dividual results and a recovery of &5% for the sum of the acids. T h e present method was applied to the study of the deiodination products of 1311-labeled o-iodobenzoic acid produced by radiolysis under the influence of different catalysts. I t is known t h a t benzoic and hydroxybenzoic acids are among the products of this radiolytic deiodination. T h e extent of deiodination was determined by measuring the radioactive iodide originating from t h e labeled acid. T h e interference of the unreacted iodobenzoic acid with the ahsorhance measurements was estimated as follows. T h e absorption coefficients of iodobenzoic acid were determined a t 300, 260, and 225 nm. T h e following values were ohtained: t = 720 a t 300 nm; 1140 at 260 n m and 10 000 a t 225 nm. Before applying t h e method for the calculation of o-, m-, p - hydroxybenzoic acids and benzoic acid, as described above, the absorbances corresponding to the concentration of the unreacted iodohenzoic acid, were deduced from the total readings a t the respective wavelengths. T h e same solutions were also analyzed by paper chromatography ( I ) ; very good agreement was found between the two methods.
tives. T h e advantages of the method are its simplicity and rapidity. T h e procedure consists essentially of four spectrophotometric readings which can he carried out in about 40 minutes.
LITERATURE CITED (1) M. Mantel and E. Kushnir, J. Chromatogr., 17, 624 (1965). (2) N. E . Skelly and W. E. Crummett, Anal. Chem., 11, 1681 (1963). (3) Wataru Funasaka, Kaseimi Fujimura, and Sue Kushida, J. Chromatogr.. 64, 95 (1972). (4) E . Ludwig and U. Freirnuth, Nahrung, 9, 751 (1966). (5) S. Y. Pinella. A. D. Falco, and G. Schwartman, J. Assoc. Off. Agric. Chem., 49, 829 (1966). (6) J. E . Sinsheirner and G. 0. Breault, J. Pharm. Sci., 60, 255 (1971). (7) E. R. Blakiey. Anal. Biochem., 15, 350 (1966). (8) C. M. Williams, Anal. Biochem., 11, 224 (1965). (9) L. Lang, Ed., "Absorption Spectra in the Ultraviolet and Visible Region," Academic Press, New York, 1961. (10) A. C. Kelly, J. Pharm. Sci., 59, 1053 (1970). (11) F. D. Sneli and C. Snell. "Colorimetric Methods of Analysis," 1949, 3rd ed., Van Nostrand, London. (12) C. Bertin-Batsch, Ann. Chim., 7, 481 (1952). (13) R. 0. Scott, Analyst(London), 66, 142 (1941). (14) V. Das Gupta, J. Pharm. Sci., 61, 1625 (1972).
CONCLUSION A method is described for the simultaneous determination of benzoic acid and its three isomeric hydroxy deriva-
RECEIVEDfor review September 8, 1975. Accepted December 8,1975.
Extraction and Spectrophotometric Determination of Vanadium(V) with N-[p-N,N-Dimethylani Iino)-3-methoxy-2naphtho]hydroxamic Acid Shahid Abbas Abbasi Deparfment of Chemistry, lndian lnstitute of Technology, Bombay-400 076, lndia
On the basis of available information on the methods of determination of vanadium(V) by hydroxamic acids, the title reagent was modeled and developed as a selective and sensitive reagent for vanadium(V). The chloroform solutions of the reagent extract vanadium rapidly (5 2 min) from 2-6 M hydrochloric acid solutions as a violet complex which is measurable spectrophotometrically at 570 nm ( E = 1.2 X lo4 1. mol-' cm-'). The color system which contained vanadium and the reagent in the molar ratio 1:2, obeys Beer's law in the range 0.15-8.5 ppm of vanadium. The method of determination has a maximum standard deviation of f0.02 and tolerates the presence of several milligrams of 50 foreign ions. Vanadium was determined in ilmenite, rock phosphate, and steels.
+
N-Phenylhenzohydroxamic acid (PBHA) has been extensively used in analytical chemistry (1-3) as a reagent which is fairly sensitive and selective for the liquid-liquid extraction and spectrophotometric determination of vanadium(V). T h e advantage with PBHA is t h a t its vanadium complex attains maximum color intensity ( 6 = 4650) ( I ) in highly acidic (2.8-4.3 M HC1) solutions and can he readily extracted into various organic solvents such as chloroform, benzene, and carbon tetrachloride. T h e quickness and convenience of the PBHA method ( I ) has prompted many a t tempts to find analogues of PBHA which are more sensitive and selective reagents for vanadium than PBHA, note714
ANALYTICAL CHEMISTRY, VOL. 48, NO. 4, APRIL 1976
worthy among them being N-p-tolyl-2-thenohydroxamic acid ( t = 5700 in CHC13)(4), N-phenylcinnamohydroxamic acid ( e = 6300 in CHC13)(5) and N-phenyl-3-styrylacrylohydroxamic acid ( t = 7500 in CHC13)(6). Various claims of improved selectivity are made with the above-mentioned reagents. T h e N-phenyl-2-naphthohydroxamicacid proposed recently ( 7 ) does not appear to be a significant imacid if provement over AJ-phenyl-3-styrylacrylohydroxamic judged by the sensitivities and tolerance limits of the methods using the two respective acids. From an extensive literature search on the sensitivities and selectivities of various hydroxamic acid methods ( I , 4-13), it was noticed that the presence of strong electrondonating substituents in the para position of the N-phenyl fragment of PBHA, an increase in conjugation a t the henzo site and introduction of electron-donating groups ortho to the functional -C=O group helps in enhancing the sensitivity and selectivity of a hydroxamic acid towards vanadium(V) relative to PBHA (I). T h e studies of Cassidy and
Table I. Effect of Acidity on the Visible Absorption Spectrum of the Vanadium(V)-DAMNHA System in Chloroform Wa\elength of C o n c n of a c i d , 1\1
C(11or o f
5.00 3.00
‘L 0 450
500
550
- WAVELENGTH
600
650
-
Figure 1. Absorption spectrum of vanadium-DAMNHA system in c h l o r o f o r m vs. reagent blank
Ryan ( 1 4 ) had revealed t h a t there is a limit t o t h e introduction of T systems to t h e functional groups of hydroxamic acids as there is a loss of the complete coplanarity of the aromatic rings with t h e metal chelate ring. With all t h e known analogues of PBHA in view, a model reagent with t h e N,N-dimethyl amino group a t p-phenyl position and 3-methoxy-2-naphtho group instead of the benzo fragment (11) was conceived. T h e modeled reagent N - [p-N,,V-dimethylanilino)-3-methoxy-2-naphtho]hydroxamic acid (DAMNHA) was then synthesized and studied in detail as a reagent for extraction and determination of vanadium(\.:). It was observed that DAMNHA gives an intense violet colored complex with vanadium(V) in strongly acidic (2-6 M HC1) solutions. T h e complex is selectively extracted in various organic solvents including carbon tetrachloride, 1.2 X lo4 a t 5iO nm). Oxybenzene, and chloroform ( t genated solvents like n-butanol and isobutyl methyl ketone extract the complex more rapidly than non-oxygenated solvents but t h e sensitivity of t h e color is diminished in these solvents. T h e sensitivity and selectivity of DAMNHA for vanadium(V) are conspicuously higher than t h a t of any other P B H A analogue reported hitherto. T h e effects of various parameters such as acidity, reagent concentration, time of equilibration, diverse ions, etc. on the extractive determination of vanadium with DAMNHA are discussed below. Applications of DAMNHA in the analysis of vanadiu m in minerals and alloy steel are presented. EXPERIMENTAL Apparatus. A radiometer p H meter model PHM-29 (Hungary) was used for p H adjustments. T h e absorption spectra were recorded on a Perkin-Elmer 492-5000 spectrophotometer and measurements a t constant wavelengths were performed on a SF-4, singlebeam spectrophotometer (USSR) using matched quartz cells. Corning glass stills were used throughout. Reagent and Solutions. DAMNHA was prepared in pure form from p-nitro-.V,aV-dimethylaniline and 3-methoxy-2-naphthoic acid as detailed elsewhere ( 1 5 ) . A 0.1 hl solution of reagent in ethanol-free CHC1:3 was used for extraction work. Deionized water was employed for all purposes. T h e aqueous vanadium solution was prepared from AR ammonium metavanadate and it was standardized for vanadium content volumetrically using potassium permanganate solution ( 1 6 ) . Extraction of Vanadium(V). A 5-ml aliquot of vanadium(\.’) M )was taken in a 100-ml separatory solution ( 5 X lo-% X funnel followed by 5 ml of hydrochloric acid (4-10 M )and 5 ml of reagent solution (0.1-0.01 M). T h e contents were equilibrated for 5 min and t h e phases were allowed t o separate. T h e organic phase was tapped off, dried over anhydrous sodium sulfate, and collected in a 25-ml volumetric flask, retaining the aqueous phase which was extracted again with another 5-ml portion of reagent solution to ensure complete recovery of vanadium(\’). T h e second extract was removed, dried, and added to the first; and the contents of the separatory funnel and t h e used sodium sulfate were washed to remove any trapped drops of the organic phase. T h e washings were added to the extract in the volumetric flask which was made up to t h e
2.00 1.00 0.10
0.05
maximum
db-
c hloro for rn extract
sorption. n m
I n t e n s e violet I n t e n s e violet I n t e n s e violet R e d d i s h violet R e d d i s h violet Pinkish r e d
570 570 570 535 530 500
Molar ahsorptivity, E
12000 12000
12000
9000 8500 7500
_____
Table 11. Effect of pH on the Extraction of Vanadium(V) with DAMNHA PH
1 (Tables I and 11). Hydrochloric acid has a n advantage over sulfuric acid in that its lesser heat of dilution causes a lower temperature rise during t h e adjustment of acidity prior t o extraction, while concentrated HNO:{tends to attack the reagent. T h e color sensitivity also is adversely affected if extractions are done from sulfuric acid or nitric acid solutions. Scrubbing of such extracts with 3-6 M hydrochloric acid restores the color intensity as described ANALYTICAL CHEMISTRY, VOL. 48, NO. 4 , APRIL 1976
715
4 0.8
Table 111. Tolerance Limits of Extractive-Determination of 45 p g / 2 5 ml of Vanadium(V) with DAMNHA
I
Tolerance limit, ! 4 2 5 ml
Ions tolerated
120 000
Ag+, L i t , Na+, K + , R b + , Be*+,MgzC,Ca2+, Ba”, Sr2+,Ni2+,ZnZt, Cd2’, UO,’+,Allt, Ga3+,Th“, As3+, Sb”, Bi3+,fluoride, chloride, bromide, iodide, cyanide, phosphate Cu2+,Co’+, Mn’+, Zn2+,Pbz+,Hg2+,In3+, S n 4 + ,citrate, tartarate, ascorbate Cr3+,Fe3+,T i 3 + ,sulfate, borate PdZ+,Ti4+,Zr4+,Hf4+,molybdate, tungstate, nitrate, EDTA Pt(1V) Ir(1V)
100 000 I
L
0
4 6 MOLES LIGAND PERMOLE VANADIUM
2
-
0
Flgure 2. Job’s plots of extractions of vanadium-DAMNHA system
80 000 50 000
3 000 1 500
f r o m 4 M hydrochloric acid
Table IV. Analytical Data on Extraction of Vanadium(V) with DAMNHA Vanadium(V) f i g / 2 5 ml of extract
i T 570 nm ST 500 nrn 4T
650 nrn
MOL. E FRACTION VAN A D IUM
2.00 4.00 8.00
4.01 8.00
32.00
32.02
40.00 56.00
40.01
716
ANALYTICAL CHEMISTRY, VOL. 48, NO. 4 , APRIL 1976
1.99
56.03
1 0 deter-
Error
minations
-0.01 + 0.01 0.00 +0.02
r0.02 i 0.01
+0.01 +0.03
zo.01
z0.02 io.01 k0.02
Table V. Analysis of Rock Phosphate and Steels
Figure 3. Molar ratio method
below (Determination of Vanadium in Ilmenite). Stoichiometry of the Complex. T h e modified Job’s method of continuous variation (18), and the molar ratio method (19) were applied in the usual way to study t h e stoichiometry of t h e complex. Job’s curves were constructed at different acidities (2-6 M HCl) and a t different wavelengths. In all cases, only one complex species, with the metal to ligand ratio 1:2 was indicated. T h e Job’s curves from extractions from 4 M HC1 are shown in Figure 2. Studies on molar ratio method did not yield plots with sharp breaks a t 2 mol of ligand per mol of vanadium (Figure 3) but results obtained on extrapolation point towards a 2:1 ligand-vanadium(V1 complex. E f f e c t of Diverse Ions. Forty-five pg of vanadium per 25 ml of aqueous solutions was determined in t h e presence of various amounts of fifty-two diverse ions. T h e tolerance limits (Table 111) show that vanadium can be determined in the presence of 1:2500 to 1:lOOO of a great number of diverse ions including most of those which are commonly associated with vanadium in natural and synthetic mixtures. Tolerance limits for Ti4+ increased substantially in the presence of fluoride, and Mo(VI), W(VI), and Zr(1V) were tolerated to a higher extent if phosphate was present. T h e maximum standard deviation in t h e multiple extractive determinations of different amounts of vanadium(V) in the presence of all the above-mentioned ions was ~k0.02(Table IV). D e t e r m i n a t i o n of V a n a d i u m in Ilmenite. A finely powdered sample of ilmenite (0.5 g) was fused with sodium hydrogen sulfate (10 g) till the sample completely decomposed. T h e melt was cooled and dissolved in 2-3 M sulfuric acid (40 ml) with heating. It was then filtered into a 250-ml volumetric flask, and made u p to the mark. T o a 20-ml aliquot of this solution, 3 ml of 10 M sulfuric acid was added followed by a 0.1% KMn04 solution (2 ml) and heating to
Std dev, Vanadium(V) found, pg
Vanadium Sample
Reported value
Mussoorie rock450 ppm phosphate (India) 0.1 7-0.19% Manganese steel (NBS, No. 6 7 ) 0.05-0.08% Ferrotitanium (NBS, No. 1 1 7 ) Chromium-vanadium 0.240% steel (BCS No. 224) High speed (BCS No. 1.570% 241/1 a Average of six determinations.
Founda
495 ppm 0.185% 0.076% 0.242% 1.569%
boiling for 10 min to oxidize vanadium(1V) to vanadium(V). T h e excess of KMn04 (pink color) was destroyed by dropwise addition of 1%sodium azide solution. Excess of azide was removed by heating. T h e solution was cooled and made faintly pink by dropwise addition of 0.1% KMn04 solution. I t was then extracted with 15 ml of 0.1 M DAMNHA solution for 2 min. After phase separation, 20 ml of 10-11 M hydrochloric acid was added and extracted again for 2 min. T h e organic phase was transferred to a second funnel, retaining the aqueous phase. T o the organic phase, 25 ml of a solution containing 20 ml of sodium triphosphate and 5 ml of 10 M sulfuric acid was added and extracted for 2 min. After settlement, the organic phase was transferred to a third separatory funnel, retaining the aqueous phase, and was extracted with 20 ml of 5 N hydrochloric acid for 1 min. T h e retained aqueous phases were washed with 5 X 2 ml of reagent solution and the washings, together with the main extract, were combined, dried, and measured as described before. D e t e r m i n a t i o n of V a n a d i u m in R o c k Phosphates. Samples ( 5 g) from Mussoorie Phosphate Deposits (India) were brought into solution (250 ml) by the method of Shapiro and Brannock (20). Aliquots (5 ml) of the “B” solu-
tions prepared as above were made -4 M in HCl and analyzed as described in the experimental section. T h e results are shown in Table V. Determination of Vanadium in Steels. Results of the analysis of vanadium in steel samples from the Bureau of Analyzed Samples Ltd. and the U S . National Bureau of Standards (Table V) point towards the precision and reliability of the present method.
ACKNOWLEDGMENT T h e author thanks S. C. Bhattacharyya and G. K. Trivedi for invaluable suggestions, the authorities of Saifia College, Bhopal, and B. G. Bhat and R. S. Singh of t h e Department of Chemistry, I.I.T. Bombay, for providing facilities. Skilled technical help from Jameel Ahmed is acknowledged.
(4) (5) (6) (7) (8) (9) (10)
(11) (12) (13) (14) (15) (16) (17) (18) (19) (20)
S.G. Tandon and S. C. Bhattacharyya, Anal. Chem., 33,
1267 (1961). U. Priyadarshini and S. G. Tandon, Analyst(London),86, 544 (1961). D. C. Bhura and S. G. Tandon. Anal. Chim. Acta, 53, 378 (1971). Y. K . Agrawal. Anal. Chem., 47, 940 (1975). U. Tandon and S. G. Tandon, J. lndian Chem. SOC., 46, 983 (1969). D. C. Bhura and S. G. Tandon, lndian J. Chem., 8, 1036 (1970). S. G. Tandon and S. C. Bhattacharyya, J. lndian Chem. SOC.,47, 583 (1970). A. K . Majumdar, "N-Benzoylphenylhydroxylamine and Its Analogues", Pergamon Press, New York, 1972. V. K . Gupta and S. G. Tandon. Anal. Chim. Acta, 66, 39 (1973). Y. K. Agrawal. M. C. Chattopadhyaya, S. A . Abbasi, and M. G. Bodas. Separ. Sci., 7, 613 (1973). R. M. Cassidy and D. E. Ryan, Can. J. Chem., 46, 327 (1968). S. A. Abbasi, J. Chem. Assoc., in press. W. F. Hillebrand. G. E. F. Lundel, H. A. Bright, and J. I. Hoffman, "Applied Inorganic Analysis", 2nd ed., Wiley. New York. 1953. E. B. Sandell. "Colorimetric Determination of Traces of Metals", 3rd ed., Interscience, New York, 1959. W. C. Vosburgh and G. R. Cooper, J. Am. Chem. Soc., 63, 437 (1941). A. E. Harvey and D. L. Manning, J. Am. Chem. SOC., 72, 4488 (1950). L. Shapiro and W . W. Brannock, "Rapid Analysis of Silicate, Carbonate, and Phosphate Rocks", U.S. Geol. Surv. Bull., 1144-A:45 1962.
LITERATURE CITED (1) U. Priyadarshini and S. G. Tandon. Anal. Chem., 33, 435 (1961). (2) H. Tomioka, Bunseki Kagaku, 12, 271 (1963); Chem Abstr., 59, 5768 (1963). (3) E. S.Pilkington and W. Wilson, Anal. Chim. Acta, 47, 461 (1969).
RECEIVEDfor review October 28, 1975. Accepted December 8, 1975. T h e author is graLefu1 to the C.S.I.R., New Delhi, for a Senior Research Fellowship.
Computer Searching of Infrared Spectra Using Peak Location and Intensity Data R. C. Fox Chevron Research Company, Richmond, Calif. 94802
A computer program has been written that uses the filesearching technique for matching reference spectra with unknown infrared spectra. Both peak location and peak intensity data are used. A library of reference compounds has been generated which contains over 6000 spectra. The basic logic involves checking each peak of the reference compound with the peak of the unknown spectra using various criteria. The matches or mismatches are then scored or handicapped using factors determined by experiments to give useful results. A list of the top scoring compounds is presented in the output. The program is mainly aimed at identifying unknown materials, particularly those that occur in commercial products.
Several computer systems for searching spectral files are reported in the literature. These include: mass spectra (14 ) , proton magnetic resonance spectra (51, general approaches to all spectra (6-8). Several papers have been published on searching infrared spectra. These include pattern recognition techniques (9, 10) as well as file-searching methods ( 11-1 7 ) . Generally available file-searching approaches for searching infrared spectra (18, 19) are mainly based on the large data base provided by the American Society for Testing and Materials (ASTM). However, the ASTM data does not include intensity information. This paper reports on an approach that uses both peak location and intensity data. Because the infrared spectra for compounds are often quite unique, the spectra contain a large amount of information. Such a characteristic strongly suggests that if the proper representations or models of the spectra can be chosen, both a minimum of calculating effort should be re-
quired for a computer, and the spectra should not have to be characterized by highly precise measurements. The basic approach taken in this paper is to build on the approaches already reported (12-14, 17, 1 8 ) in developing both the data files and the fundamental logic. From this fundamental logic, there then evolved several different strategies aimed at different types of search. A central feature of this evolution was the experimental use of the computer. T h e spectra of known materials or mixtures were submitted to many computer runs in the study of a particular strategy in order to test its usefulness.
EXPERIMENTAL Equipment. Most of the infrared spectra. other than published data, were obtained on a Perkin-Elmer 467 grating spectrophotometer. Some of the earlier data for the library were obtained with a prism spectrophotometer. T h e computer runs were made on an IBM 370/168 VS2 system. Run time for a pass through the reference spectra normally takes hetween 8 and 10 CPU seconds. Program. T h e computer program is written in FORTRAN IV language. I t also provides for entering new d a t a into the reference library, punching cards, etc. T h e size of the program is about 140K. Reference Spectra. Input data for new reference spectra also contain t h e names of the compounds and code numbers for t h e location of spectra. T h e infrared d a t a itself can be either in t h e form of wavenumbers or wavelengths ( t o the nearest tenth of a micron). Intensities are entered as the number l for a strong intensity peak (arbitrarily set a t a transmittance less t h a n 20961, 2 for a medium intensity peak (transmittance between 20 and SO%), and 3 for a weak peak (for greater than 50% of transmittance). T h e program includes a data-checking step t o catch obvious coding errors. Data for Unknown Input. Data input for a program run includes the name of the unknown plus the capability for handling up to 120 peak locations and intensities. Data can be entered either in the wavenumber form or the wavelength form. T h e peak intensity can be assigned the number 1, 2, or 3, as described for t h e reference compounds. In addition, one can use an intensity numANALYTICAL CHEMISTRY, VOL. 48, NO. 4 , APRIL 1976
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