1451
Anal. Chem. lB86, 58, 1451-1453
by using AAS, with good agreement. The results obtained are depicted in Tables 11-V. A preliminary step in the determination of zinc in biological samples is the destruction of the organic matter. We have chosen the wet oxidation method described by Bajo (25),in which a mixture of concentrated nitric acid and HzOzis used. Registry No. Zn, 7440-66-6; salicylaldehyde thiocarbohydrazone, 41361-11-9; aluminum alloy (20b), 101248-16-2;lead concentrate (X), 101315-79-1;white metal @e), 101315-80-4.
LITERATURE CITED (1) Falchuk, K. H. N. N. Engl. J . M e d . 1977, 296, 1129. (2) Trace Elements ln Human Health and Disease; Prasad, A. S., Oberlease, D., Eds.; Academlc Press: London, 1976; Vol. 1, Zinc and Copper. (3) Giroux, E. L.; Durleux, M.; Schechter, P. J. Bloinorg. Chem. 1978, 5 , 211. (4) Lafargue, P.; Couture, J. C.; Monteil, R.; Guilband, J.; Saliou, L. Clln. Chlm. Acta 1978, 66, 181. (5) Allah, P.; Foussard, E.; Boyer, J. Clin. Chlm. Acta 1977, 7 8 , 183. (6) Foote, J. W.; Delves, H. T. Analyst(London) 1982, 707, 121. (7) Foote, J. W.; Delves, H. T. Analyst(London) 1982, 707, 1229. (8) Brown, A. A,; Taylor, A. Analyst (London) 1984, 709, 1455. (9) Gardiner, P. F.; Ottaway, J. M. Anal. Chim. Acta 1981, 124, 281. (IO) Parr, R. M.; Taylor, D. M. Blocbem. J. 1984, 97. 424.
(11) Magglore Glovannetti, Q.;Malvano, R. I n Nuclear Actlvation Techniques In the Life Sciences: International Atomic Energy Agency: VIenna, 1967; p 511. (12) Frltze, K.; Robertson, R. J. Radloanal. Cbem. 1988, 7 , 463. (13) de la Cruz, B. I n Trace Elements in Relatlon to Cardiovascular Disease s ; International Atomic Enery Agency: Vienna, 1973; p 19. (14) . . Versieck. J.; Barbier, F.; Speecke, A,; Hoste, J. Clin. Chem. (Winston-Salem, N.C.)1974, 2 0 , 141. (15) Behne, D.; Jurgensen, H. J. Radioanal. Chem. 1978, 42. 447. (16) Vallee, B. L.; Glbson, J. G.J. Blol. Cbem. 1948, 776, 445. (17) Koch, H. J.; Smith, E. R.; Shimp, N. F.; Connor, J. Cancer 1958, 9, 499. (18) Heirlng, W. 6.; Leavell, B. S.; Paixao, L. M.; Yoe, J. H. Am. J. Ciin. Nutr. 1980, 8 , 846. (19) Palxao, L. M.; Yoe, J. H. Clln. Cblm. Acta 1959, 4 , 507. (20) Monacelli, R.; Tanaka H.; Yoe, J. H. Clin. Chim. Acta 1958, 7 , 577. (21) Nledermeier, W.; Crlggs, J. H. J. Chronic Dis. 1971, 23, 527. (22) Stump, I. 0.: Carruthers, J.; D'Auria, J. M.; Applegarth, D. A.; Davidson, A. G. F. Clln. Biochem. 1977, 70, 127. (23) MontafiaGonzBlez, M. T.; Gomez Ariza, J. L.; Gar& de Torres, A. Anal. Quim. 1984, 8 0 , 129. (24) Youden, W. J.; Statistical Methods for Chemist; Wiley: New York, 1951. (25) Bajo, S.; Suter, U.; Aeschllman, B. Anal. Chim. Acta 1983, 749, 321.
RECEIVED for review November 4, 1985. Accepted February 5 , 1986.
Extractive Spectrophotometric Method for the Determination of Vanadium(V) in Steels and Titanium Base Alloy Anjaneyulu Yerramilli,* C. S. Kavipurapu, R. R. Manda, and C. M. Pillutla Department of Chemistry, Nagarjuna University, Nagarjunanagar, Andhra Pradesh, India 522 510
Vanadium(V) forms enionlc chelates with 4-(2-pyrldylazo)resorcinol (PAR) at pH 5.0-7.8, which can be quantltatlvely extracted Into nltrobensene as an ion pair with xylometaroionium cation (XMH). The ternary system has an absorption maximum at 540 nm and obeys Beer's law in the range 0-1.8 pg of vanadlum/mL with a molar absorptivity 4.56 X I O 4 L mol-' cm-'. The Job's method of contlnuous variations Indicated a composition of 1:1:1 for vanadium: PAR:XMH for the extractlng species. I n the presence of 1,2-dlaminocyciohexanetetraacetic acid as a masking agent, the extraction becomes highly selective, and this method can be applied for the determination of vanadlum(V), in the presence of varlous metal ions in synthetlc mixtures, in steels, and In tltanium base alloy.
Vanadium(V) reacts with 4- (2-pyridylaza)resorcinol (PAR) producing intensely colored water-soluble anionic complexes (1-7), which serves as a basis for the spectrophotometric determination of vanadium. The extraction of [4-(2pyridylazo)resorcinolato]vanadium(V) (V02L-) anionic complex paired with quaternary ammonium cations like tetraphenylphosphonium chloride, tetraphenylarsonium chloride, tetradecyldimethylbenzylammonium chloride, trioctylmethylammonium chloride, and with trioctylphosphine oxide has been ivestigated by several workers (8-12). However, in many of these extraction spectrophotometric procedures difficulties arise due to the delay in the separation of the two phases and significant absorbance for the reagent blank solution, particularly when concentrated solutions of reagents are used. 0003-2700/86/0358-145 1$01.50/0
In our investigations we have observed that the 1:l vanadium-PAR complex can be selectively extracted with xylometazolonium cation (XMH) in the presence of 1,2-diaminocyclohexanetetraacetic acid (CyDTA), which has been exploited for rapid and selective spectrophotometric methods for the determination of vanadium in steels and titanium base alloy, and these results are presented in this paper. The present method has many advantages over the other spectrophotometric methods for vanadium. It has high sensitivity, and the interference from many diverse ions can be completely masked with CyDTA. The molar absorptivity of the present method is found to be 4.56 X lo4 L mol-l cm-l, which is higher than those reported earlier for vanadium with phosphotungstic acid ( E = 2000) (13),xylenol orange (e = 13000) (14-16),pyrocatechol violet ( t = 36800) (In,142pyridylazo)-2-naphthol (PAN) in CHC13 (e = 16900) (18),PAN and ~-[(6-methyl-2-pyridyl)azo]-2-hydroxynaphthalene Noxide in CHC13 ( t = 16000) (19),PAR in aqueous medium ( E = 36 OOO) (20), PAR and benzyldimethyltetradecylammonium cation (t = 33500), or trioctylphosphine oxide ( 6 = 14000) (12) in CHCIS. Further, with XMH as the countercation, clear separation of the phases can be achieved immediately and there is no difficulty in the separation of phases even with high reagent concentrations. The reagent blank solutions do not show any absorbance, and the system can be best extracted over a wide pH range.
EXPERIMENTAL SECTION Apparatus. Absorbance measurements are made with a Systronics digital spectrophotometer Model 106 MK (11). pH measurements are made on an Elico expanded pH meter Model 335. 0 1986 American Chemical Society
1452
ANALYTICAL CHEMISTRY, VOL. 58, NO. 7, JUNE 1986
Table I. Determination of Vanadium in Steels and Titanium Base Alloys 70 vanadium certified value foundn std dev
sample and sample type (A) high-speed steel (i) BCS no. 220/1 (ii) BCS no. 241/1 (iii) BCS no. 241/2 (iv) BCS no. 484 (B) chromium-vanadium steel (i) BCS no. 224/1 (ii) BCS no. 405 (C) titanium base alloy (i) AI-V (64)
2.09 1.57 1.59 0.94
2.093 1.572 1.582 0.942
0.02
0.19 0.32
0.190 0.318
0.02
4.10
4.042
0.08
0.01
0.03 0.02
0.01
" Average of six determinations. Reagents. Vanadium (V) Stock Solution. A 0.01 M solution was standardized by titration with a standard EDTA solution. 4-(2-Pyridylazo)resorcino1Stock Solution. A 0.01 M solution is prepared by dissolving the compound (Reidel) crystallized twice from a 1:l ethanol-water mixtures in demineralized water. The purity is checked by spectrophotometric titrations (21). Xylometazoline hydrochloride (XMH). A 0.01 M solution is prepared from pure sample (Fairdeal Corp., Bombay) and kept in an amber bottle.
