DOCSLIB.ORG

Ion Fragmentation of Small Molecules in Mass Spectrometry

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Ion Fragmentation of Small Molecules in Mass Spectrometry Ion fragmentation of small molecules in mass spectrometry Jeevan Prasain [email protected] 6-2612 J. Prasain 01/19/11 Nomenclature: the main names and acronyms used in mass spectrometry • Molecular ion: Ion formed by addition or the removal of one or several electrons to or from the sample molecules- Electron Impact (EI-MS). M + e- M+• + 2e- • Adduct Ion: Ion formed through interaction of two species and containing all the atoms of one of them plus one or several atoms of them (e.g. alkali, ammonium). J. Prasain 01/19/11 1 Contd.. • Pseudomolecular ion: Ion originating from the analyte molecule by abstraction of a proton [M-H]- or addition of proton [M+H]+ • Tandem mass spectrometry (Cooks, 1976): MS/MS (McLafferty, 1978), tandem in space or time • Precursor ion/parent ion: Ions undergoing fragmentation. • Product ion/daughter ion: Ions resulting from parent/precursor ions. • Neutral loss: Fragments lost as neutral molecules • In positive ionization mode, a trace of formic acid is often added to aid protonation of the sample molecules; in negative ionization mode a trace of ammonia solution or a volatile amine is added to aid deprotonation of the sample molecules. Proteins and peptides are usually analysed under positive ionization conditions and polyphenols and acids under negative ionization conditions. In all cases, the m/z scale must be calibrated. J. Prasain 01/19/11 Terminology.. • Ionspray denotes pneumatically assisted ESI operating at aflow rate of approximately 5 to 50 uL/min. • Turboionspray is ionspray with additional heated gas for flow rate of 0.1 to 2 ml/min. • Heated nebulizer is the trade mark of AB Sciex for APCI. J. Prasain 01/19/11 2 What is Collision Induced Dissociation (CID) or Collisionally Activated Dissociation (CAD) ? Fragmenting ion Collision gas Collision cell o o o o o o o o o o o o Product ions Precursor ion o or parent ion Activated ion Neutral loss Schematic of CID fragmentation Other activation processes: PSD (post source-decay) ECD (electron capture dissociation) SID (surface-induced dissociation J. Prasain 01/19/11 Various types of MS/MS experiments Hopfgartner etal. J. Mass Spectrom, 2004 J. Prasain 01/19/11 3 Steps involved in fragmentation Step # 1: Creation of ions C N OCH2CH3 ESI H Step # 2: Add energy of activation CID Step # 3: Charge directed fragmentation Fragment ion + neutral molecule J. Prasain 01/19/11 Applications of MS/MS • Identification and characterization drug metabolites • Authentification and profiling of chemical components in a crude mixture • Substructure analysis of unknown components • Quantification of analytes in biological samples J. Prasain 01/19/11 4 Ways to approach predicting MS/MS • Likely sites of protonation or deprotonation. • Likely leaving group. • Mobility of protons CH OH • Literature study HO 2 O HO HO OH O OH Where are the sites of HO OH Deprotonation/protonation? O O COOH What is the most likely leaving O Group in this molecule? Fragmentation always follows the basic rules of chemistry J. Prasain 01/19/11 Ion fragmentation for identification of phase II drug metabolites (glucuronide/sulfate conjugates) J. Prasain 01/19/11 5 What fragment ions are characteristics for glucuronide conjugates? Product ion spectrum of genistein glucuronide in ESI-MS/MS 100 269 COOH Aglycone O genistein HO OH OH 445 50 Characteristic fragments Parent Neutral loss (176 Da) Relative Relative Intensity (%) ion 85 59 113 133 181 224 0 100 200 300 400 m/z Glucosides/glucuronides conjugates are easily cleaved off by higher potential at orifice J. Prasain 01/19/11 The loss of 80 Da from the parent ion and the presence of m/z 80 in the product ion spectra are the indicative of sulfate conjugates of phenolic compounds like daidzein [A] and equol [B] 116.9 O O 5.5e6 S O O- HO O 4.5e6 [A] Intensity, cps Intensity, 3.5e6 253.0 O 2.5e6 1.5e6 134.9 224.0 80.091.0 132.9 252.0 5.0e5 207.9 96.9 160.0 197.0 225.0 20 60 100 140 180 220 260 300 121.0 1.4e7 O- O 1.2e7 [B] O S O 1.0e7 O Intensity, cps Intensity, 8.0e6 119.0 6.0e6 135.0 4.0e6 79.9 OH 2.0e6 93.0 241.0 147.0 91.0 320.9 20 60 100 140 180 220 260 300 340 m/z, amu J. Prasain 01/19/11 6 What happens with aliphatic sulfates in MS/MS? Aliphatic and aromatic sulfate conjugates behave differently in MS/MS aliphatic typically show m/z 97 (HSO4-) and m/z 80 (SO3-.) J. Prasain 01/19/11 The absence of the m/z 97 fragment with the base peak m/z 80 makes the distinction between aromatic and aliphatic sulfates Source: Weidolf et al. Biomed. and Environ. Mass Spec. 15, 283-289, 1988 J. Prasain 01/19/11 7 Change in mass is associated with possible metabolic reaction Metabolic rxn Change in mass Methylation 14 Demethylation -14 Hydroxylation 16 Acetylation 42 Epoxidation 16 Desulfuration -32 Decarboxylation -44 Hydration 18 Dehydration -18 J. Prasain 01/19/11 Characteristic fragmentation of drug conjugates by MS/MS Conjugate Ionization mode Scan Glucuronides pos/neg NL 176 amu Hexose sugar pos/neg NL 162 amu Pentose sugar pos/neg NL 132 amu Phenolic sulphate pos NL 80 amu Phosphate neg Precursor of m/z 79 Aryl-GSH pos NL 275 amu Aliphatic-GSH pos NL 129 taurines neg Precursor of m/z 124 N-acetylcysteins neg NL 129 amu J. Prasain 01/19/11 NL = neutral loss. 8 How steroids get fragmented in MS/MS? +OH2 +OH2 6.5e6 107.1 5.5e6 HO + + m/z 135 4.5e6 m/z 107 135.1 HO Intensity, cps Intensity, 3.5e6 m/z 159 HO 2.5e6 159.0 Estradiol 1.5e6 109.1121.2133.0 m/z 273 81.1 93.1 147.1 173.1 5.0e5 145.1 20 60 100 140 180 220 260 133.1 8.4e6 O OH+ 159.1 6.5e6 157.1 Intensity, cps Intensity, 4.5e6 HO 2.5e6 197.1 Estrone m/z 271 145.1 107.1 171.1 81.1 213.1 93.1 121.2131.1 183.0 198.1 253.2 5.0e5 79.1 105.1 141.1147.1 179.1 20 40 80 120 160 200 240 J. Prasain 01/19/11 Estradiol Standard Curve 0.05 – 25 µM r = 0.9959 Untitled 1 (Estradiol 273.2 / 107.1): "Quadratic" Regression ("1 / (x * x)" weighting): y = -215 x^2 + 1.7e+004 x + -104 (r = 0.9959) 3.0e5 2.8e5 2.6e5 2.4e5 2.2e5 2.0e5 1.8e5 1.6e5 1.4e5 Area, counts 1.2e5 1.0e5 8.0e4 6.0e4 4.0e4 Sensitivity is an issue in quantification of steroids 2.0e4 0.0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Concentration, uM J. Prasain 01/19/11 9 Derivatization of estradiol with dansyl chloride leads to the formation of E2-dansyl (m/z 506) Easy protonation Source: Nelson et al. Clinical Chemistry, 2004 J. Prasain 01/19/11 Does derivatization help increase sensitivity? Representative MRM chromatogram (mass transition 506/171) obtained from 50 picomole concentration of dansylated E2 5.62 460 400 340 Intensity, cps Intensity, 280 220 160 5.80 100 6.26 6.627.09 7.80 5.225.50 7.53 8.00 4.88 8.49 40 4.37 8.63 0 1 3 5 7 9 Time, min J. Prasain 01/19/11 10 Calibration curve for dansylated E2 showing linearity from 50 picomole to 100 nanomole concentration range (r = 0.999) 8.0e6 6.5e6 5.0e6 Area, counts Area, 3.5e6 2.0e6 5.0e5 0 10 20 30 40 50 60 70 80 90 100 Concentration, nM J. Prasain 01/19/11 Can MS/MS analysis help distinguish isoflavone glucosides? The Kudzu as a OH source of isoflavones HO CH2OH CH2OH HO O O OH OH O O HO O OH O OH O OH Puerarin; mol. wt. 416 Daidzin; mol. wt. 416 J. Prasain 01/19/11 11 O- and C-glucosides fragment differently in ESI-MS/MS CH2OH O OH O [A] + OH O Yo OH 100 255.050 O OH -162 Da Daidzin m/z 415 % 256.057 [B] 0 100 297.043 HO -120 Da CH OH OH 2 267.037 HO O % HO O 321.046 307.065 268.041 351.044 281.051 335.061 381.055 363.046 OH O 0 220 240 260 280 300 320 340 360 380 m/z Puerarin J. Prasain 01/19/11 m/z 415 Prasain et al. J. Agric. Food Chem. 2003 Possible product ions of puerarin in ESI-MS/MS in negative ion mode OH Prasain et al. J Agric Food Chem. 51, 4213, 2003. HO CH2OH HO O OH HO O -120 Da HO O O O- O- m/z 415 O m/z 295 -90 Da HO -28 Da HO HO O HO O O O- O O- m/z 325 m/z 267 J. Prasain 01/19/11 12 Neutral losses (162 and 180) is useful in deciding whether sugar is attached to an aromatic ring or not OH 100 HO 253 Hexose attached CH2OH HO O To the ring B HO O Possible 50 O structure 180 Da O- O 433 0 HO HO CH2OH 253 100 162 loss is an indicative Rel.
Load more

Recommended publications
  • An Introduction to Isotopic Calculations John M
    An Introduction to Isotopic Calculations John M. Hayes ([email protected]) Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA, 30 September 2004 Abstract. These notes provide an introduction to: termed isotope effects. As a result of such effects, the • Methods for the expression of isotopic abundances, natural abundances of the stable isotopes of practically • Isotopic mass balances, and all elements involved in low-temperature geochemical • Isotope effects and their consequences in open and (< 200°C) and biological processes are not precisely con- closed systems. stant. Taking carbon as an example, the range of interest is roughly 0.00998 ≤ 13F ≤ 0.01121. Within that range, Notation. Absolute abundances of isotopes are com- differences as small as 0.00001 can provide information monly reported in terms of atom percent. For example, about the source of the carbon and about processes in 13 13 12 13 atom percent C = [ C/( C + C)]100 (1) which the carbon has participated. A closely related term is the fractional abundance The delta notation. Because the interesting isotopic 13 13 fractional abundance of C ≡ F differences between natural samples usually occur at and 13F = 13C/(12C + 13C) (2) beyond the third significant figure of the isotope ratio, it has become conventional to express isotopic abundances These variables deserve attention because they provide using a differential notation. To provide a concrete the only basis for perfectly accurate mass balances. example, it is far easier to say – and to remember – that Isotope ratios are also measures of the absolute abun- the isotope ratios of samples A and B differ by one part dance of isotopes; they are usually arranged so that the per thousand than to say that sample A has 0.3663 %15N more abundant isotope appears in the denominator and sample B has 0.3659 %15N.
    [Show full text]
  • Mass Spectrometry: Quadrupole Mass Filter
    Advanced Lab, Jan. 2008 Mass Spectrometry: Quadrupole Mass Filter The mass spectrometer is essentially an instrument which can be used to measure the mass, or more correctly the mass/charge ratio, of ionized atoms or other electrically charged particles. Mass spectrometers are now used in physics, geology, chemistry, biology and medicine to determine compositions, to measure isotopic ratios, for detecting leaks in vacuum systems, and in homeland security. Mass Spectrometer Designs The first mass spectrographs were invented almost 100 years ago, by A.J. Dempster, F.W. Aston and others, and have therefore been in continuous development over a very long period. However the principle of using electric and magnetic fields to accelerate and establish the trajectories of ions inside the spectrometer according to their mass/charge ratio is common to all the different designs. The following description of Dempster’s original mass spectrograph is a simple illustration of these physical principles: The magnetic sector spectrograph PUMP F DD S S3 1 r S2 Fig. 1: Dempster’s Mass Spectrograph (1918). Atoms/molecules are first ionized by electrons emitted from the hot filament (F) and then accelerated towards the entrance slit (S1). The ions then follow a semicircular trajectory established by the Lorentz force in a uniform magnetic field. The radius of the trajectory, r, is defined by three slits (S1, S2, and S3). Ions with this selected trajectory are then detected by the detector D. How the magnetic sector mass spectrograph works: Equating the Lorentz force with the centripetal force gives: qvB = mv2/r (1) where q is the charge on the ion (usually +e), B the magnetic field, m is the mass of the ion and r the radius of the ion trajectory.
    [Show full text]
  • Good Practice Guide for Isotope Ratio Mass Spectrometry, FIRMS (2011)
    Good Practice Guide for Isotope Ratio Mass Spectrometry Good Practice Guide for Isotope Ratio Mass Spectrometry First Edition 2011 Editors Dr Jim Carter, UK Vicki Barwick, UK Contributors Dr Jim Carter, UK Dr Claire Lock, UK Acknowledgements Prof Wolfram Meier-Augenstein, UK This Guide has been produced by Dr Helen Kemp, UK members of the Steering Group of the Forensic Isotope Ratio Mass Dr Sabine Schneiders, Germany Spectrometry (FIRMS) Network. Dr Libby Stern, USA Acknowledgement of an individual does not indicate their agreement with Dr Gerard van der Peijl, Netherlands this Guide in its entirety. Production of this Guide was funded in part by the UK National Measurement System. This publication should be cited as: First edition 2011 J. F. Carter and V. J. Barwick (Eds), Good practice guide for isotope ratio mass spectrometry, FIRMS (2011). ISBN 978-0-948926-31-0 ISBN 978-0-948926-31-0 Copyright © 2011 Copyright of this document is vested in the members of the FIRMS Network. IRMS Guide 1st Ed. 2011 Preface A few decades ago, mass spectrometry (by which I mean organic MS) was considered a “black art”. Its complex and highly expensive instruments were maintained and operated by a few dedicated technicians and its output understood by only a few academics. Despite, or because, of this the data produced were amongst the “gold standard” of analytical science. In recent years a revolution occurred and MS became an affordable, easy to use and routine technique in many laboratories. Although many (rightly) applaud this popularisation, as a consequence the “black art” has been replaced by a “black box”: SAMPLES GO IN → → RESULTS COME OUT The user often has little comprehension of what goes on “under the hood” and, when “things go wrong”, the inexperienced operator can be unaware of why (or even that) the results that come out do not reflect the sample that goes in.
    [Show full text]
  • (LC-MS/MS) Method for the Determination of NDMA in Ranitidine Drug Substance and Solid Dosage Drug Product
    10/17/2019 Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Method for the Determination of NDMA in Ranitidine Drug Substance and Solid Dosage Drug Product Background: Ranitidine is a prescription and over-the-counter drug used to treat acid reflux. The drug is a histamine-2 receptor antagonist (acid inhibitor or H2 blocker). Some of the common H2 receptor blockers include: Ranitidine (Zantac), Nizatidine (Axid), Famotidine (Pepcid, Pepcid AC) and Cimetidine (Tagamet, Tagamet HB). Ranitidine medicine was suspected of being contaminated with N-nitroso-di-methylamine (NDMA), a probable human carcinogen, following notification in June 2019. Accordingly, a liquid chromatography-high resolution mass spectrometry (LC-HRMS) method was developed and validated by the Agency to determine the level of NDMA in ranitidine drug products and drug substances. This method is a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of NDMA in ranitidine drug substance and drug product. This LC-MS method based on a QQQ platform may be used as an alternative or confirmatory method for the liquid chromatography high resolution mass spectrometry (LC-HRMS) method detailed in FY19-177- DPA-S. The QQQ platform is more widely available than the LC-HRMS platform previously shared by the agency. Conclusions: An LC-MS/MS method was developed and validated following ICH Q2 (R1) for the detection and quantitation of NDMA in Ranitidine drug substance and drug product. The limit of detection (LOD), limit of quantitation (LOQ) and range of the method are summarized below: NDMA LOD (ng/mL) 0.3 (ppm) 0.01 LOQ (ng/mL) 1.0 (ppm) 0.033 Range (ng/mL) 1.0 - 100 (ppm) 0.033 – 3.33 Page 1 of 7 10/17/2019 LC-MS/MS Method for the Determination of NDMA impurity in Ranitidine Drug Substance or Solid Dosage Drug Product Purpose This method is used to quantitate N-nitroso-di-methylamine (NDMA) impurity in ranitidine drug substance or solid dosage drug product.
    [Show full text]
  • Laser-Induced Dissociation of Phosphorylated Peptides Using
    09_Cotter 10/19/07 7:57 AM Page 133 Clinical Proteomics Copyright © 2006 Humana Press Inc. All rights of any nature whatsoever are reserved. ISSN 1542-6416/06/02:133–144/$30.00 (Online) Original Article Laser-Induced Dissociation of Phosphorylated Peptides Using Matrix Assisted Laser Desorption/Ionization Tandem Time-of-Flight Mass Spectrometry Dongxia Wang,1 Philip A. Cole,2 and Robert J. Cotter2,* 1Biotechnology Core Facility, National Center for Infectious Disease, Center for Disease Control and Prevention, Atlanta, GA; 2Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD site or concensus sequence is present in a given Abstract tryptic peptide. Here, we investigated the frag- Reversible phosphorylation is one of the mentation of phosphorylated peptides under most important posttranslational modifications laser-induced dissociation (LID) using a of cellular proteins. Mass spectrometry is a MALDI-time-of-flight mass spectrometer with a widely used technique in the characterization of curved-field reflectron. Our data demonstrated phosphorylated proteins and peptides. Similar that intact fragments bearing phosphorylated to nonmodified peptides, sequence information residues were produced from all tested peptides for phosphopeptides digested from proteins can that contain at least one and up to four be obtained by tandem mass analysis using phosphorylation sites at serine, threonine, or either electrospray ionization or matrix assisted tyrosine residues. In addition, the LID of laser desorption/ionization (MALDI) mass phosphopeptides derivatized by N-terminal spectrometry. However, the facile loss of neutral sulfonation yields simplified MS/MS spectra, phosphoric acid (H3PO4) or HPO3 from precur- suggesting the combination of these two types sor ions and fragment ions hampers the precise of spectra could provide an effective approach determination of phosphorylation site, particu- to the characterization of proteins modified by larly if more than one potential phosphorylation phosphorylation.
    [Show full text]
  • Electron Ionization
    Chapter 6 Chapter 6 Electron Ionization I. Introduction ......................................................................................................317 II. Ionization Process............................................................................................317 III. Strategy for Data Interpretation......................................................................321 1. Assumptions 2. The Ionization Process IV. Types of Fragmentation Pathways.................................................................328 1. Sigma-Bond Cleavage 2. Homolytic or Radical-Site-Driven Cleavage 3. Heterolytic or Charge-Site-Driven Cleavage 4. Rearrangements A. Hydrogen-Shift Rearrangements B. Hydride-Shift Rearrangements V. Representative Fragmentations (Spectra) of Classes of Compounds.......... 344 1. Hydrocarbons A. Saturated Hydrocarbons 1) Straight-Chain Hydrocarbons 2) Branched Hydrocarbons 3) Cyclic Hydrocarbons B. Unsaturated C. Aromatic 2. Alkyl Halides 3. Oxygen-Containing Compounds A. Aliphatic Alcohols B. Aliphatic Ethers C. Aromatic Alcohols D. Cyclic Ethers E. Ketones and Aldehydes F. Aliphatic Acids and Esters G. Aromatic Acids and Esters 4. Nitrogen-Containing Compounds A. Aliphatic Amines B. Aromatic Compounds Containing Atoms of Nitrogen C. Heterocyclic Nitrogen-Containing Compounds D. Nitro Compounds E. Concluding Remarks on the Mass Spectra of Nitrogen-Containing Compounds 5. Multiple Heteroatoms or Heteroatoms and a Double Bond 6. Trimethylsilyl Derivative 7. Determining the Location of Double Bonds VI. Library
    [Show full text]
  • Modern Mass Spectrometry
    Modern Mass Spectrometry MacMillan Group Meeting 2005 Sandra Lee Key References: E. Uggerud, S. Petrie, D. K. Bohme, F. Turecek, D. Schröder, H. Schwarz, D. Plattner, T. Wyttenbach, M. T. Bowers, P. B. Armentrout, S. A. Truger, T. Junker, G. Suizdak, Mark Brönstrup. Topics in Current Chemistry: Modern Mass Spectroscopy, pp. 1-302, 225. Springer-Verlag, Berlin, 2003. Current Topics in Organic Chemistry 2003, 15, 1503-1624 1 The Basics of Mass Spectroscopy ! Purpose Mass spectrometers use the difference in mass-to-charge ratio (m/z) of ionized atoms or molecules to separate them. Therefore, mass spectroscopy allows quantitation of atoms or molecules and provides structural information by the identification of distinctive fragmentation patterns. The general operation of a mass spectrometer is: "1. " create gas-phase ions "2. " separate the ions in space or time based on their mass-to-charge ratio "3. " measure the quantity of ions of each mass-to-charge ratio Ionization sources ! Instrumentation Chemical Ionisation (CI) Atmospheric Pressure CI!(APCI) Electron Impact!(EI) Electrospray Ionization!(ESI) SORTING DETECTION IONIZATION OF IONS OF IONS Fast Atom Bombardment (FAB) Field Desorption/Field Ionisation (FD/FI) Matrix Assisted Laser Desorption gaseous mass ion Ionisation!(MALDI) ion source analyzer transducer Thermospray Ionisation (TI) Analyzers quadrupoles vacuum signal Time-of-Flight (TOF) pump processor magnetic sectors 10-5– 10-8 torr Fourier transform and quadrupole ion traps inlet Detectors mass electron multiplier spectrum Faraday cup Ionization Sources: Classical Methods ! Electron Impact Ionization A beam of electrons passes through a gas-phase sample and collides with neutral analyte molcules (M) to produce a positively charged ion or a fragment ion.
    [Show full text]
  • Find the Molar Mass of Sodium Carbonate, Na 2CO3. Na 2 X
    Moles and Molar Mass The mole is the "counting unit" used by chemists to indicate the number of atoms, ions, molecules, or formula units present in a particular chemical sample. The mole is similar to other counting units that you've used before....pair (2), dozen (12), and gross (144). One mole of a compound contains Avogadro's number (6.022 x 1023) of molecules (molecular compound) or formula units (ionic compound). The molar mass of a compound tells you the mass of 1 mole of that substance. In other words, it tells you the number of grams per mole of a compound. The units for molar mass are, therefore, grams/mole. To find the molar mass of a compound: 1. Use the chemical formula to determine the number of each type of atom present in the compound. 2. Multiply the atomic weight (from the periodic table) of each element by the number of atoms of that element present in the compound. 3. Add it all together and put units of grams/mole after the number. Example: Find the molar mass of sodium carbonate, Na2CO3. Na 2 x 23.0 = 46.0 C 1 x 12.0 = 12.0 O 3 x 16.0 = 48.0 molar = 106.0 g/mole mass For many (but not all) problems, you can simply round the atomic weights and the molar mass to the nearest 0.1 g/mole. HOWEVER, make sure that you use at least as many significant figures in your molar mass as the measurement with the fewest significant figures.
    [Show full text]
  • Fundamentals of Biological Mass Spectrometry and Proteomics
    Fundamentals of Biological Mass Spectrometry and Proteomics Steve Carr Broad Institute of MIT and Harvard Modern Mass Spectrometer (MS) Systems Orbitrap Q-Exactive Triple Quadrupole Discovery/Global Experiments Targeted MS MS systems used for proteomics have 4 tasks: • Create ions from analyte molecules • Separate the ions based on charge and mass • Detect ions and determine their mass-to-charge • Select and fragment ions of interest to provide structural information (MS/MS) Electrospray MS: ease of coupling to liquid-based separation methods has made it the key technology in proteomics Possible Sample Inlets Syringe Pump Sample Injection Loop Liquid Autosampler, HPLC Capillary Electrophoresis Expansion of the Ion Formation and Sampling Regions Nitrogen Drying Gas Electrospray Atmosphere Vacuum Needle 3- 5 kV Liquid Nebulizing Gas Droplets Ions Containing Solvated Ions Isotopes Most elements have more than one stable isotope. For example, most carbon atoms have a mass of 12 Da, but in nature, 1.1% of C atoms have an extra neutron, making their mass 13 Da. Why do we care? Mass spectrometers “see” the isotope peaks provided the resolution is high enough. If an MS instrument has resolution high enough to resolve these isotopes, better mass accuracy is achieved. Stable isotopes of most abundant elements of peptides Element Mass Abundance H 1.0078 99.985% 2.0141 0.015 C 12.0000 98.89 13.0034 1.11 N 14.0031 99.64 15.0001 0.36 O 15.9949 99.76 16.9991 0.04 17.9992 0.20 Monoisotopic mass and isotopes We use instruments that resolve the isotopes enabling us to accurately measure the monoisotopic mass MonoisotopicMonoisotopic mass; all 12C, mass no 13C atoms corresponds to 13 lowestOne massC atom peak Two 13C atoms Angiotensin I (MW = 1295.6) (M+H)+ = C62 H90 N17 O14 TheWhen monoisotopic the isotopes mass of aare molecule clearly is the resolved sum of the the accurate monoisotopic masses for the massmost abundant isotope of each element present.
    [Show full text]
  • An Introduction to Mass Spectrometry
    An Introduction to Mass Spectrometry by Scott E. Van Bramer Widener University Department of Chemistry One University Place Chester, PA 19013 [email protected] http://science.widener.edu/~svanbram revised: September 2, 1998 © Copyright 1997 TABLE OF CONTENTS INTRODUCTION ........................................................... 4 SAMPLE INTRODUCTION ....................................................5 Direct Vapor Inlet .......................................................5 Gas Chromatography.....................................................5 Liquid Chromatography...................................................6 Direct Insertion Probe ....................................................6 Direct Ionization of Sample ................................................6 IONIZATION TECHNIQUES...................................................6 Electron Ionization .......................................................7 Chemical Ionization ..................................................... 9 Fast Atom Bombardment and Secondary Ion Mass Spectrometry .................10 Atmospheric Pressure Ionization and Electrospray Ionization ....................11 Matrix Assisted Laser Desorption/Ionization ................................ 13 Other Ionization Methods ................................................13 Self-Test #1 ...........................................................14 MASS ANALYZERS .........................................................14 Quadrupole ............................................................15
    [Show full text]
  • An Organic Chemist's Guide to Electrospray Mass Spectrometric
    molecules Review An Organic Chemist’s Guide to Electrospray Mass Spectrometric Structure Elucidation Arnold Steckel 1 and Gitta Schlosser 2,* 1 Hevesy György PhD School of Chemistry, ELTE Eötvös Loránd University, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary; [email protected] 2 Department of Analytical Chemistry, ELTE Eötvös Loránd University, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary * Correspondence: [email protected] Received: 16 January 2019; Accepted: 8 February 2019; Published: 10 February 2019 Abstract: Tandem mass spectrometry is an important tool for structure elucidation of natural and synthetic organic products. Fragmentation of odd electron ions (OE+) generated by electron ionization (EI) was extensively studied in the last few decades, however there are only a few systematic reviews available concerning the fragmentation of even-electron ions (EE+/EE−) produced by the currently most common ionization techniques, electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). This review summarizes the most important features of tandem mass spectra generated by collision-induced dissociation fragmentation and presents didactic examples for the unexperienced users. Keywords: tandem mass spectrometry; MS/MS fragmentation; collision-induced dissociation; CID; ESI; structure elucidation 1. Introduction Electron ionization (EI), a hard ionization technique, is the method of choice for analyses of small (<1000 Da), nonpolar, volatile compounds. As its name implies, the technique involves ionization by electrons with ~70 eV energy. This energy is high enough to yield very reproducible mass spectra with a large number of fragments. However, these spectra frequently lack the radical type molecular ions (M+) due to the high internal energy transferred to the precursors [1].
    [Show full text]
  • Methods of Ion Generation
    Chem. Rev. 2001, 101, 361−375 361 Methods of Ion Generation Marvin L. Vestal PE Biosystems, Framingham, Massachusetts 01701 Received May 24, 2000 Contents I. Introduction 361 II. Atomic Ions 362 A. Thermal Ionization 362 B. Spark Source 362 C. Plasma Sources 362 D. Glow Discharge 362 E. Inductively Coupled Plasma (ICP) 363 III. Molecular Ions from Volatile Samples. 364 A. Electron Ionization (EI) 364 B. Chemical Ionization (CI) 365 C. Photoionization (PI) 367 D. Field Ionization (FI) 367 IV. Molecular Ions from Nonvolatile Samples 367 Marvin L. Vestal received his B.S. and M.S. degrees, 1958 and 1960, A. Spray Techniques 367 respectively, in Engineering Sciences from Purdue Univesity, Layfayette, IN. In 1975 he received his Ph.D. degree in Chemical Physics from the B. Electrospray 367 University of Utah, Salt Lake City. From 1958 to 1960 he was a Scientist C. Desorption from Surfaces 369 at Johnston Laboratories, Inc., in Layfayette, IN. From 1960 to 1967 he D. High-Energy Particle Impact 369 became Senior Scientist at Johnston Laboratories, Inc., in Baltimore, MD. E. Low-Energy Particle Impact 370 From 1960 to 1962 he was a Graduate Student in the Department of Physics at John Hopkins University. From 1967 to 1970 he was Vice F. Low-Energy Impact with Liquid Surfaces 371 President at Scientific Research Instruments, Corp. in Baltimore, MD. From G. Flow FAB 371 1970 to 1975 he was a Graduate Student and Research Instructor at the H. Laser Ionization−MALDI 371 University of Utah, Salt Lake City. From 1976 to 1981 he became I.
    [Show full text]