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REVIEW OF SPECTROPHOTOMETRIC METHODS FOR DETERMINATION OF VANADIUM Behrooz Rezaie, Raziya Zabeen, A.K. Goswami and D.N. Purohit Department o f Chemistry M .L Sukhadia University Udaipur - 313 001, Rajasthan (India) CONTENTS Page REVIEW ................................... ......................................... 1 REFERENCES ...................................................................... 200 REVIEW A survey of literature reported for spectrophotometric determination of vanadium from 1973 to 1991 has been made. To save space the available information has been reported in tabular form. The condensed information is presented under the following headings: name of the reagent, X or working wavelength with e, optimum pH, remarks and references. Under "remarks* information regarding composition of the complex, details of the method, interferences, application of the method, etc., are reported. Shortly before this survey was completed, a review was published (reference 430), covering a significant part of the subject (hydroxamic acid complexes) as studied between 1963 and 1988. There will therefore be some unavoidable overlapping between both reviews. 1 Name of the Reagent X or pH Remarks Refs. working wavelength withe 5 -Dimethylamino-1 - 595 nm 3 J Vanadium forms a (1:1) complex with the re- 1 (2-thiazolylazo) «=42000 to agent and is extracted into CHC13 from aq. phenol 43 medium. Beer’s law is obeyed with up to 1.2 p.g of vol. per mL Interference in the determination of V is caused by Ti(IV), Zr, Nb, Fe(III) and oxalate, but Nb and Fe(III) can be masked with KCN and triethanolamine, respectively. Procedure: To a portion of test soin, containing <10 /tg of V is added 1 ml of 0.01% methanolic reagent, the soin, is adjusted to pH 4 with Na acetate-HO buffer and diluted to 50 ml with HgO and after 15 min. the V complex is extracted into 25 ml of CHClg. The extinction is measured vs. reagent blank extract. To determine V in carbon steel most of the Fe is extracted from the sample with isobutyl ketone. The aq. phase is treated with H2S04 and diluted to 500 ml with H O, then a portion is treated with 2 ml of 0.5% KCN soin, and determination is com pleted as described above. For steel containing 0.1% of V, the coefficient of variation was 1%. Antbanilic acid S2S nm 0.2 In aq. ethanolic HgS 04 (pH 0.2 to N in acid), 2 isopropylidene- e = 5100 to V(V) forms a yellow 1:2 complex with the reagent hydrazide Nacid in at least 100-fold amount. The complex becomes cherry-red on addition of acetons in any propor tion between 1:4 and 4:1 of original soln. volume, but extinction remains constant Beer's law is obeyed for 3 to 100 /ig of V per 25 mL There is no interference from 10,000 fold amount of A1 or al kali, alkaline-earth or rare earth metals, 500-fold amount of H , Zr, Sc, Zn, Mn, Ga, Ge, or Cr, 200- fold amounts of U, Th, Nb, Ta, Cd, Fe, Cu, Co or W o r 3500-fold amounts of Mo, or In, but Os and BrOa must be absent. To determine V in silicates, the sample (1 g. containing down to 6.5 ppm of V) is dissolved in HNOg- H a (1:3) in the presence of aq. HaOa, the soln. is filtered through paper pulp, and the residue is washed with 1% HNO. and the 3 hot filtrate is treated with aq. NHg in slight excess. The ppt. is collected and washed with 1% NH^NOg soln. and dissolved in 50 ml of N-H SO. and 10 ml of soln. is treated with 1.5 ml of H3P 04 and then oxidised with 0.5% KMNO^ soln.; unconsumed KMN04 is decomposed with 0.05% of reagent in acetone, is added, the mixture is diluted to 25 ml with acetone and its extinction is measured. The calibration graph covers the range up to 10 of V. Name of the Reagent X or Remarks Refs. m ax. PH working wavelength withe 3-Hydroxy-l-3-diphenyl All complexes are yellow-green and their compo 3 triazene and its sition (reagenfcmetal) is 1:1. All are water soluble derivatives except the first (a) which is soluble in water- ethanol. ■ - i a) 3-Hydroxy-l,3- 410 nm 3.1 Beer’s law is obeyed in the range of 0.25 to 10 diphenyl triazene «=5875 to ppm. The value of Sandell’s sensitivity is 0.085 4.2 jig/cm2. b) 3-Hydroxy-3-phenyl 400 nm 3 3 Beer’s law is obeyed from 0.25 to 10 ppm. The 2 -1-p-sulphonato- «=5875 to value of Sandells’ sensitivity is 0.0085 /tg/cm . phenyltriazene 4 3 (Na. salt) c) 3-Hydroxy-3-phenyl 400 nm 3 3 Beer’s law is obeyed in the range 0.25 to 10 -1-o-sulphonato to ppm. The value of Sandell’s sensitivity is 0.026 phenyltriazene 43 /tg/cm2. (Na. salt) d) 3-Hydroxy-3-phenyl 400 nm 3.6 Beer’s law is obeyed in the range 0.25 to 12 -1-m-sulphonato «=5250 to ppm. The value of Sandell’s sensitivity is phenyltriazene 4.6 0.0095 /xg.cm2. (Na. salt). e) 3-Hydrc*y-3-phenyl 410 nm 3.6 Beer’s law is obeyed in the range 0.25 to 12 -l-(4-sulphonato- to ppm. The value of Sandell’s sensitivity is 0.05 6-methyl phenyl) 4.6 /¿g/cm2. triazene (Na. salt) f) 3-Hydroxy-3-phenyl 400 nm 3.0 Beer’s law is obeyed in the range 0.1 to 8.0 -l-(4-sulphonato-5- «=6625 to ppm. The value of Sandell’s sensitivity is methylphenyl 4.4 0.0075 Mg/cm2. triazene (Na. salt). Oxalate, F\ Fe(III), Pd(II), M oO^II), Cr(III) and H(IV) interfere seriously. The fodowing could be tolerated up to the tolerance limit in ppm (given in parentheses): Ni2+ (50); Co2+ (10); MnZ+ (10); WO 2 (20); UO 2* (10); La3+ (30); Ce3+ (20); Zn2+ (100); Cd2* (200); Hg2+ (100); As3+ (100) and Th4+ (40). Cu(II) could be tolerated up to 50 ppm only in presence of Na thiosulphate soln. (1%). U +, Na+, K +, Br', I', Cl', P O ^ , boric arid, citrate and tartrate did not interfere. Pyrogallo! 610 nm 6-5 At pH 6.5 (610 nm) Beer’s law is obeyed up to 200 « = 7630 /tg of V(V) in 50 ml of soln.. There is no interfer 410 nm ence from up to 1 mg of Pd, Ni, Co(U), Sr, Sn(II), « = 4760 Ba, Mn(Il), Mg, Zn or Be or up to 5 mg of Al. The reagent has also been used for determination of u* Ti(IV) and Fe(III) separately and collectively. Name of the Reagent \ or Remarks Refs. m ax. PH working wavelength withe V(IV) (0.5 to 3.5 ppm) reduces the reagent to its 5 Ferriin [Tris (1,10, 510 nm H 2S ° 4 phenanthroline) medium Fe(II) analogue ferroin in a medium of HgS04 Iron (III)] containing acetic acid to accelerate the reaction, and the extinction of the ferroin is measured. The error is <2%. There is no interference from up to 1 mg of Mn(II), Al, Cd, Co, Mg, Pd(II), Cr(ill), Na, K, or U(\h), up to 50 mg of citrate, Cl’ or acetate or up to 25 mg of PC>4 . Excess of free l,10,phenanthro!ine stabilises the ferroin soln. and particularly eli-minates interference from Cu(II), Ni and Zn. 1^3-Phenyloxy 560 nm Acetic The reagent gives a blue violet ppL with vana- 6 amidine [N-hydroxy- add date ion in acetic add medium and is quantita NN’-diphenyl medium tively extracted into CHClg. The absorption benzamidine] max. of the vanadium complex is at 550 to 575 nm and that of the reagent is at 315 nm. The system obeys Beer’s law in the range of 2.4 to 8.8 ppm of V, and sensitivity is 0.011 /tg/cm’2. There is no interference from Fe(II), Mo(VI). Cr(III), Mn(II), Cu(II), Ni(II), Sb(III), or ASC>4 , but Ti(IV) or W(VI) interfere. The result of V determination in two standard steels agreed with the certified value. Butanol and PAR 545 nrn The test soln. containing up to 20 /rg of V(V), 7 [4-(2-pyridyIazo) is adjusted to pH 3 by adding 1 ml of 0.01M- resorcinol] HNC>3, then diluted to 10 ml with HgO and shaken for 5 min. with 10 ml of 5M-butanol in benzene to extract the V(V). The organic phase is shaken for 5 min. with 10 ml of back-extraction soln. (comprising 5 ml of phosphate buffer soln. of pH 6.4, 2 ml of 0.1% PAR soln. and HgO), and the extinction of the resulting aq. phase is measured vs. HgO. Beer’s law is obeyed over the cited range, and the Sandell sensitivity is 0.0020 ¿ig/cm'2. Slight interference is caused by Co and W(V1), but V(V) is separated from Cr(VI) by this method. The method is used to determine V in rocks (e.g. 23 ppm in granodiorite and 178 ppm in basalt. N-p-ToIyl-2- 540 nm The 1:2 complex was extracted into CHC13 from 6 8 furohydroxamic acid «=3000 to 8 M-HC1 medium, and its absorbance was measured. Beer’s law is obeyed in the range 0 to 15 ftg of V in the organic phase (25 ml).

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