH
H ------1 — ------1------t------1- 220 300 700 5 0 0 60 0 nm
V J i Fig. 11-b. Flame Emission Spectrum of Benzene at a Height of 2 cm. — 3 OH
Oxygen: 3-5 l/min. Hydrogen: 10 1/rain.
OH
Na
OH OH CH
220 300 vn Fig. 11-c. Flame Emission Spectrum of Butyl Alcohol at a Height of 2 cm. Co OH Slit O.JO mm. Gain 7-5«
Oxygen: 3*5 l/min. Hydrogen: 10 1/min.
CN
Na
NH CH CN OH
220 300 hoo 500 600 nm
\J1 Fig. 11-d. Flame. Emission Spectrum of Pyridine at a Height of 2 cm. vo Na OH Slit 0.30 mm. Gain J
Oxygen: 3 .5 1/min. Hydrogen: 10 l/min.
PO
OH
PH
OH
PO
220 300 500 600 nm
Cn C Fig. 11-e. Flame Emission Spectrum of Tributyl Phosphate at a Height of 2 cm. Oxygen: 3-5 1/min. Hydrogen: 10 l/rain.
Na
CH Hg
3 0 0 bOO 500 600 nm220
Fig. 11-f. Flame Emission Spectrum of Thiophene at a Height of 2 cm. OH No flame.
OR
Oxygen: J.5 1/min. Hydrogen: 10 l/min.
OH OH
H g Na
220 500 600 nm
o\ Fig. 12-a. Emission Speefmm of the Oxyhydrogen Flame at a Height of 5 ro OH
Slit 0.30 nun. Gain 7-5 •
Oxygen: 3*5 1/min. Hydrogen: 10 l/min.
OH
CH Hg
Na
H ------1------— ------1------1------1--- 220 300 U00 500 6 0 0 nm
ON Fig, 12-b. Flame Emission Spectrum of Benzene at a Height of 7 cm« ^ OH Oil
Oxygen: 3-5 l/min. Hydrogen: 10 l/min. Na
OH
OH
H g
300 bOO 500 600 ran
O n _ p r Fig. 12-c. Flame Emission Spectrum of Butyl Alcohol at a Height of 3 cm- OH Oil
Oxygen: 3*5 l/min. Hydrogen: 10 l/min.
Na
OH
OH
CN
CH
220 300 600 nm
O-N Fig. 12-d. Flame Emission Spectrum of Pvridine at a Height of y cm. VJ1 u /I/i/7’ '
Slit 0.30 mm. Gain 7«5>
Oxygen: 3-5 l/min. Hydrogen: 10 l/min,
220 300 ilOO 500 600 nm c\ Fig. 12-e. Flame Emission Spectrum of Tributyl Phosphate at a Height of 3 c Slit O.JO mm. Gain 7-5 •
Oxygen: 3*5 l/min. Hydrogen: 10 l/min.
Na
220 300 1*00 500 600 nm
Fig. 12-f. Flame Emission Spectrum of Thiophene at a Height of 3 V./1 CN Fig. 13 a Flame-a.Emission Spectrum of Pyridine 1*00 CN CH Nil Oxygen: lt .y m Gain mm. O.gy Slit Height 0 O nm vOO : n e g o r d y H -tOl/min. CO 00 Height 0. 7
Cll Oxygen: 3-5 l/min. Hydrogen: 10 l/min.
CN
NH
Oil CN
100. pOJ nm
Fig. IjJ-b. Flame Emission Spectrum of Nitroctrhano Height O.Jy cm.
Slit 0 . '+0 m m . Ga in 7
O x y g e n : ; l/min. Hydrogen: 10 1/nin.
Hg
CH
Fig. Ih-a. Flame Emission Spectrum of Chloroform Height 0 . 75 cm.
Ctl Oxygen : 3 • 3 1 /rii-n • Hydrogen : 2-0 l/min.
IH'11 O
CH
Hg
300 nm
Fig. lli-b. Flame Emission Spectrum of Butyl Chloride 72
5• Emission Profiles for Fragments
Flame profiles were obtained at several wavelengths by measuring the intensity of emission at selected flame heights. The profiles are shown in Figs. 15 through 2 h . In Figs. 1 6 - the signal from the flame alone was subtracted from the total emission intensity of the flame plus the sample, and the difference was plotted as a function of flame height. A flame height of zero corresponds to the tip of the burner.
At 309 nm the emission was most intense between 2.0 and h.O cm above the tip of the burner. This is shown in Fig. 15 .
Emission at this wavelength was from the excited OH fragment.
The profiles at 13 1 nm (emission from the excited CH fragment), boQ nm (C2 fragment), ~$Q6 (CN), and 336 (n h ), are similar, as shown in Figs. 16 through 1 9 . Maximum emission occurred between
0 .5 and 2 cm above the burner, which was within the reaction zone of the flame.
The emission profiles for OH, CH, C2 , CN, and NH, shown in Figs. 15 through 1 9 , agree with the spectra obtained at flame heights of 0.75> 2, and 3 c m > as shown in Figs. 10, 11 and 12.
They are also in general agreement with reports in the literature,
(150, 176).
Profiles for phosphate samples at 2U-6 nm show maximum emission intensity between 0 .5 and 2 cm above the tip of the burner, but emission is intense above the reaction zone as well. See Fig.
20. Profiles at 327 am show maximum emission intensity between 1.5 and 3 .5 cm above the burner. See Fig. 21. The profiles for tri butyl phosphate and triethyl phosphate agree with the emission spectra I i 73
obtained at flame heights of 0.75> 2, and 3 cm, which show relatively
intense PO bands above the reaction zone of the flame and high back
ground emission from above the reaction zone at 3 2 7 nm. See Figs.
10-e, 11-e, and 12-e.
The emission profile for thiophene at 259 nm shows
maximum emission intensity from the reaction zone and intense emission
higher in the flame as well. See Fig. 22. The profile at 328 nm
for the thiophene and dimethyl sulfoxide samples shows maximum emis
sion between 1.5 and k.5 cm above the burner. See Fig. 23- The emis
sion spectra for these solvents, shown in Figs. 10-f, 11-f, and 12-f,
exhibit a band produced by the excited CS fragment at 259 nm and a
band at 328 nm produced by the SH fragment. The CS band is most
pronounced at a height of O .7 5 cm. See Fig. 10-f. There is intense
background emission from 2 and 3 cm above the burner at 2 5 9 nm and
at 328 nm, as shown in Figs. 11-f and 12-f.
Background emission at 327 nm from solvents contain
ing phosphorus and at 3 2 8 nm from solvents containing sulfur may
contribute significantly to the intensity measurements shown in
Figs. 21 and 23*
The profile for chloroform at 258 nm shows that max
imum emission intensity from the CC1 fragment is from the reaction
zone of the flame. See Fig. 2b.
I 7^
FI ci me Height (cm)
on
w'“ c 10 60 100
Relative Intensity
F ig . 1 5 . Flame Em is .si on Profile at yOQ n m .
No solvent. Slit 0.2‘j mm. Gain 6.1
F 1 a me Height (cm)
CH
20 60 100 Relative Intensity
Fig. 16. Flame Emission Profile at h'-'yl nm. Benzene was sprayed into the flame. Slit 0.25mm. Gain 6 .8 . 73
F 1 a me Height (cm)
J- 20 oO J-00
Relative Intensity
Fig. 17. Flame Emission Profile at 7 6 8 n m .
Eenzene was sprayed into the flame.
Slit 0.25 mm. Gain 7-3
Florae Height (cm)
CN
-r
p
0 20 GO 1 0 0
Relative Intensity
Fig. lb. Flame Emission Profile at 736 nm. Pyridine was sprayed into the flame. Slit 0.20 mm. Gain 6.8 TC
F1 a me Height; (cm)
Nil
20 60 100 Relative Intensity
Fig. 19. Flame Emission Profile at y>6 n m .
Pyridine was sprayed into the flame.
Slit 0.25 mm. Gain 7*0
F 1 a me Height (cm)
P0 ■Q> °
lr
2
0 20 60
Relative Intensity
Fig. 20. Flame Emission Profile at 2-itO n m .
Tributylx phosphate and triethyl*'* phosphate were sprayed into the Ilame. Slit 0.2g mm. Gain 7*7- YY
F 1 nmo Height (era)
PO
4i
0 20 00 100
Relative Intensity
Fig. 21. Flarae Emission. Profile at Q2j' nra.
Tributyl' phosphate and triethyl** phosphate were sprayed into the f 1 a rae .
Slit 0.2p mm. Gain 0.2
Flame Height (cm
C S b nd S 0 o
20 00 100
Relative Intensity
Fig. 22. Flame. Emission Profile at 2S° nm. Thiophene was sprayed into the flame. Slit 0.2g. Gain 7.8 78
F 1 a me Height (cm)
SH and SO
k "
2 - -
20 60 100
Relative Intensity
Fig, 23. Flame Emission Profile at 328 nm.
Dimethyl sulfoxide* and thiophene** were sprayed into the flame.
Slit 0.25 nm. Gain 6 .9*
Flame Height (cm)
CC 1
2
0 20 60 100 Relative Intensity
Fig. 2k. Flame Emission Profile at 238 nm.
Chloroform was sprayed into the flame.
Slit 0.55 nm. Gain T-9- 79
7. Sensitivity Estimates for Emission Bands Produced by
Excited NH and CH Fragments
It was found that mixtures of two solvents produced
emission bands characteristic of each . Flame analyses for nonmetals
include measurements of emission produced by excited flame fragments
such as CH, PO, etc. This is discussed on page 20 of this thesis.
We obtained estimates of sensitivity for our experimental conditions
for pyridine-ethanol and ethanol-water solutions at a flame height of
0.75 cm» Oxygen and hydrogen flow rates were 3*5 and 10 l/min., respectively.
For pyridine-ethanol solutions at 35^ nm, where emis
sion from the N11 fragment was observed, a concentration of > 2$, pyri dine was required to produce a signal significantly greater than
that produced by ethanol. For ethanol-water solutions at 731 nm, where emission from the CH fragment was observed, a concentration
°f ^ 5
Gilbert (I7 5) reported that approximately 0.01$, of an alcohol could be detected by CH and C2 emission in a hydrogen flame.
McCrea and Light (I5 0 ) observed linear responses of CH and C2 emis sion intensities with the hydrocarbon concentrations of methanol solutions.
5. Effects of Varying the Hydrogen to Oxygen Ratio in
the Flame on the Emission Spectra
Emission spectra were obtained in the 220-600 nm re gion for the flame and for the flame into which benzene, butyl alco hol, pyridine, tributyl phosphate, and dimethyl sulfoxide samples were 80
aspirated at distances of 0 . 7 5 j 2 , and 3 cm above the burner and hy drogen to oxygen ratios of 5/3-5 and !/3.5 (l/min.). See Figs. 25 and 2 6. .These spectra were compared with the spectra obtained at a hydrogen to oxygen ratio of 10/3-5 (l/min.) shown in Figs. 10, 11, and 1 2 .
The sizes of the flames were decreased drastically as the hydrogen to oxygen ratio was decreased. At a rate of 5 l/min. of hydrogen the flame by itself was approximately 3-5 cm high. The butyl alcohol and dimethyl sulfoxide samples increased the size of the flame slightly. The pyridine and benzene samples increased the visible limits of the flame to 6 cm above the burner and a diameter of about 1.5 cm, approximately A.5 cm above the burner. At a flow rate of 1 l/min. of hydrogen when benzene or pyridine was aspirated into the flame the visible limits of the flame were increased from
1 to 4 cm in height and to a diameter of about 1 cm, approximately
3 cm above the burner.
The differences in the spectra obtained at different hydrogen to oxygen ratios reflected the different sizes of the flames
involved. Emission from the OH fragment in the flame alone was most
intense at 3 cm above the burner for a hydrogen flow rate of 1 0
l/min., at 2 cm above the burner for a flow rate of 5 l/min. of hydrogen, and at 0 .7 5 cm above the burner for a. flow rate of 1 l/min.
of hydrogen. See Figs. 12-a and 25“b. At hydrogen flow rates of 5
and 1 l/min,, when benzene was aspirated into the flame, the emis
sion from the OH fragment was most intense at 3 and 2 cm above the
burner, respectively, reflecting the increased size of the flame when benzene was burned. See Fig. 26. fjl
OH
500 yj Q nm
F i g. 'c’rj> - a . Em t as i on Spectrum of Lhc Oxyhydrogen Flame at a Hydrogen
to OxyL’on Ratio of r;i / i . 0 and a Height of O . J ‘5 c m .
No solvent. Slit O.'jO mm. Gain 7-
Oxygen: J.y l/min. Hydrogen: 5 l/min. 82
on
OH
OH
Fig. 25-b. Emission Spectrum of the Oxyhydrogcn Flame at a Hydrogen
to Oxygen Ratio of S/o.o and a Knight of P cm.
No solvent. Slit 0.30 mm. Gain rf.
Oxygen: 3*5 l/min. Hydrogen: 3 l/min. y'jG nm
Fig. 23 - c, Emission Spectrum of f.ho Oxyhydrogcn Flame at a Hydrogen
to Oxygen Ratio of 3/3.3 and a Height of a cm.
No solvent. Slit 0.30 mm. Gain 7.
Oxygen: 3.5 l/min. Hydrogen: 5 l/min. Slit O.JO mm. Gain J,
Oxygen: 3-5 l/min. Hydrogen: 5 l/min.
CH OH
Cp
CH OH
^ a a v / ^
2 2 0 300 1 0 0 5 0 0 6 0 0 nm
Fig. 26-a. Flame Emission Spectrum of Benzene at a Hydrogen to Oxygen Ratio of 5/3-5 and a Height of 0.7? cm. OH
Oxygen: 3*5 l/min. Hydrogen: 5 l/min.
OH
CH OH
OH
Na
220 Uoo 600500 nm
co Fig. 26-b. Flame Emission Spectrum of Benzene at a Hydrogen to Oxygen Ratio of 5/3-3 and a Height of 2 cm. VJ1 OH
Oxygen: 3»5 l/min. Hydrogen: 5 l/min.
OH
OH
CH Hg OH
Na
220 300 h o o 500 6 00 nm
cn Fig. 26-c. Flame Emission Spectrum of Benzene at a Hydrogen to Oxygen Ratio of 3/3•5 and a Height of 3 cm. 87
For hydrogen to oxygen ratios of 10/3-5, 5/3-5> a^d
1 /3 - 5 (l/min.), emission from organic fragments was most intense at a flame height of 0.75 cm> which was within the reaction zone. Emis sion from the excited P0 fragment was appreciable at 2 and 3 cm a- bove the burner at flow rates of 5 l/min. and 1 0 l/min. of hydrogen.
6 . Effects of Aspirating with Hydrogen instead of Oxygen
on the Emission Spectra
Generally when total consumption burners are used the sample solution is aspirated into the flame with oxygen. This pro vides an oxidizing environment for the sample constituents. Aspira tion with hydrogen instead of oxygen should produce a more reducing atmosphere for the sample (1 0 1 ).
The effect of aspirating with hydrogen on the emis sion spectra from several solvents was studied by switching the hy drogen and oxygen gas lines at the burner. Emission spectra were obtained for the flame and for the flame into which benzene, butyl alcohol, pyridine, tributyl phosphate, and dimethyl sulfoxide samples were aspirated with hydrogen at flame heights of 0 .7 5j 2 , and 3 Cm-
The flame emission spectra of pyridine are shown in Fig. 2J . The hydrogen flow rate was 1 0 l/min. and the oxygen flow rate was 3 -5 l/min. The rates at which the samples were aspirated into the flame were relatively low: benzene approximately 0.4 ml/min., pyridine approximately 0 . 2 ml/min. and butyl alcohol, tributyl phosphate, and dimethyl sulfoxide samples: approximately 0 . 1 ml/min.
The flame was visibly 11 cm high with a diameter of about 1-5 cm at a flame height of 8-9 cm. Benzene, pyridine, butyl alcohol, and dimethyl sulfoxide samples only slightly increased the rJr > (j6
visible size of the flame because of the relatively small amount of sample that was aspirated into the flame for these solvents. The tributyl phosphate sample increased the visible limits to about 1 2 cm in height and to a diameter of about 3 cm, approximately 9 cm above the burner. This apparent increase in the size of the flame for the phosphate sample may be attributable to the bright yellow color that phosphate samples impart to the flame.
The spectra showed that emission from the OH fragment was most intense at 3 cm above the burner, and that emission from organic fragments was most intense at 0 .7 5 cm above the burner, as illustrated in Fig. 27. Emission from the excited PO fragment was intense at flame heights of 2 a.nd 3 cm. No marked differences were observed in (1 ) the spectra obtained from flames in which hydrogen was the aspirating gas and (2 ) spectra from flames in which oxygen aspirated the samples into the flame, indicating that the molecular species produced in both flames were the same. See Figs. 10-d, 11-d,
1 2 -d, and 2 7-
B. ABSORPTION SPECTRA
1. Wavelengths of Band Maxima and Identification of the
Species Absorbing
Absorption spectra, were obtained in the 200-620 nm region using hydrogen and tungsten lamps as sources of continuous emission.
Difficulties involved in obtaining absorption spectra, of radicals in flames have been mentioned. In order to obtain de tailed band spectra in this investigation, the size of the beam from the lamps was decreased by placing an aperture with a diameter of Slit O.JO mm. Gain 7-5-
OH CN Oxygen: 3*5 l/min.
Hydrogen (aspirating) 10 l/min. CH
CN
OH NH
CN
OH
NH Na
220 ^0 0300 500 600 nm
Fig. 27-a. Flame Emission Spectrum of Pyridine at a Height of 0.73 cm with Hydrogen Aspiration. OH Oxygen: 3-5 l/min.
Hydrogen (aspirating) 10 l/min.
OH
CN
NH CH
OH
CN
CN NH
220 300 50 0 600 nm \c o Fig. 27-b. Flame Emission Spectrum of Pyridine at a Height of 2 cm with Hydrogen Aspiration. OH OH Oxygen: 3-5 l/min.
Hydrogen (aspirating) 10 l/min.
Na
CN
NH 011
OH
220 300 500 600 nm
vo Fig. 27-c. Flame Emission Spectrum of Pyridine at a Height of 3 cm with Hydrogen Aspiration. H 92
0 .1 -0 . 6 cm between the lamp and the lens focusing the beam in the flame, as illustrated in Fig. 2. Figs. 23 and 33“d show absorption spectra, obtained for the pyridine sample in the 2 0 0 -3 5 0 nm region at a flame height of 0.75 cm* The spectrum shown in Fig. 28 was obtain ed with no aperture. The diameter of the beam from the hydrogen lamp was approximately 0.7 cm directly above the burner. No absorption bands were recorded. The absorption bands shown in Fig. 33~d were obtained by using the aperture to decrease the diameter of the beam to 0.1 cm in the flame. The same effect was observed for the tung sten lamp. These effects can be explained by considering the rela tively small region of the flame that absorbs. When the size of the light beam is not decreased only a small part of the source energy passes through the absorbing region of the flame, and a relatively small difference in signals is recorded. On the other hand when the source beam is concentrated in the absorbing region of the flame a relatively large difference in signals is recorded, as shown in Fig. yy-d. A similar effect is described by Rann and Hambly (108). They placed an aperture between the flame and the lens leading to the monochromator. The prominent absorption bands that were observed are listed in Tables VIII-XIII according to wavelength of band max ima and absorbing species.
a. Absorption Bands Produced by the Oxyhydrogen
Flame
The 306.h nm OH System was observed in the ab sorption spectrum of the oxyhydrogen flame (1 9 8). See Tables VIII and XIII and Figs. 33“b and 3^"a - No absorption bands observed. Height 0.7b cm.
Oxygen: 3-5 l/min. Hydrogen: 10. l/min.
200 250 300 350 nm \o 'oj Fig. 28. FI ame Absorption Spectrum of Pyridine with Source Beam Diameter 0.7 cm. 99
Table VIII. Absorption Bands Produced by the Oxyhydrogen Flame
wavelength of band maxima (nm)* species absorbing
2 6 2 OH
269 011
2 8 2 OH
289 011
307 OH
309 OH
3 1 2 OH
315 OH
319 OH
393 OH
398 OH
^Wavelengths were measured to + 3 nm.
b . Absorption Bands Produced when Hydrocarbons or
Organic Compounds Containing Oxygen were Sprayed
into the Flame
When solvents containing carbon, hydrogen, and/or oxygen atoms were aspirated into the flame absorption bands of the
390*0 nm CH, 930.0 nm C H , and Swan C2 Systems were produced, (29,
107, 192, 193). See Tables IX and XIII and Figs. 29, 3 8-b, and 3 8-c.
Absorption spectra for C2 , CH , and C3 have been reported by Fassel et. al. (107, 192), and by Jessen and Gaydon (24). 3So 393 nm ^60
Fig. 29. Absorption Rands Produced by CII and Co Fragments
Benzene was Sprayed into the flame. Flame height: 0.75 cm- 9 6
Tabic IX. Absorption Bands Produced when Hydrocarbons or Organic
Compounds Containing Oxygen were Sprayed into the Flame
wavelength of band maxima (nm)* species absorbing
587 CH
989 CH
791 CH
k'j>J CH
^68 c2
870 c2
872 C2
87U c2
510 c2
519 C2
516 c2
550 c2
55^ c2
c2
5 6k c2
KWa.velengths were measured to + 9 nm«
c . Absorption bands Produced when Compounds Con
taining Nitrogen were Sprayed into the Flame
In addition to OH, CH, and C2 absorption bands, 97
when solvents containing nitrogen atoms were aspirated into the flame,
the 999.0 nm Nil System, the Violet CN System (some absorption from CH
was possibly observed in this region also), and a band at 4p0 nm, which was probably due to NH , were observed in the absorption spectra
(107, 192,198). See Tables X and XIII and.Figs. 30, 31, 33-1, and
3 8-d.Absorption spectra of the CNfragment have been reported by
Fassel e_t. _al_. (107, 192).
Table X. Absorption bands Produced when Compounds Containing Nitro
gen were Sprayed into the Flame
wavelength of band maxima, (nm)* species absorbing
336 NH
337 NH
359 CN
385 CN
386 CN
387 CN
388 CN
4-15 CN
417 CN
418 CN
420 CN
422 CN
450 NH
•^Wavelengths were measured to + 3 nm. 96
NH
CN — ! 1 1- 990 950 9T0
Fig. 90• Absorption Bands Produced by NH and CN Fragments
Pyridine was sprayed into the flame. Flame height: 0.75 cm- 375 395
Fig. 51. Absorption Bands Produced by CN Fragments
Pyridine was sprayed into the flame. Flame height: 0.7' cm. 100
d, Absorption Bands Produced when Compounds Con
taining Phosphorus were Sprayed into the Flame
When, tributyl and triethyl phosphate samples were aspirated into the flame, in addition to OH, CH, and C2 absorption bands, the 3 and y Systems of P 0 , and a. band at ^,k0 nm, which was the
3^0.0 nm PH System and possibly some absorption by P0, were observed
(198). See Tables XI and XIII and Figs. 32 and 3 3 -f.
Table XI. Absorption bands Produced when Compounds Containing,
Phosphorus were spx~ayed into the Flame
wavelength of band maxima (nm)* species absorbing
237 PO Y System
2 k o P0 Y System
253 PO Y Sys tern
325 PO 3 Sys tern
326 PO 3 System
327 PO 3 Sys tern
310 PH
•x-Wavelengths were measured to + 3 n m *
e . Absorption Bands Produced when Organic Compounds
Containing Sulfur were Sprayed into the Flame
In addition to OH, CH, and C2 absorption, samples 101
l l
!i!i f
+ 320 330 3*4-0 nm 235 225 255 nm
Fig. 32. Absorption Bands Produced by PO Fragments.
Triethyl phosphate was sprayed into the flame. Flame height: 0.75 cm. 102
containing sulfur atoms produced absorption bands due to the CS frag ment and a band at jp23 nm, which was part of .the 323*7 nm SII System
(and possibly some absorption by the SO fragment), (1 9 8). See Tables
XII and XIII and Fig. 33"S*
Table XII „ Absorption Bands Produced when Organic Compounds Contain-
ing Sulfur were Sprayed into the Flame
wavelength of band maxima (nm)* species absorbina
2 5 8 CS
2o0 CS
328 SH
■^Wavelengths were measured to + 3 nm-
f . Absorption Bands Produced when Organic Compounds
Containing Chlorine were Sprayed into the Flame
Solvents containing chlorine produced an ab
sorption band at 2 5 8 nm which was attributed to the CC1 radical (I9 8).
g . Absorption Produced by Sodium Impurity
Absorption at 590 nm was attributed to absorp
tion by sodium impurity (I9 7)-
2. Comparisons of Absorption Spectra Produced by
Different Solvents
Absorption spectra were obtained for flames into which 105
Table,XXIX. Absorption Bands Produced by Oxyhydrogen Flames into
which Organic Compounds were Sprayed
wavelength of band maxima (nm)* species absorbing
257 PO
2 U6 PO
255 PO
2 5 8 CCl CO CV] LT\ CS
2 60 CS
2 6 2 OH
269 OH
2 8 2 OH
28k OH
507 OH
509 OH
512 OH
515 OH
5 19 OH
525 PO
526 PO
527 PO
5 2 8 SH
556 NH
557 NH
51-0 PH
5^5 OH 104
(Continuation of Table XIIl)
wavelength of band maxima (nm)* species absorbing
343 OH
359 CN
385 CN
386 CN
387 CN
387 CH
388 CN
389 CH
U-15 CN
417 CN
1+18 CN
420 CN
422 CN
431 CH
437 CH
450 NH
468 C2 470 c2
472 c2
474 c2 510 c2 513 c2
516 c2 550 c2 105
(Continuation of Table XIIl)
wavelength of band maxima (nm)* species absorbing
55^ C2
558 c2
56^ C2
590 Na
*Wavelengths were measured to + 3 nm*
several solvents7 were aspirated, at flame heights of 0.75 > 2, and
5 cm, in order to compare spectra obtained from different compounds
under the same conditions and also in order to compare spectra ob
tained from the same solvent at different flame heights. The dia
meter of the beam from the hydrogen or tungsten lamp as it passed
through the flame was 0.1-0.2 cm.
Emission scans detected from the unmodulated flames were also obtained by blocking the light beam from the lamp and re
cording the emission signal over the wavelength range. Problems with noise produced by flame emission have been mentioned with re
spect to atomic absorption and atomic fluorescence measurements. At
sensitive instrument settings, i.e. wide slits and high gains, appre
ciable flame emission is detected, as shown in Fig. 38-g. There is
a possibility of reflection from the face of the lamp and subsequent
modulation in some instances (8l).
7benzene, butyl alcohol, pyridine, tributyl phosphate, thio- phene, dimethyl sulfoxide 106
Absorption scans were obtained for whole organic sol
vent molecules by aspirating the sample into the light path with no
flame burning. In these instances the oxygen flow rate was 3-5 l/min.
and the hydrogen flow rate was zero.
Fig* 33 shows absorption scans in the 2 0 0 -3 5 0 nm re
gion obtained with a hydrogen lamp at a flame height of 0.75 cm*
In addition to the absorption bands attributed to
fragments, absorption over wide spectral regions was observed when
pyridine and thiophene samples were aspirated into the flame, as
shown in Figs. 33“^ and 33“g- There was strong absorption in the
same regions for the pyridine spray (230-280 nm) and for the thio
phene spray (200-250 nm), as shown in Figs. 33”e and 33"h- Absorp
tion by the pyridine and thiophene solvent molecules agrees with the
Sadtler uv spectra, as shown in Figs. 36 and 37 (207). Absorption
in these wavelength regions observed when pyridine and thiophene were
sprayed into the flame were attributed to whole unburned solvent mol ecules. No significant absorption was observed for benzene, butyl
alcohol, tributyl phosphate, or dimethyl sulfoxide molecules.
Fig. 3U shows absorption spectra obtained at a flame height of 2 cm.
The OH absorption bands are more intense at 2 cm than at 0.75 cm above the burner; however the other fragment absorption
bands are less intense.
There was less absorption by pyridine and thiophene molecules in the flame at 2 cm, presumably because more of the sol vent had been burned at this height. There was marked absorption by
the pyridine and thiophene sprays, however, as shown in Fig. jk-e. 107
Absorption over wide spectral regions occurred when
samples containing phosphorus or sulfur were aspirated into the
flame, as shown in Figs. ph-c and yh-d. Emission was detected from
the excited PO fragment between '-j2h and 333 nm as shown in Fig. 3^“c -
Fig. 35 shows absorption spectra obtained at a flame
height of 3 cm-
No fragment absorption bands were observed except
those produced by OH.
No absorption was observed at a flame height of 3 cm
for the pyridine molecule in the flame, and only slight absorption was observed for thiophene in the flame, although the sprays absorbed
strongly in the 230-280 and 200-250 nm regions, respectively.
Absorption over wide spectral regions was produced
in the flame by samples containing phosphorus or sulfur. No Flame
Slit 0.40 mm. Gain 6.3-
200 3 00 nm 108
Fig. 33-a. Hydrogen Lamp No Solvent.
Slit 0.^0 mm. Ga in
Oxygen: 3-5 l/min. Hydrogen: 10 l/min.
200 250 300
Fig. 33"b. Absorption Spectrum of the Oxyhydrogen Flame at a Height of 0.73 cm. Slit O A O mm. Gain 6 .3 .
Oxygen: 3-5 l/min. Hydrogen: 10 l/min.
OH
200 300 110 Slit O.UO mm. Gain 6.3* V w
Oxygen: 3-5 l/min. Hydrogen: 10 l/min.
OH
NH 111 200 250 300
Fig. 33-d. Flame Absorption Spectrum of Pyridine at a Height of 0.73 Cm- No flame. Slit O.hO mm. Gain 6.3
Oxygen: 3*5 l/min.
250 300200 112 Fig. 33_e* Absorption Spectrum of Pyridine at a Height of 0.73 cm. Slit O.ijO mm. Gain 6 .3 .
Oxygen: 3 .5 l/min. Hydrogen: 10 l/min.
k Ji
OH PO PH
200 3!;0 nm
V.N' Fig. 33"f. Flame Absorption Spectrum of Tributyl Phosphate at a Height of O .73 cm. Slit O.UO mm. Gain 6.3-
Oxygen: 3*5 l/min. Hydrogen: 10 l/min.
CS
OH
200 250 300 330
Fig. 33“§• Flame Absorption Spectrum of Thiophene at a Height of 0.73 cm. No flame. Slit OjiO. Gain 6 .J.
Oxygen: 3-5 l/min.
200 250 300 H H v/i Fig. 33"h. Absorption Spectrum of Thiophene at a Height of 0.73 cm. OH
No Solvent.
Slit 0.^0 mm. Gain 6.3.
Oxygen: 3 .5 l/min. Hydrogen: 10 l/min. OH
OH
200 250 300
Fig. 3^-a. Absorption Spectrum of the Oxyhydrogen Flame at a Height of 2 cm. OH
Slit 0 .hO mm. Gain
NH Oxygen: 3 .5 l/min. Hydrogen: 10 l/min.
OH
200 250 30O
Fig. 3^-b. Flame Absorption Spectrum of Pyridine at a Height of 2 cm. PO
OH
Slit O.UO mm. Gain 6.3.
Oxygen: 3*5 l/min. Hydrogen: 10 l/min.
OH
200
Fig. 3^-c. Flame Absorption Spectrum of Tributyl Phosphate at a Flame Height of 2 cm. OH
Slit O.iO mm. Gain 6.3•
Oxygen: 3 .5 l/min. Hydrogen: 10 l/min.
200 300
Fig. 3^--d. Flame Absorption Spectrum o£ Thiophene at a Height of 2 cm. No flame. Slit O.UO E2 . Gain £.
Oxygen: 3-5 1/niin.
200 250 300 0 2 1
Fig. Jh-e. Absorption Spectrum of Thiophene at a Height of 2 cm. Slit 0.-0 mm. Gain 6.J.
Oxygen: l/min. Hydrogen: 10 1/'
OH
OH
200 1 2 1
Fig. 35-a. Flame Absorption Spectrum of Pyridine at a Height of 3 Slit O.J Gain 6 .
Oxygen: 3-5 l/min. Hydrogen: 10 l/min.
OH
Oil
200 300 122
Fig. 35-b. Flame Absorption Spectrum of Tributyl Phosphate at a Height of 3 cm. Slit 0. h 0 m m . Ga in 6 .3 ■
Oxygen: 3-5 l/min. Hydrogen: 10 l/min.
330 nm
Fig. 35-c. Flame Absorption Spectrum o£ Thiophene at a Height of 3 era. Absorbance
o.o --
0 . 5 "
1 .0 -
200 2 20 240 v_0 nm
Fig. . Absorption Spectrunv' o£ Pyridine
■*Sadtler uv 9 (2 0 '[) Absorbance l . O r
0 .0-- 200 220 260 260 500 nm
M Fig. 57- Absorption Spectrim.Oof Thiophene ro
-Sadtler nv 63 (207) 126
Fig. 56 shows absorption scans obtained in the 350-
6 2 0 nm region at a flame height of 0.75 cm with the tungsten lamp.
No absorption was observed for the flame by itself or for the solvent sprays. Marked absorption was produced by tributyl phosphate, as shown in Fig. 3 8-e. Fig. 3 8-d shows emission from CN at 359 Emission detected from the unmodulated flame was appre ciable. Fig. 3 8-g shows the spectrum of pyridine detected from the unmodulated flame when the beam from the tungsten lamp was blocked.
Fig. 39 shows absorption spectra obtained at a flame height of 2 cm.
Fragment absorption bands are considerably less in tense than at a flame height of 0.75 cm* However, the absorption produced by the tributyl phosphate and dimethyl sulfoxide samples over wide spectral regions was more intense than at 0.75 cm above the burner. See Figs. 39~c and 39~d.
Fig. b-0 shows absorption scans obtained at 3 cm above the burner.
No fragment absorption bands were observed. Absorp tion was produced by tributyl phosphate and dimethyl sulfoxide sol vents, as shown in Fig. hO-b.
The absorption over wide spectral regions that was produced by solvents containing phosphorus and sulfur was attributed to the species that produced emission spectra in the same region, as discussed on page h9 of this thesis, i.e., to P0 and SO2 fragments
(I1*-, 198). Hg
No Flame.
400 — 1— ------500 60 0 nm
ro Fig. 38-a. Tungsten Lamp -0 Slit O.^O mm. Gain J.h.
Oxygen: 3 o l/min. Hydro'^on: 10 l/min.
CH
CH
^0 0 500 128
Fig. 38-b. Flame Absorption Spectrum of Benzene at a Height of 0.7b cm- Oxygen: 3>3 l/min. Hydrogen: 10 l/min.
Na
CH CH
— i— 500 t- 1 iv o Fig. 38-c. Flame Absorption Spectrum of Butyl Alcohol at a Height of 0.70 cm• Slit O.^O mm. Gain 7*^
Oxygen: 3-5 l/min. Hydrogen: 10 l/min,
Na
Cp
CN CN
CH CH CN
500 6 0 0 nm H c Fig. 38-d. Flame Absorption Spectrum of Pyridine, at a Height of 0.78 cm- Slit 0.50 mm. Gain 7*^ •
Oxygen: 5*5 l/min. Hydrogen: 10 l/min.
Hg ,M( v» /’vM V'H'i /Vf’VA\ ,1
fi 'i Li,W i f < fJS\ i ' f l V I f
Na
1^00 500 600 nm
Fig. _j8-e. Flame Absorption Spectrum of Tributyl Phosphate at a Height of 0.7l cm. CH
Oxygen: 3 .5 l/min. Hydrogen: 10 l/min.
Hoo 500 600 nm H Fig. 38-f. Flame Absorption Spectrum of Dimethyl Sulfoxide at a Height of 0.73 c^- ro Slit 0.50 mm. Gain T-*;-
Oxygen: 3*5 l/min. Hydrogen: 10 l/min.
CH CN
CH CN CN
Na
400 500 600 m: H ve; Fig. 38"8 * Emission Spectrum of Pyridine from the Unmodulated Flame at a Height of 0.75 cm. u
CH
Ga
Oxygen: 3-5 l/min. Hydrogen: 10 l/min.
koo 500 600 nr.: H Fig. 39-a. Flame Absorption Spectrum of Benzene at a Height of 2 cm. , v N ’
Na
Slit O.^O mm. Gain
Oxygen: 3-5 l/min. Hydrogen: 10 l/min.
koo 500 60 0 nm H Fig. 39-b. Flame Absorption Spectrum of Pyridine at a Height of 2 cm. Slit 0.30 mm. Gain 7*-'-.
Oxygen: 3*5 l/min. Hydrogen: 10 1/min.
Hg
\\K
Na
If 00 500 6oo n m
Fig. 39-c* Flame Absorption Spectrum of Tribntyl Phosphate at a Height of 2 C” Na
Oxygen: 3*5 1/min. Hydrogen: 10 l/min.
ifOO 500 600 nm H Fig. 39~d. Flame Absorption Spectrum of Dimethyl- Sulfoxide at a Height of 2 cm. Slit 0.50 nm. Gain 7.F
Oxygen: 3-5 l/min. Hydrogen: 10 l/min
ItOO 500 600 nm H n-; Co Fig. kO-a. Flame Absorption Spectrum of Pyridine at a Height of r? cm. Slit 0.50 mm. Gain J.h .
Oxygen: 3 .5 l/min. Hydrogen: 10 l/min.
------1------— --- 1------1------it-00 500 600 n m H
Fig. U0-b. Flame Absorption Spectrum of Tributyl Phosphate at a Height of y cm. lhO
5■ Absorption Profiles for Fragments
Absorption profiles were obtained at several wave lengths by measuring the intensity of absorption at selected flame heights. The diameter of the beam from the hydrogen or tungsten lamp as it passed through the flame was 0.1-0.2 cm. The emission signal from the unmodulated flame was also recorded. The absorption and emission signals for the flame alone were subtracted from the emis sion and absorption signals produced when the sample was aspirated into the flame. The resulting emission and absorption values were at tributed to the sample, and were summed and plotted as a. function of flame height. The profiles are shown in Figs. hi through 50.
Maximum absorption by the OH fragment occurred be tween 1 and p-5 cm above the burner, as shown in Fig. hi. The OH absorption profile agrees with the results from the absorption spec
tra, as shown in Figs. 38-b and 3h-a. A comparison of emission and absorption profiles shows that the OH radical exhibits both maximum emission and maximum absorption at approximately the same height in the flame, that is, in the region of 2 and 3*5 cm above the tip of the burner, as shown in Figs. I 5 and hi.
Maximum absorption by the CH, C 2 , CM, Nil, P0 (2b6 nm), and CS fragments occurred between 0.5 and 2 cm a.bove the burner, with in the reaction zone of the flame. See Figs. h2 through h8. These absorption profiles agree with results from the absorption spectra obtained at flame heights of 0.75) 2, and 3 cm5 as shown in Figs.
55) 5 h , 35> 38) 55) aad ho. The absorption and emission profiles for CH, C2 , CN, and NH fragments are similar. Maximum emission and absorption occur within the reaction zone. See Figs. 16 through 19 L' 1 u 11 e i; ,11t y c hi )
Oil
0 00 100 Relative Intensity
Rig. 91 . Flame Absorption Profile at OOP nm.
No solvent. Slit 0 . pO nm. Gain 5>9-
F1 n me Height (cm)
CH
0 20 100 Relative Intensity
F i g. 0 2. FIa me Absorption Profile at 2 01 n m.
Benzene was sprayed into the flame.
Slit 1 . 2p mm. Gain 6.1. ±'l 2
F1 >11:10 Height (cm)
1 t
0 20 100 Relative Intensity
Fig. 1-;j. Flame Absorption Profile at -j-foo nm.
Benzene was sprayed into the fla.rae.
Slit 0.50 mm. Gain "(,2,
x' 1 xie Height (cm)
C.
0 20 60 100 Relative Intensity
Fig. Ml-. Flame Absorption Profile at glo nm. Benzene was sprayed into the flame.
Slit 0.20 mm. Gain J.2, 1’ I .'I mo IU' i. ght (cm)
CN
0 Co 100 Relative Intensity
Fig. Flame Absorption Profile at Vi6 nm.
Pyridine was sprayed into the flame.
Slit 0.75 mm- Gain 7-2
F 1 a me Ficight (cm)
o
0 20 60 100 Relative Intensity
Fig. 4u. Flame Absorption Profile at 770 nm. Pyridine was sprayed into the flame. Slit 0.50 mm. Gain 6.2. F i . I UK' 111.' i. gh L (c m)
ro
o CO 100 Relative Intensity
Fig. '4-7. I’lame Absorption Profile at ItC nm.
Triethyl phosphate was sprayed into the flame.
Slit 0.75 t.im. Gain 5*o.
Height (cm)
CS and SO
I
0 00 100
Relative Intensity
Fig. hrj. Flame Absorption Profile at PS9 nm. Thiophcne was sprayed into the flame. Slit 0 . 75 mm• Gain 5 ■ 7 ■ Fla me Height (cm)
PO
2"
20 60 100 Relative Intensity
Fig. 6 9. Flame Absorption Profile at 927 nm.
Triethyl phosphate was sprayed into the flame.
Slit 0.75 Gain 5-S.
F lame Height (cm)
SH and SO 1,.--
20 60 100
Relative intensity
Fig. 50. Flame Absorption Profile at 928 nm.
Dimethyl sulfoxide* and thiophene** were sprayed into the flame.
Slit 0.75* Gain 5«8» 146
and Figs. 42 through 46. The absorption profiles at 246 nm and 259 nm are not as similar to the emission profiles at the same wave lengths, although both maximum emission and maximum absorption occur
in the reaction zone. See Figs. 20, 22, k-J, and 48.
Absorption profiles at 327 and 528 nm for the solvents containing phosphorus and sulfur show maximum absorption between 0.5 and p cm above the tip of the burner. See Figs. 49 and 50. The corresponding emission profiles shown in Figs. 21 and 23 exhibit max ima slightly higher in the flame.
Some differences in emission and absorption profiles might be attributed to the different experimental conditions in volved. In the absorption studies the source beam was concentrated in a very small area of the flame, whereas a relatively wide section of the flame was observed in the emission profile studies, possibly allowing appreciable background emission to be detected. Background absorption may have been detected at 327 and 328 nm for the phospho rus and sulfur samples.
4. Absorption of Atomic Lines by Flames and by Organic
Solvents
Spectra showing absorption by the oxyhydrogen flame were obtained using aluminum, bismuth, and zinc hollow cathode lamps.
The diameter of the source beam was not decreased by placing an aper ture between the lamp and the lens focusing the beam in the flame as was done for the hydrogen and tungsten lamps (see page 88). The beams from the aluminum and bismuth lamps were passed through the flame at a. height of 3 cm above the burner. The diameter of the light beam in the flame was 1-1 .5 cm. The beam from the zinc lamp 11 ?
was passed through the flame three times. The highest pass was ap proximately 3.5 cm above the burner and the lowest pass was approxi mately 0.5 cm above the burner. The diameter of the beam as it passed through the flame 3.5 cm above the burner was 1-1.5 cm, and
0.8 cm above the burner the diameter of the. beam was approximately
1 cm.
The zinc ?0J.6 nm line was not absorbed significantly by the OH fragment in the flame. However, the aluminum 308.2 nm and
5 0 9 . 2 nm and the bismuth 3 0 6 .8 nm lines were absorbed strongly. See
Figs. 51 anc* 52. Interferences in atomic absorption caused by ab sorption by the OH fragment have been mentioned on page I 7 of this thes is .
Absorption by flames at low wavelengths is described on page 16 of this thesis. An example is shown in Fig. 53 for the oxyhydrogen flame into which nitroethane was aspirated. The flame by itself absorbed, but the absorption was increased when the sol vent was sprayed into the flame. A more detailed study was made for various atomic lines. See Table XIV.
Absorption signals of flames into which organic sol vents were aspirated and of organic solvent sprays (with no flame burning) were obtained for various atomic resonance lines. See
Tables XIV and XVI. The beam from the hollow cathode lamp was passed through the flame or spray three times. The highest pass was it--5 cm above the burner, and the lowest pass was 0.8 cm above the burner, which was in the rea.ction zone of the flame. The diameter of the beam as i.t passed through the flame or spray it--5 cm above the burner was approximately 1 -1 .5 cm and at 0.8 cm above the burner the he I a Live In to ns i. ty
■ i AL Hollow Cathode
I
Absorption by Oxyhydrogen Flame
300 320 nm
Fig. 31• Absorption of the A1 303.2 nm and 309-2 nm Lines
by the Oxyhydrogen Flame iJ 1 H oilow Ca thode | Absorption, by Oxyhy drogen Flame
1 nm Line by the Oxyhydrogen
F ] a me . iyO
5 Hollow Ca thode
Ab.sorpt ion Flame into which Nitro- ethane was Sprayed
200 2-'r0 n m i' i'. Absorption Produced by Snraying Nitroethane into the Oxv-
hydroecn Flame of Lines from the Ca , A1 , Mg Multielement
liol low Ca thode .
(---- ) Intensity of beam after passing through the flame into
which nitroethane was sprayed. 151
diameter of the beam was approximately 1 cm. Instrumental slit and
gain settings for different resonance lines were comparable. Gas
flow rates were 3-5 l/min. of oxygen and 10 l/min. of hydrogen.
For the results shown in Table XIV the absorption
signal for the oxyhydrogen flame by itself was subtracted from the
absorption signal resulting when the sample was aspirated into the
flame. The emission signal detected from the unmodulated flame when
the light from the lamp was blocked was zero except as noted in
Table XV. For the solvent sprays (Table X V I ) the oxygen flow rate was 3-5 l/min., the hydrogen flow rate was zero, and there was no
flame burning.
Table XIV shows that in general absorption signals
for the flames were significant at low wavelengths. Absorption sig nals were especially high for the flame alone, and when benzene, anisole, butylamine, pyridine, nitroethane, triethyl phosphate, thiophene, and dimethyl sulfoxide samples were sprayed into the flame.
Absorption by the flame alone at low wavelengths was attributed to the oxygen molecule (1^-, I9 8, 199)- The small increase in the ab sorption signal generally produced by aspirating samples (for ex ample cyclohexane) into the flame may be partly attributible to an increase in the flame size, and hence an increase in absorption by the oxygen molecule.
Absorption of lithium, sodium, iron, and potassium lines was high for the flame and for several samples, in particular tributyl phosphate, triethyl phosphate, thiophene, dimethyl sulfoxide, methyl isobutyl ketone, and acetic acid. Some emission from the un modulated flames was also observed at these wavelengths. See Table XV. Absorption and emission signals at these wavelengths can probably be attributed to the corresponding metal impurities.
Table XVI shows that the absorption signals of sev eral organic solvent sprays (benzene, anisole, butylamine, pyridine, nitroethane, and thiophene) are intense at low wavelengths. Ab
sorption by pyridine is also significant at wavelengths as high as
266 nm. These signals result from absorption by whole solvent mol ecules .
The benzene molecule has a strong absorption maximum at 202 nm (e 6 0 0 0) and a weak absorption maximum at 255 nm (e max max approximately 200) (200, 201, 207) as shown in Fig. 57. Table XVI shows absorption of the magnesium 202.5 nm line by benzene, but
there was no significant absorption of the other resonance lines inves tiga'ted.
The anisole molecule has a strong absorption maximum at 217 nm (e 6 7 0 0 ) and an absorption maximum at 2o9 nm (e max max
1780) (202, 207), ns shown in Fig. 55* Table XVI shows the anisole molecule absorbing at wavelengths less than 223 nm.
The amine group has an absorption maximum at 195 nm
^emax ) (201). Butylamine absorbed appreciably a t wavelengths less than 255 nm.
Pyridine has a strong absorption maximum at I95 nm
(e _ oOOO) and also a maximum at 251 nm (e 1700) (201, 207), as m a x max shown in Fig. 36 • Results shown in Ta.ble XVI agree.
Nitroethane has a strong absorption maximum at 201 nm
(e 7 8 5 0 ) and a weak absorption maximum at approximately 280 (e max max
< 2 0 ) , (202-207). The ultraviolet spectrum of nitrohexane (207) is 153
shown in Fig. 56 . The nitroethane spray absorbed appreciably at wavelengths less than 235 nm.
Thiophene has a strong absorption maximum at 231 nm
(e 5620), (200, 207) as shown in Fig. 37« Results shown in Table max
XVI agree.
The small absorption signals shown in Table XVI that are relatively constant for a sample at all of the wavelengths in vestigated are due to scattering by the presence of the solvent drops
in the path of the light.
No significant absorption was observed for cyclohexane,
distilled water, butyl alcohol, amyl acetate, methyl isobutyl ketone,
acetic acid, tributyl phosphate, triethyl phosphate, dimethyl sulfox
ide, chloroform or butyl chloride sprays. Absorption was not ob
served for these samples, or for the benzene sample at wavelengths close to 255 nm, the anisole sample at wavelengths close to 269 nm, or the nitroethane sample at wavelengths close to 280 nm, because
(1.) the molecules did not absorb in the ultraviolet region or at
the wavelengths investigated, or (2.) the absorption (e ) was re- r v max
latively weak. For example, absorption by butyl alcohol is rela
tively weak (205). The ester group has a weak absorption maximum at approximately 205 nm (emax 5 0 ) (201), ketones have a weak absorption maximum in the 27 0 -2 8 5 nm region (e < 3 0 ) (200, 201), acetic acid max has a weak maximum at 208 nm (e 3 2) (2 0 6), and the sulfoxide group max has an absorption maximum at 210 nm (emax ^5 0 0 ) (200, 201).
The relatively high absorption signals at low wave
lengths resulting when benzene, anisole, butylamine, nitroethane, and thiophene samples were aspirated into the flame can be attributed l$k
mainly to absorption by whole, unburned, solvent molecules. See
Tables XIV and XVI. Absorption by pyridine and thiophene molecules
in the flame was also observed in absorption spectra obtained with
the hydrogen lamp. See Figs. JJ-d and 55-g. The relatively high absorption signals observed when triethyl phosphate and dimethyl sul
foxide samples were aspirated into the flame must be attributed to
some species produced in the flame, since there was no significant absorption observed for the triethyl phosphate and dimethyl sulfoxide
sprays. See Tables XIV and XVI. The absorption produced by tri ethyl phosphate in the flames at low wavelengths may be due to the
P2 fragment (I9 8). Absorption produced by dimethyl sulfoxide at low wavelengths is probably due to S02 (152). Some of the absorption produced in the same region by thiophene is probably also due to S02 . 155
Table XIV. Absorption of Atomic Resonance Lines by Oxyhydrogen
Flames into which Organic Solvents were Sprayed
Sample* °j„ Absorption** of Atomic Resonance Lines
Mg Zn Pt Pb Cu Be 202.5 2 1 3 .8 2lk. 8 21 (. 0 222.6 23k nm flame 13 5 3 6 3 0 benzene 15 5 k k 1 2 cyclohexane 1 3 3 2 0 1 distilled water 0 0 l 1 0 0 butyl alcohol 1 0 1 0 0 0 amyl acetate 2 2 2 2 0 0 methyl isobutyl ketone 3 2 k 2 0 0 anisole k 6 6 ' 6 2 0 acetic acid 1 2 1 1 0 0 butylamine 6 8 8 5 2 2 pyridine k k 6 3 2 1 nitroethane 9 6 11 k 2 0 tributyl phosphate 2 k 2 2 1 1 triethyl phosphate 5 9 5 6 2 3 thiophene 2k 28 33 32 18 22 dimethyl sulfoxide 10 12 11 12 5 k chloroform 2 0 1 1 0 0 butyl chloride 2 3 3 2 0 0
** + 2 * Gas flow rates: Oxygen 3*5 l/min, Hydrogen 10 l/min. 156 (Table XIV continued) Sample* p/, Absorption** of Atomic Resonance Lines Co Cu Co Pt Mg Pb 240.7 249.2 252.1 265.9 279.6 283.5 nm flame 2 1 1 0 0 2 benzene 1 0 0 0 0 0 cyclohexane 0 0 0 0 0 0 distilled water 0 0 0 0 0 0 butyl alcohol 0 0 0 0 0 0 amyl acetate 0 0 0 0 0 0 methyl isobutyl ketone 0 0 . 0 0 0 0 anisole 0 0 0 0 0 0 acetic acid 0 0 0 0 0 0 butylamine 0 0 0 0 0 0 pyridine 2 2 4 0 0 0 nitroethane 0 0 0 0 0 0 tributyl phosphate 0 0 0 0 0 1 triethyl phosphate 2 2 3 2 2 2 thiophene 16 6 6 4 4 5 dimethyl sulfoxide 4 2 2 2 2 • 2 chloroform 0 0 0 0 0 0 butyl chloride 0 0 0 0 0 0 ** + 2.°j0 absorption. * Gas flow rates: Oxygen 3-5 l/min.; Hydrogen 10 l/min. 15 (Table XIV continued) Sample* o/n Absorption** of Atomic Resonance Lin< Mg Zn V Li Cu Ag 2 8 5 .2 307.6 3 1 8,A 3 2 3..3 3 2 ^ .8 328 nm f 1 ame 0 0 0 17 0 1 benzene 0 0 0 8 0 0 cyclohexane 0 0 0 6 0 0 distilled water 0 0 0 3 0 0 butyl alcohol 0 0 0 2 0 0 amyl acetate 0 0 0 3 0 0 methyl isobutyl ketone 0 0 0 3 0 0 anisole 0 0 0 , 6 0 0 acetic acid 2 0 0 0 0 0 butylamine k 0 0 2 0 0 pyridine 0 0 0 5 0 0 nitroethane 0 0 0 3 0 0 tributyl phosphate 2 0 0 ' 25 0 2 triethyl phosphate 2 2 2 39 2 3 thiophene It 3 3 31 2 2 dimethyl sulfoxide 2 2 1 21 0 1 chloroform 0 0 0 2 0 0 butyl chloride 0 0 0 3 0 0 ** + 2^ absorption, * Gas flow rates: Oxygen 3-5 l/min.; Hydrogen 10 l/min. 158 (Table XIV continued) Sample* o/, Absorption** of Atomic Resonance Lint Na A g Cr Fe W ^ — r 3 3 0 . 2 3 3 8 . 3 35 7 . 9 386.,0 4 0 0 . 9 -P" O nm flame 0 0 0 0 0 0 benzene 2 0 0 0 0 1 cyclohexane 2 0 0 0 0 0 distilled water 0 0 0 0 0 0 butyl alcohol 0 0 0 0 0 0 amyl acetate 0 0 0 0 0 0 methyl isobutyl ketone 1 0 0 0 0 0 anisole 2 0 0 0 0 0 acetic acid 0 0 0 0 0 0 butylamine 1 0 0 0 0 0 pyridine 1 0 0 2 0 0 nitroethane 0 0 0 0 0 0 tributyl phosphate 16 0 0 7 0 1 3 triethyl phosphate 2 k 1 0 1 8 0 2 b thiophene 28 1 0 3 0 6 dimethyl sulfoxide 10 0 0 2 0 2 chloroform 0 0 0 0 0 0 butyl chloride 0 0 0 0 0 0 ** + 2^ absorption. * Gas flow rates: Oxygen 3*5 l/min.; Hydrogen 10 l/min. 159 (Table XIV continued) Sample* 4t Absorption** of Atomic Resonance Lines Ca Ba. Na Li K 122.7 553.6 5 8 9 .0 670.:8 7 6 6 .5 n m flame 0 0 0 0 1 benzene 0 0 0 0 0 cyclohexane 0 0 0 0 0 distilled water 0 0 2 0 0 butyl alcohol 0 0 2 0 0 amyl acetate 0 0 6 0 0 methyl isobutyl ketone 0 0 29 0 0 anisole 0 0 0 0 0 acetic acid 0 0 ■ l b 0 0 butylamine 2 0 b 0 0 pyridine 0 0 0 0 0 nitroethane 0 0 2 0 0 tributyl phosphate 0 0 2 0 0 triethyl phosphate 1 0 0 1 2 thiophene 0 0 0 0 0 dimethyl sulfoxide 0 0 2 • 0 0 chloroform 0 0 0 0 0 butyl chloride 0 0 0 0 0 ** + 2 * Gas flow rates: Oxygen 3-5 l/min.; Hydrogen 10 l/min. Table XV. Emission S ignats from Unmodulated Sample* 4) Emission** Li Na Fe K 523.3 330.2 386.0 nm flame 1+ benzene 5 cyclohexane 2 distilled water k anisole 3 butylamine 1 pyridine 2 nitroethane 1 tributyl phosphate 18 1 triethyl phosphate 16 10 2 thiophene 16 18 dimethyl sulfoxide IT ** + 2 * Gas flow rates: Oxygen 3-5 l/min.; Hydrogen 10 l/min. 161 Table XVI. Absorption of Atomic Resonance Lines by Solvent Sprays* Sample* °l, Absorption** of Atomic Resonance Lines Mg Zn Pt Pb Cu Be 2 0 2 .5 2 1 3 .8 217 2 1 7 .0 2 2 2 .6 237.9 nm benzene 58 1+ 7 7 2 2 cyclohexane 5 1 3 2 1 1 distilled water 7 7 5 7 3 2 butyl alcohol 1 2 3 2 l 1 amyl acetate 5 6 7 6 7 7 methyl isobutyl ketone 6 6 6 6 7 7 anisole 12 23 27 20 6 2 acetic acid 7 5 7 7 2 2 butylamine 16 22 28 27 17 6 pyridine 8 7 7 6 7 10 nitroethane 72 3 b 37 27 8 7 tributyl phosphate 2 1 3 7 2 2 triethyl phosphate b 5 5 7 7 thiophene 29 62 70 68 60 80 dimethyl sulfoxide 7 7 5 7 2 2 chloroform b 2 2 3 0 1 butyl chloride 2 3 3 7 2 2 ** + 2 * No flame. Oxygen flow rate: 3*5 1/min. 1 6 2 (Table XVI continued) Sample* qf,Absorption** of Atomic Resonance Lines Co Cu Co Pt Mg Pb 2 ^ 0 .7 2^9.2 252.1 2 6 5 .9 2 7 9 .6 2 8 5 .5 nm benzene 3 3 k b 2 k cyclohexane 2 1 2 2 2 2 distilled water k 2 4 k b k butyl alcohol 2 2 2 2 2 2 amyl acetate 6 5 6 k 6 methyl isobutyl ketone 6 k 6 6 6 6 anisole b 2 k 6 3 4 acetic acid 3 2 2 3 2 k butylamine b b b k 3 b pyridine 16 15 20 11 5 5 nitroethane 5 k k 5 5 6 tributyl phosphate 2 2 2 3 2 3 triethyl phosphate 5 k k 5 U 6 thiophene 36 2 3 2 2 4 dimethyl sulfoxide 2 2 2 3 2 b chloroform 2 2 2 2 2 2 butyl chloride 2 2 k 2 it- ** + 2«& absorption. * No flame. Oxygen flow rate: 5-5 l/min. 1 6 5 (Table XVI continued) Sample* g£Ab sorption** of Atomic Resonance Lines Mg Zn V Li Cu Ag 2 8 5 .2 5 0 7 .6 3l8.k 323.3 32k . 8 ro CD nm benzene k k k k 3 k cyclohexane 2 2 2 2 2 2 distilled water 1|. 5 k 3 k butyl alcohol 2 2 5 k 2 2 r r amyl acetate O O S 8 6 6 s' methyl isobutyl ketone 6 6 8 0 6 6 anisole k 5 6 C k k acetic acid k ii- k . 5 3 k butylamine k ii. 6 6 3 k pyridine k 5 5 k k nitroethane 6 6 7 5 6 6 tributyl phosphate 2 k 1; 5 2 2 s' r triethyl phosphate 6 0 7 O 5 0 thiophene 2 5 k k It- k dimethyl sulfoxide 2 5 k k 'ZJ 2 o chloroform 2 2 3 3 2 t . 1 , butyl chloride 5 k 5 3 14. 2 ** + 2«p absorption. * No flame. Oxygen flow race: 5-5 l/min. (Table XVI continued) Sample* % Absorption** of Atomic Resonance Lines Na Ag Cr Fe W K 330.2 338.3 357-9 386.0 400.9 4o4.4 benzene 2 4 2 3 4 3 cyclohexane 2 1 2 2 3 2 r distilled water 3 3 O 5 4 4 butyl alcohol 2 2 2 2 2 2 amyl acetate 6 5 6 7 8 6 methyl isobutyl ketone 5 6 6 6 8 6 anisole 4 4 5 4 4 4 acetic acid 3 2 4 . 4 4 2 butylamine 4 3 4 5 5 4 pyridine 4 3 • 4 5 4 4 nitroethane 4 5 6 6 6 5 tributyl phosphate 2 2 3 4 4 3 triethyl phosphate 5 4 6 8 6 5 thiophene 2 2 3 3 4 3 dimethyl sulfoxide 3 2 4 5 4 3 chloroform 2 2 2 2 3 2 butyl chloride 2 2 3 4 4 4 ** i ^ absorption. * No flame. Oxygen flow rate: 3-5 1/min. 165 (Table XVI continued) Sample* rfn Absorption** of Atomic Resonance Lines Ca Ba Na Li K 422.7 553.6 589.0 670.8 7 66 benzene 4 3 4 4 4 cyclohexane 2 2 2 2 4 distilled water 4 5 4 4 6 butyl alcohol 2 2 3 2 4 amyl acetate 8 6 8 8 10 methyl isobutyl ketone 8 6 6 7 9 anisole 6 4 6 6 4 acetic acid 3 4 4 4 4 butylamine 4 4 5 6 7 pyridine 4 4 4 4 5 nitroethane 6 6 6 • 7 8 tributyl phosphate 5 4 4 3 4 triethyl phosphate 6 6 6 6 8 thiophene 4 4 4 4 5 dimethyl sulfoxide 3 4 4 4 4 chloroform 2 2 2 2 4 butyl chloride 4 3 4 4 6 ** + 2vjo absorption. * No flame. Oxygen flow rate: 5-5 l/mln. A b.r or bonce O.A t 1.0 2 .0 -r. 200 220 Fis. Abro T 90 Sad tier uv I'Ob A b s o:'l>nne v 0 .0 -- i.o-- 1 - 5 " 2 -0 ^ 200 220 Fir,. c)j . Absorption Spnc irun■ of7 Anifolo ->: Sadtler uv O v ’’ (-'0V) 1 9.0-._ ? ig. [j '-j . Absorption Spoc crr.av of I-n-nitrohaxanc in ]. 0 Ethanol A Xcr.iuia, W. and Turriowska-Rubasowska, W. , Roczniki Chain., ~>7, 199Y (-995), Fig. l, p. 1 9 9 0. SUMMARY Emission and absorption spectra produced by aspirating organic solvents into oxyhydrogen flames have been investigated in order to add to the knowledge of the physical and chemical processes oc curring in flames, analytical procedures for determining organic compounds in flames, and spectral interferences observed in flame photometry, atomic absorption, and atomic fluorescence. Emission and absorption spectra, are presented. The most prom inent bands are listed according to wavelength and species emitting or absorbing. In addition to distinct bands, compounds containing phosphorus or sulfur produced spectra over relatively wide wave length regions. The effects of flame height on emission and absorption spectra were investigated and flame profiles for various species are pre sented. Maximum emission and absorption by organic fragments oc curred in the reaction zones of the flames. Emission and absorption by the OH fragment and by flames into which compounds containing phosphorus and sulfur were aspirated was intense above as well as within the reaction zone. The effects of varying the hydrogen to oxygen ratio and of aspirating with hydrogen instead of oxygen were investigated with respect to emission spectra. Sensitivity estimates for CH and NH emission were obtained. Absorption by whole solvent molecules in flames and by frag ments in flames was observed. Absorption by organic solvent 169 1-fO molecules agree with results obtained by conventional spectrophoto- ;r.etry. Jpoctra showing absorption of atomic lines by flame and sol vent species are presented. Tables of absorption signals produced by flames into which solvents were aspirated and also by whole sol vent molecules are presented for various atomic resonance lines. "A1though it is desirable for a user to ... have some information regarding interference possibilities, ... until enough is on record regarding his particular instrument, the in- forma.Lion to be found in the literature must be regarded as a warning of what might happen" . 8 3 Jones , A.G. j Analytical C'nemis f - S ome New Techniques , Academic Press, Inc., New York, I9b9> P- 21. REFERENCES The bibliography is divided into several groups corresponding to the subject matter covered in the text. When a reference is per tinent to more than one subject group it is listed with the group that appears first in the bibliography or with the group in which it best fits. A. REFERENCES OH THE GENERAL REVIEW OF FLAMES AND FLAME PROCESSES 1. References on the General Background 1. Fristrom, R.M. and Westenberg, A.A., Flame Structure, McGraw- Hill Book Co., New York, I 965 • 2. Fristrom, R.M., "Flame Chemistry," Survey of Progress in Chem istry , J3, 55 (1 9^6 ). p. Fristrom, R.M., "The Mechanism of Combustion in Flames," Chem. Eng. News, hi, (hi), 1 5 0 (I9 6 5 ). k. Williams, F.A., Combustion Theory; The Fundamental Theory of Chemically Reacting Flow Systems, Addison-Wcsley Pub. Co., Inc., Reading, Mass., 19&5• 5. Anderson, R.C., "Combustion and Flame," _J. Chcm. Educ. , 'hi-, 2k 8 (I9 6 7). 6. Gaydon, A.G. and Wolfhard, H.G., Flames, their Structure, Radi- ation, and Temperature, 2nd ed., Chapman and Hall, Ltd., London, i9 6 0. 7. Lewis, B. and Von Elbe, G., Combustion, Flames, and Explosions of Gases, 2nd ed., Academic Press, Inc., New York, I9 6I. 8 . Wehner, J.F., "Flame Processes, Theoretical and Experimental," Advan. Chem. E n g . , 5., 1 (IS)6k ) . 9 . Pungor, E., Flame Photometry Theory, D. Van Nostra.nd Co., Ltd., London, I9 6 7. 10. Minkoff, G.J. and Tipper, C.F.H., Chemistry of Combustion Re actions , Butterworths, London, I9 6 2. 171 172 11. Liutlowood , K. , "Combustion Chemistry of Hydrocarbons Br i t. C h e m . bni".. , _0, of’ (lyo7). 12. Fenimore , C . P. , Chemistry in Premixed Flames, The Macmillan Co., New York, 1687. 2. References on Flame Spectroscopy i;3. Walker, S. and Straw, II., Spectroscopy, Vol. II, pp. 271-275 > The Macmillan Co., New York, 1$»62. 17. Caydon, A.G., The Spectroscopy of Flames, John Wiley and Sons, Inc., New York, 195?. Ip. Gaydon, A.G., "Spectra of Flames," Advan. S pec try. , Vol. II, Intcrscience Pub., Inc., New York, I9 6I. 16. Laud, B.li. and Sathe, L.N., "Spectroscopic Study of Some Or ganic Flames: Part 1 - Variation of Band Intensity of Differ ent Radicals with Air-Fuel Composition and Influence of Di luents," Indian J. Pure Appl. Phys. , h_, 7 (I9 6 0). If. Mavrodineanu, R. and Boiteux, H., Flame Spectroscopy, John Wiley and Sons, Inc., New York, I9 6 5 . 16. McEwan, M.J. and Phillips, L.F., "Use of the Li/LiOH Method for Measuring III] in Low-temperature Flames," Combus t. Flame, 9 , 720 (1965). 19. Gaydon, A.G., Spokes, G.N., and Van Suchtelen, J., "Absorption Spectra of Low-pressure Flames," Proc. Roy . Soc. , Ser. A ., 29 6, 32y (I9 6 0). 20. Bleekrode, R. and Nieuwpoort, W.C., "Absorption and Emission Measurements of Co and CH Electronic Bands in Low-Pressure Oxyacetylene Flames," _J. Chem. Phys., 7 9, 9680 (1 9 6 5 ). 21. Porter, 11.P., Clark, A.II., Kaskan, W.E., and Browne, W.E., "A Study of Hydrocarbon Flames," Symp. Combust., 11th, The Com bustion Institute, Pittsburgh, 907> 1967- 22. Becker, K.H. and Bayes, K.D., "CO Chemiluminescence from Flames," _J. Chem. Phys. , 78, 653 (I9 6 8). 23. Hornbeck, G.A. and Herman, 11.C., "Hydrocarbon Flame Spectra," Ind. Eng. Chem., 7b, 2739 (1951). 27. Jessen, P.F. and Ga.ydon, A.G. , "Study of the Absorption Spectra of Free Radicals in Flames," Combust. Flame, 11, 11 (1 9 6 7). 25. Bulewicz, E.M., "Some Observations on Chemiluminescence and Chemi-ionization in Flames," Combust. F1a me, 11, 297 (1967)- 173 2o. Diokc, G.H., "Spectroscopy of Combustion." In I'. Lewis, R.N. Pease, and U.S. Taylor, (Eds.), High Speed Aerodynnmi.es and Jet Propu Is ion, Vol. IX, Physical. Measurements in Gas Dynamics and Combus I; ion, Princeton University Press, Princeton, N.J., 1957. OJ . I'.cb ig o , R. , "A Study on the Radiation of Luminous Flarnes," S yir.p . Combus t. , II tli, The Combustion Institute, Pittsburgh, 3 8 1, 1997. 28. Robinson, J.W. and Smith, V., "Emission Spectra of Organic Liquids in Oxy-Hydrogen Flames," Anal. Cnim. Ac ta , '}>6, 789 (i9 6 0). 2 9. Kirkbright, G.F., Peters, M.K., and West, T.S., "Emission Spec tra of Nitrous Oxide Supported Acetylene Flames at Atmospheric Pressure," Talanta , 13 . 789 (19)6 7) • 9. References on Some Energy Aspects of Flames pO. Von Engel, A., "Collisions in Gases and Flames Involving Exci ted Particles," Brit. _J. Appl. Phys. , 18, l6 6l (1 9 6 7). pi. Tawde, N.R. and Laud, B.B., "Spectral Intensity Distribution and Equilibrium of Flame Gases," Indian J. Pure Appl . Phys. , IL, 90 (!9o3). 32. Laidler, K.J. and Shuler, K.E., "Kinetics of Combustion— Rela tion to Emission Flame Spectroscopy," Ind. Eng. Chem., 2758 (1951). 33- DeGalan, L. and Winefordner, J.D., "Thermal Equilibrium in Turbulent Diffusion Flames," _J. Quant. Spectry. Radiactive T r a n s f e r , _][, 7 0 3 (1 9 6 7). 37. Sugden, T.M., "Excited Species in Flames," Ann. Rev. Phys. Chem„, 13, 369 (1 9 6 2). k . References on Chemical Reactions in Flames 35. Franklin, J.L., "Mechanisms and Kinetics of Hydrocarbon Combus tion," Ann. Rev. Phys. Chem., 18, 2ol (1 9 6 7). 3 6 . Ashmore, P.G., "Elementary Combustion Reactions. Neutral Species," S ymp. Combus t., 10 th , The Combustion Institute, Pittsburgh, 377 > l9o5 ■ 37• Minkoff, G.J., "Instrumentation for the Study of Free Radicals." In J. Surugue (Ed.), Experimental Methods in Combustion Research, North Atlantic Treaty Organization, Advisory Group for Aero space, Research and Development, Pergamon Press, New York, 1 9 6!. 3 8. Miller, W.J., "Ionization in Combustion Processes," Oxidation Combust. Rev. , J5, 97 (I9 6 8). Sugden, T.M., "Elementary Combus tion Ruac Lion;;. Charged S p e cie:;", vjULl - C o mbu s 1:. , .1 O th , The Combustion Ins t i. Lu Le , Pitts burgh, bit, 1'Xi1,. llomann, K.H., and Wagner, 11.G., "Chemistry of Carbon Formation in F Lamas 1’roc . Roy. Soc. , Sor. A , 807, l7l (I9 6 8). Fenimore, C.P. and Jones, G.W., "Comparative Yields of Soot from Premixed Hydrocarbon Flames," Combus t. F 1 a me , 12 , l cj6 (I9 6 8). Tesner, P.A., Robinovitch, H.J., and Rafalkes, I.S., "The Forma tion of Dispersed Carbon in Hydrocarbon Diffusion Flames," Symp. Combus t., 8 th, Williams and Wilkins Co., Baltimore, 801, I9 6 2. Seedling, F.C., Frazee, J.D., and Anderson, R.C., "Mechanisms of Nucleation in Carbon Formation," S ymp. Combus t, 8 Lh, Williams and Wilkins Co., Baltimore, 777, I9 6 2. Palmer, II.B. and Cullis, C.F., "The Formation of Carbon from Gases". In P.L. Walker (Ed.), Chemistry and Physics of Carbon, Marcel Dekker, Inc., New York, 1 9 6 5 . Courtney, W.G., "Condensation During Heterogeneous Combustion," Symp. Combust. , 11th , The Combustion Institute, Pittsburgh, 287, 1967. Chakrabarty, B.B. and Long, R . , "The Formation of Soot and Poly- cyclic Aromatic Hydrocarbons in Diffusion Flames III — Effect of Additions of Oxygen to Ethylene and Ethane Respectively as Fuels Combus t. F 1 a m e , 1 2 , 8 6 9 (1 9 6 8). Fish, A., "The Cool Flames of Hydrocarbons," Angew. Chem. Intern Ed. Engl., 7, Ip (1968). Burt, R., Skuse, F., and Thomas, A., "Kinetic Spectroscopy of Intermediates in Reactions Leading to Ignition of Hydrocarbons," Combust. Flame, 9, I 59 (I965 ). In W. 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K i r c h o f f , G. and B u n s e n , R. , Phil. Mag., 2 0 , 69 (i8 6 0). K i r c h o f f , G. and B u n s e n , R. , Phil. Mag., 52, 329 (1861) • K i r c h o f f , G. and Bunsen, R. , Ann. Chim. Phys., 62, 7-52 (1 8 6 1) K i r c h o f ! , G. and B u n s e n , R. , Pogg. Ann. d. Physik, 3.18, 357 (1 8 6 1). 52. Lundegardh, H . , The Quantitative Spectral Analys is of the Ele ments , G. Fischer, Jena, Vol. I (1 9 2 9), Vol. II (1957). 55. Mavrodincanu, R., "Some Considerations on Burners for Flame Spectroscopy," Dove lop . A p p l . Spec tr . , _5_, 3 7I (i9 6 0). 57. Parsons, M.L. and Wincfordner, J.D., "Optimisation of the Cri tical Instrumental Parameters for Achieving Maximum Sensitivity and Precision in Flame — Spectrometrie Methods of Analysis," Appl. Spec try., 2 1 , 5 6 8 (I9 6 7). 55- Dean, J.A., Flame Photometry, McGraw-Hill Book Co., Inc., New York, i9 6 0. 56. Dean, J.A., "New Developments in Practice and Technique of Flame Spectrometry," Develop . Apnl. 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MCA Serial No. 60, Washington. 206. Dyer, J.R. , Anp'l. ica tlons of Absorption S pec troscopy of Organic Compounds , Prent ice-IIal 1, Inc., Englewood Cliffs, New Jersey, 1 9 6 5 . i6y Sadi:.Ior i:i lira Violol; SmicLrri, Sod tier lie sc a r c h Laboratories Philadelphia. VITA Vega Joan Out Smith was born on February ly , 1937. In 1 [j'/j she received a. Bachelor ol Science degree in Chemistry from the Univer sity 01: Alabama. he tween i f 0 9 and lyol she was employed by the United States Department of Agriculture in New Orleans, Louisiana. In 1 9 o i she was married to William Kennedy Smith. Between I9 6I and 1god she was employed by Southern Research Institute ana the Univer sity of Alabama Medical School in Birmingham, Alabama. In 196*1 she was admitted to Louisiana State University. Presently she is a candidate for the degree of Doctor of Philosophy in Chemistry. EXAMINATION AND THESIS REPORT Candidate: Vega Jean Smith Major Field: Chemistry- Title of Thesis: Ultraviolet Emission and Absorption Spectra Produced by Organic Compounds in Oxyhydrogen Flames Approved: Major Professor and Chairman Dean of the Graduate School EXAMINING COMMITTEE: & f . >X0 ( j L p ~ Date of Examination: ______June 12, 1 9 6 9