Accuracy. Chloride-free corn meal samples are fortified with various organochlorine compounds a t t h e 0.4-p.p.ni. chloride level. The compounds are rhlorotetracycline, chloranilihenicol, p,p’-DDT, griseofulvin, caldariomycin, and. Drosophilin A ; except for D D T , these are all naturally occurring chlorine-containing compounds. The compounds are added t o the corn meal both in solution and in the dry form. After b l h g blended, each sample is air dried, then extracted with n-hexane in the ueual manner. The hexane extracts are aliquoted, concentrated, and analyzed in quadruplicate by the present technique as well as by neutron activation ( 3 ) . Results are shown in Table IV. Range Affects. T h e slope of a calibration curve i:j dependent upon t h e range used for t h e recorder. I n Figure 9, DDT standard curves are plotted for 4 range:, from 5 to 50 mv. t o illustrate this paint. Other Factors. As discussed by Helmkamp et al. (6) and as mentioned earlier, certain inorganic ions interfere in this method. .ilso, precision temperature control a t the sensor electrode is essential by virtue of the Sernst equation.
Table IV. Comparative Analytical Results of Standard CI- Fortified (0.4 p.p.m.) Corn M e a l Samples b y the Present Method vs. Neutron-Activation Analysis
C1- found, p.p.m. Seutron-activation Chlorinated compound added Present method analysis” None 0.0,o. l , o .0 0.08 f 0.02 Chlorotetracycline 0.5 f 0.1 0.36 f 0.08 0.5 f 0.2 0.50 f 0.10 Chloramphenicol 0.5 f 0.1 0.49 f 0.03 P,P‘-DDT Griseofulvin 0 . 5 It 0 . 1 0.53 f 0.10 0.41 f 0.08 Caldariomy cin 0.4 f0.1 Drosophilin A 1.3 f 0.3 1.83 f 0.03 Solvent alone 0.02 f 0 . 0 1 0.015 f 0.003 a After 1OX concentration of the extractive solution. ACKNOWLEDGMENT
The authors are grateful to John E. Leonard, of Beckman Instruments, Fullerton, Calif., for invaluable assistance and suggestions during the entire course of this work. LITERATURE CITED
(1) Agazzi, E. J., Peters, E. D., Brooks,
F. R., ANAL.CHEM.25, 237 (1953). ( 2 ) Aronson, 11. H., Kezer, C. F., “100 Electronic Circuits,” Vol. 1, p . 155,
Pittsburgh Instruments Publishing Co., Pittsburgh, Pa., 1957. (3) Guinn, I-.P., Schmitt, R. A,, Residue Rev. 5 , 148 (1964). (4) Gunther, F. A., Blinn, R. C., “Analysis of Insectirides and Acaricides,”
PP. 357-70, Interscience-Wiley, Sew Yorl Proc. I.R.E. 4 3 , 701 I
_
^
_
(19.55). \ _ _ _ .
(11) White, T. T., Penther, C. J., Tait,
P. C., Brooks, F. R., ANAL. CHEM. 25, 1664 (1953). RECEIVEDfor review April 19, 196s. Accepted J ~ l y22, 1965. Supported in part by U.S.P.H.S. grant No. EF-00029.
Spectrophotometric Determination of Antimony R. M. MATULIS and J.
C. GUYON
Department of Chemistry, Universify of Missouri, Columbia, M o .
b A sensitive, spectrophotometric technique for antimony has been developed. The method i s based upon the enhancement b y antimiony o f a blue hue due to the reductiori of the molybdate aGgregate near p t i 1.4. The addition of a large excess of Na2S04 minimized the blank and aided the reproducibility of the system. Spectral data indicate an interaction of Sb(lll) with the molybdate aggregate under conditions of the analysis. The method i s sensitive for antim’ony in the range of 0.02 to 1.6 p.p.m. The molar absorptivity can b e calculated to b e 1.1 X The method i s subject to several interferences but the antimony can be cleanly separated as the volatile chloride in a Scherrer apparatus. Good results were obtained on NBS 5 4 d Sn-base bearing metal.
lo5.
A
NEW, SENSITIVE spectrophotometric technique for determining micro amounts of antimony has been developed. Many of the current methods in use employ organic chromogenic
reagents which form antimony complexes extractable into nonpolar phases on which absorbance measurements are made. The most common of these techniques have employed Rhodamine B ( 7 , 13, 17, 26, 28), methyl violet (16, 23), Brilliant Green (6, 11, 24), phenylfluorone, (8, 19, 21), and crystal violet (12, 25). These methods are satisfactorily sensitive, but suffer from a number of interferences, and require extraction steps. The method proposed here has even greater sensitivity than the above techniques and has no extraction step. The interferences are readily separable. Other current methods rely upon complex formation in the aqueous phase to develop color proportional to the antimony concentration. Iodide ion in acid solution (4, 5 , 14, 18, 20, 27), or with iodide and pyridine (2) have been used, but not with the sensitivity of the above methods. The yellow complex formed with thiourea has been applied with some success (1). KO heteropoly acid technique has been developed in which antimony be-
comes the central element coordinated with molybdate or other hetero-atoms. Advantage has been taken of the sensitivity of heteropoly acids to weak reducing agents in acidic solutions. Sb (111) has been used to reduce molybdophosphoric acid (9), molybdovanadosilicic acid (10) and molybdotungstophosphoric acid (15) to the soluble “heteropoly blue,” the intensity of the blue hue being proportional to the Sb (111) content. This paper reports the results of a study designed to develop a spectrophotometric method for antimony and to continue an investigation into heteropoly acid formation. EXPERIMENTAL
Absorbance measurements were made either on a Cary Model 12 recording spectrophotometer, or on a Beckman D U spectrophotometer each with matched 1-em. quartz cells against double distilled water . Emission spectra were taken on a Jarrell-Ash 480-cm. emission spectrograph with a Wadsworth mounting. Apparatus.
VOL. 37, NO. 11, OCTOBER 1965
1391
Polarographic measurements were made on a Sargent Model XV recording Polarograph. Measurements of p H were made on a Beckman Expanded Scale line-operated meter. Appropriate Fisher standard buffers were used. Glassware was calibrated according to standard procedure. Reagents. A reagent mixture consisting of Na2M004.2H20, H2S04, and Na2S04 was prepared by mixing 240 ml. of 5y0 (w./v.) sodium molybdate dihydrate, 800 ml. of 1M sodium sulfate, and 80 ml. of 1 : 3 H2S04, and diluting with distilled water to the mark in a 2-liter volumetric flask. Mallinckrodt reagent grade chemicals were used. This solution was stored in a polyethylene bottle and allowed to stand a t least 24 hours. Ascorbic acid, 5% (w./v.), . was prepared fresh daily by dissolving 5.000 grams of Fisher reagent grade ascorbic acid and diluting to the mark in a 100ml. volumetric flask with double distilled water. The opened reagent bottle was stored over magnesium perchlorate to avoid decomposition. Standard Sb(II1) solutions were made in two ways. ( a ) . Weigh 200.0 mg. of Fisher reagent powdered antimony metal, add 125 ml. of concentrated H2SO4, heat over a free flame to accomplish solution, and dilute to 1 liter in a volumetric flask with double distilled water. Oxidation proceeds to the (111) state only. The purity of the antimony metal was established bv sDectrographic analysis. ( b ) . Weigh 10.000 grams of clear desiccated crvstals of SbCla and dilute to the mark- in a 250-ml.. volumetric flask with anhydrous methanol. Fisher reagent grade was used. The antimony content was established by titrating aliquots of the stock solution with KBrOa in 3N HC1 using Naphthol Blue Black indicator. The C1- was titrated potentiometrically using standardized AgSOa. Direct and indirect analysis agreed on Sb content. Five milliliters of the methanolic SbC13 stock solution was diluted to 100 ml. in a volumetric flask with anhydrous methanol, The final standard solution contained 2.0 mg. of SbCL per ml. Recommended Method. Based partly on previous knowledge and partly on empirical experimentation, the following recommended procedure was evolved. PREPARATION OF CALIBRATION CURVE. Prepare a calibration curve by adding 0.00, 0.20, 0.40, 0.60, and 0.80 ml. of the standard Sb(II1) in HISOl solution to 100-ml. volumetric flasks. To each flask add 20 to 40 ml. of HzO, washing the sides. To each flask, in the following order, add 1 drop of phenolphthalein, and 0.5X NaOH to the first permanent pink. Add 1.00 ml. of 5% ascorbic acid. Start the timer, and simultaneously add 50.0 ml. of the molybdate reagent mixture. Dilute t o the mark, mix, and place in a constant temperature bath a t 25' i '1 C. This sequence of steps requires approximately 2 minutes, so a series of flasks is prepared. Read each sample 1392
ANALYTICAL CHEMISTRY
la 1.7 14
1s
-
*
-
. . 1.2 . 1.4
1.s
0
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3:O l m l o f I : 3 H 2 S 0 , ~
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Figure 1.
after a measured development time of 30.0 minutes at 725 mp us. double distilled water. Plot absorbance vs. p.p.m. of Sb. GENERAL PROCEDURE. The antimony must be in the I11 oxidation state. If the Sb is in the V state, it may be reduced with SO2 or hydrazine. If the sample is an alloy, the Sb can be placed in the (111) state by dissolution in concentrated H2S04over a free flame, followed by dilution after cooling. Antimony may be separated from interferences in the following manner. The dissolved sample is placed in a Scherrer apparatus (?B), followed by 5 ml. of concentrated HaP04. Carbon dioxide is passed in and the solution is heated to 150' C. while adding 75 ml. of concentrated HCl dropwise over a 1 to 2 hour period. The distillate is collected and diluted to a specified volume from which aliquots that lie in the range of the calibration curve may be taken. Proceed with the analysis as under preparation of the calibration curve. Analysis for phosphate showed none to be distilled over under these conditions. RESULTS AND DISCUSSION
To obtain a system for the spectrophotometric determination of antimony, consideration must be given to the process of complex formation, and to the reduction of the molybdate to the molydenum blue. Several factors influence each of these processes. Preliminary Studies. Preliminary studies consisted of systematically varying the concentrations of H2S04, Na2Mo04,and ascorbic acid until the addition of Sb(II1) produced a marked enhancement of the reduced molybdate. The absorption spectrum was taken and showed a broad absorption from 720 to 750 mp. Reduced molybdate usually absorbs a t 725 mp. This wavelength was used in all subsequent measurements.
Effect of pH
Effect of pH. The p H had to be studied in order to obtain the maximum enhancement. Molybdate systems operate under differing p H conditions and p H studies are necessary in every case. Figure 1 shows the typical p H dependence of the system. This study was made by mixing 0.20 ml. of 2000 p.p.m. methanolic SbCla, 1.0 ml. of 5% ascorbic acid, and 50 ml. of a reagent mixture containing 6 ml. of 5% sodium molybdate, 20 ml. of 1M sodium sulfate, and varying amounts of 1:3 H2S04 to 100ml. volumetric flasks. The flasks were diluted to the mark with double distilled water and read a t 725 mp after a measured development time of 30.0 minutes. A pH of 1.38 (2.0 ml. of 1:3 H~S04/100ml.) was chosen for use here because it gave a maximum color enhancement and the pH dependence w&s small. When a study of variables was begun, methanolic SbCla was used as a source of antimony. This was necessary because it wm known that the system would be p H sensitive and an aqueous source of antimony would necessarily be very acid. For close pH control, methanolic SbCla was used. It was later discovered that the p H problem could be circumvented by adding aqueous acidic antimony, and neutralizing the excess acid with NaOH followed by the usual order of addition reagents. An increase in sensitivity for antimony by this technique was observed, and it was incorporated into the procedure. Effect of Molybdate Concentration. The effect of molybdate concentration was studied by adding 0.20 ml. of 2000 p.p.m. methanolic SbCla, 1.0 ml. of 5Y0 ascorbic acid, and 50 ml. of a reagent mixture containing varying amounts of 5% sodium molybdate,
1.8
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.9-
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Figure 2. tration
Effect of molybdate concen-
2.0 ml. of 1: 3 H2SOd,and 20 ml. of 1 X sodium sulfate to LOO-ml. volumetric flasks. The flasks were diluted to the mark with double distilled water and read a t 725 mp after a measured development time of 30.0 minutes. The results of this study are shown in Figure 2. Six milliliters of 5% sodium molybdate was chosen because the system was reproducible and gave an intense absorbance. Using the peak value requires working at 2 higher total acid concentration and gives rise to instability in the system. Effect of Sulfate Concentration, Empirically, t h e addition of sodium sulfate in a large excess led to a more stable, reproducible cjystem. T h e system was further aided by giving only a minimum blank under these conditions. The effect of t h e sulfate concentration was studied by mixing 0.20 ml. of 2000 13.p.m. methanolic SbC13, 1.0 ml. of 5% ascorbic acid, and 50 ml. of a reagent mixture containing 6 nil. of 5% sodium molybdate, varying amounts of 1-11 sodium sulfate, and 2.0 ml. of 1: 3 H2S04to 100-ml. volumetric flasks. The flasks nere diluted to the mark with distilled water and read at 725 mp after a measured development time of 30.0 minutes. Results of this study are shoan in Figure 3. Twenty milliliters of 121 Na2S04 was chosen because it eserted a controlling effect a t this concentration and the sulfate concentration dependence is small a t this level. Sulfate concentration dependence here has only ii relative meaning since H2SO4 was used for pH adjustments. Effect of Time. ’The time of color delelopment was studied by adding 0.20 ml. of 2000 p.p.m. methanolic SbC13, 1.0 nil. of 5% ascorbic acid, and 50 rnl. of t h e reagent mixture described under Reagents to a 100-ml.
volumetric flask. The flask was diluted to the mark with double distilled water and read at 725 mp after mixing. The absorbances were read at intervals of time keeping the temperature constant to within =t1’ C. Results of this study are shown in Figure 4. Thirty minutes was chosen as the optimum time. Greater intensity developed than a t shorter times and longer development times led to irreproducibility. Because the absorbance was changing with time, it \\as necessary to make the final reading at 30.0 minutes. Deviations from this time by +O.l minute produced errors of a t most 0.01 p.p.m. Aging of Reagent Mixture. Several steps could be eliminated and greater accuracy could be obtained by miying the molybdate, sulfate, and sulfuric acid solutions to the proper ratio so t h a t the reagents could be added as one unit t o the 100-nil. volumetric flasks. However, the freshly mixed components gave lower absorbances than a solution several days old. A freshly prepared reagent mixture (see under Reagents) was delivered into a 100-ml. volumetric flask containing 0.20 ml. of 2000 p.p.m. methanolic SbCl3, 1.0 ml. of 570 ascorbic acid, and 30 ml. of HzO. The absorbance vias read a t 7 2 5 mp after 30.0 minutes development time. This experiment was repeated at various times after the initial preparation of the reagent mixture. Figure 5 shows the results of this study and a n identical study using an equivalent amount of ammonium heptamolybdate. Dehne and llellon ( 3 ) discuss a niolybdatesulfate complex that is formed in systems similar to these. The effect may also be due t o the time necessary for the molybdate aggregate to form. Only six hours are required for equilibrium to be attained in the heptamolybdate study. As a result of this study, at least 24 hours was permitted to elapse before the reagent mixture was used.
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Figure 3.
Effect of sulfate concentration
Choice of Reductant. Numerous reductants commonly employed in t h e reduction of molybdates were studied. Chlorostannous acid, ferrous ion, hydrazine sulfate, sulfonic acid-sulfite, hydroquinone, formaldehyde, “Elon,” and dextrose were studied along with ascorbic acid. Ascorbic acid was chosen because it gave greater enhancements in shorter development times than the other reductants. Chlorostannous acid, hydroquinone, formaldehyde, and dextrose gave no enhancement. Effect of Concentration of Reductant. The effect of concentration of ascorbic acid was studied by adding varying amounts of 5% ascorbic acid to 100-ml. volumetric flasks along with 0.20 ml. of 2000 p.p.m.
-
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VOL. 37, NO. 1 1, OCTOBER 1965
1393
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Figure 5.
PO 94 28 TIME, HOURS
8.
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Effect of Diverse Ions
Added as
Amount permitted, p.p.m. 20 20 5
~ 1 + 3 +
5 30 30 20
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40
44
48
Heptamolybdate Molybdate
methanolic SbC13, and 50 ml. of the reagent mixture. The flasks were diluted to the mark and absorbances were measured at 725 mh after 30.0 minute development. Absorbance increased rapidly with increasing amounts of ascorbic acid. One milliliter of 5% ascorbic acid was chosen for subsequent use. Greater reproducibility was obtained with smaller volumes of ascorbic acid, but it was necessary to use enough to give a marked enhancement. Effect of Volume before Adding Reagent Mixture. This was studied by adding 1.0 ml. of 5y0 ascorbic acid and 0.20 ml. of 2000 pap.m.methanolic Table 1.
32
Spectra of Sb-molybdate species 1. 2. 3. 4.
Blank 4 m g . of SbCls 8 mg. of SbC13 16 mg. of SbC13
Aging of reagent mixtures A.
NH4 As
430 440 450 460 470 480 490 500
x (4
fi 4
0
420
ANALYTICAL CHEMISTRY
SbC13 t o 100-ml. volumetric flasks. Varying amounts of water (up to 50 ml.) were added and 50 ml. of the reagent mixture was added. The flasks were diluted to the mark and the absorbances measured a t 725 mp after 30.0-minute development times. The effect was negligible above 10 ml. No efforts were made to control the volume above this value. Effect of Light, Amount of Methanol, and Dissolved 02, Nz. S o significant deviations occurred when the effect of light and the effect of the amounts of methanol and dissolved O2 and N2 were studied. Effect of Temperature. The reduction step was subject t o large temperature changes. Higher temperatures gave greater absorbance values for solutions with and without antimony, b u t the actual enhancement due to antimony was not significantly greater a t higher temperatures. The convenience of working at room temperature and the fact that the sensitivity of the system was not increased by higher temperatures led to a choice of 25' f1' C. for all measurements. Effect of Diverse Ions. To study the effect of diverse ions, 0 to 100 p,p.m. of the ion was added to 100ml. volumetric flasks along with 0.20 ml. of 2000 p.p.m. methanolic Sb(%, 1.0 ml. of 57G ascorbic acid, and 50 ml. of t h e reagent mixture. The solutions were diluted to the mark and read a t 725 mp after 30.0-minute development times. The results of this study are summarized in Table I. A 2% relative error was considered tolerable. I n addition to the ions in the table Ag+, Pb+2, Ba+Z, and Sr+2 form insoluble precipitates and Bif3, c103-, Io4-, Crz01-2, S i 0 c 2 , Ta+5, and HP04-* interfere seriously. No deviation in effect of diverse ions
was observed when aqueous antimony was used. Conformity to Beer's Law. After the optimization of the variables described above, varying amounts of standard S b l I I I ) a e r e added t o otherwise identical solutions and t h e reductions were carried out. The system followed Beer's law in the range 0.02 to 1.6 p.p.m. Standard Sb(II1) in HzS04 was used in preference to the methanolic SbC13 because of the general inconvenience of pipetting methanolic reagents. The molar absorptivity can be calculated to be 1.1 X lo5. Accuracy of Method. The method was evaluated by digesting 0.5062 grain of KBS 54d Sn-base bearing metal in 20 ml. of hot concentrated H2S04. The Sb was separated by distillation as described under General Procedure. The distillate was diluted to the mark in a 250-ml. volumetric flask. Paper chromatographic analysis of the distillate using Whatman KO. 3 MM and butanol/aq. HC1 revealed only Sb a h e n developed with HzS. Four 0.5-ml. aliquots of the distillate were removed for analysis. The average of four determinations showed the aliquot to be 0.72 p.p.m. in Sb. The NBS certified value showed the aliquot to be 0.71 p.p.m. in Sb. The relative error was 1.470. CHEMICAL SYSTEM
Studies are being conducted in an effort to explain the chemistry in the system. Ultraviolet spectra of Sb(II1) and ascorbic acid in acidic solution indicate no interaction. The polarographic halfwaye of Sb(II1) is not shifted in the presence of varying amounts of ascorbic acid in HC1 medium, or the medium in which the analysis is carried out. Visible spectra were taken from 500 to 330 m p of solutions identical to the analytical conditions with varying
amounts of Sb(II1). Fifty milliliters of the reagent mixture were added to 100 ml. volumetric f l a s h which contained 0, 2.0, 4.0, and 8.0 ml. of 2000 p.p.m. methanolic SbC13 and were diluted to the mark. Spectra w e shown in Figure 6. The bathochromic shift can be attributed to a n antimony interaction with the molybdate aggregate. A yellow compound can be prepared by mixing SbC13 in HC1 with aqueous sodium molybdate. Spectrographic analysis indicates ih a t this material contains only antimony and molybdenum in major amounts. Efforts are being made to characterize this substance more completely. Apparently the role of ascorbic acid is not unique, because enhancement can be obtained with other reducing agents, but the mechanism of oxidation of ascorbic acid may lead to products nhich do have unique properties. LITERATUI!E CITED
(1) Akhmedli, 11. K., Granovskaya, P. B.,
C'ch. Zap. AzeTb. Cbs. C'niv., Ser., Fzz. Alfat. i K h ~ m .Yauk. . (2) 49-52 (1962); Anal. Abstr., January 1964, Abstr.
KO. 106.
(2) Clarke, S. G., Analyst 53, 373 (1928). (18) Maeur, H., Roczn. Zahl. Hig., (3) Dehne, G. C., Nellon, M. G., A N ~ L . Warsaw 11, (31, 217-25 (1960); Anal. CHEM.35,1382 (1963). Abstr., May 1961, Abstr. No. 2140. (4) Dym, A., Analyst 88,232 (1963). (19) Mustofin, I. S., Ivanova, A. N., ( 5 ) Elkind, A., Gayer, K. H., Boltz, Izv. Vgosk. Ucheb. Zavedeniu, Khim. i D. F., ANAL.CHEM.25, 1744 (1953). Khim. Tekhnol. 5, (3), 504-5 (1962); (6) Galliford, D. J., Yardley, J. T., Anal. Abstr., November 1963, Abstr. Analyst 88, 653 (1963). No. 4680. (7) Greenhalgh, R., Riley, J. P., Anal. (20) Ploum, H., Arch. Ezsenhuttenw 33 Chim. Acta. 27, (3) 305 (1962). (a), 601-4 (1962); Anal. Abstr., June (8) Gurkina, T. V., Konovalova, K. M., 1963, Abstr. No. 2291. Tr. Kazakh. Nauch.-Issled. Inst-Mineral (21) Rozenblyum, E. N., Pocktman, Sgr'ya ( 5 ) , 249-54 (1961); Anal. Z. Y., Zavad. Lab. 29,929 (1963). Abstr., April 1963, Abstr. No. 1394. (22) Schemer, J. A., J . Res. iVat1. Bur. (9) Kokorin, A. I., Zavad. Lab. 12, 64 Std. 21,95 (1938). (1946). (23) Silaeva, E. V., Kurbatova, V. I., (10) Kokorin, A. I., Polotobnova, N. A., Zavod. Lab 28, 280 (1962). Trudy Konnassa Anal. Kim. 7, 205 (24) Stanton, R. E. McDonald, A. J., (1958). Analyst 87, 299 (1962). (11) Kristaleva, L. B., Tr. Tomsk Univ. (25) Studlar, K., Janousek, I., Collection 154, 271-4 (1962); Anal. Abstr., May Czech. Chem. Commun., 25, 1965-9 1964, Abstr. No. 1691. (1960); Anal. Abstr., hlarch 1961, (12) Leu, Y. C., Acta. Pharm. Sinica 7, Abstr. No. 996. (26) Tanaka, AI., Kawahara, >I., Japan ( 5 ) , 171 (1959,. Analyst 10, (2) 185 (1961). (13) Luke, C. L., ANAL. CHEM.25, 674 (27) S'olodarskava. R. S.. Zavod. Lab. (1953). ' 25, 143 (1959): ' (14) LIcChesney, E. V., IND. ENG. (28) Ward, F. N., Lakin, H. W., ANAL. CHEM.ANAL.ED. 18, 146 (1946). CHEM.26, 1168 (1954). (15) Makishima, S., J . SOC.Chem. Ind. Japan 34, Suppl. binding, 322 (1931). RECEIVEDfor review March 1, 1965. (16) llaksai, L. I., Silaeva, A. A,, Sb. Accepted July 27, 1965. Work supported Tr. Vses. Sauchn-Issled Gorn.-Metallurg. by the Director of Chemical Sciences, Inst. Tsvet. Met. (7)) 343 (1962); Anal. Air Force Office of Scientific Research, Abstr., January 1964, Abstr. S o . 57. under Grant AF-AFOSR-205-63. Ana(17) llaren, T. H., ANAL.CHEM.19, 487 chem Conference, Detroit, Mich., October 15, 1964. (1947).
Specific IDetection and Determination of Cyanide Using Various Quinone Derivatives GEORGE G. GUILBAULT and DAVID N. KRAMER Defensive Research Division, Chemical Research and Development Laboratories, Edgewood Arsenal, Md.
b p-Benzoquinone, N-chloro-p-benzoquinoneimine, and 0-(p-nitrobenzene sulfonyl) quinone monoxime are suitable reagents for a simple, direct method for the specific detection of small quantities of cyanide. Addition of as little as 0.2 pg. of cyanide per ml. of total solution to these reagents yields a highly fluorescent product. The fluorescence produced in the reaction of p-benzoquinone with cyanide i s proportional to the cyanide concentration over the range 0.2 to 50 pg. No other ions interfered in concentrations up to 0.l'M. The order of the rate of reaction and sensitivity increased in the general order 0-(pnitrobenzene sulfonyl) quinone monN-chloro-p-benzoquinoneoxime imine < p-benzoquinone. The order of fluorescence intensity increased in the order of solvents used: dioxane ethyl formate
