Analytical Procedure. Samples containing 500 mg. of capsules were either crushed in a tissue grinder or in a Wig-L-Bug (Crescent Dental Mfg. Co.), then extracted with 5 to 10 ml. portions of benzene. Both methods of extraction were found suitable for recovering the encapsulated CIPC from the capsules. The benzene solution was quantitatively transferred through filter paper into 25 ml. volumetric flasks. A set of standards containing 0, 5, 10, 15, and 20 mg. per ml. of CIPC in benzene were also prepared. Sample and standard solutions of 40 pl. were injected into the gas chromatograph. The column temperature and detector were maintained at 190' C. with the injection port at 210' C. Helium flow rate was 60 cc. per minute, detector current was held at 250 ma., and an attenuation of 8 x was required for the detector signal. Retention time for the CIPC was 4'/* minutes. Areas of the component peaks were calculated by triangulation, and the areas for the standards were plotted against concentration of CIPC. Concentration of the herbicide in the samples was obtained by comparing the CIPC peak areas of the samples with the standard curve. RESULTS A N D DISCUSSION
Table I gives the results of the areas obtained for the various concentrations of CIPC in the standard solutions. A plot of this data is a straight line which passes through the origin. The relative standard deviation for a series of five replicate injections of an extracted sample containing 76% CIPC was
*1.8%. Figure 1 shows a chromatogram of the separation attained for a typical sample. Since this method was developed for high concentrations of CIPC, the determination of trace amounts was not our main concern. However, trace analyses might be accomplished by utilizing the proposed chromatographic conditions and substituting flame ionization or electron capture detection for the thermal conductivity detector. This procedure affords a rapid means of assaying the herbicide in mixtures of inert carriers which could be useful for control purposes. The appearance of numerous pyrolytic products in the chromatograms obtained in the initial studies showed the limitations of attempting a direct gas chromatographic separation of the carbamate, CIPC, a t high temperatures. However, under the proposed conditions, only one niajor symmetrical peak was observed. The component associated with this peak was collected in a cold trap by repeated injections of CIPC. Infrared examination of the condensate taken from the cold trap gave the same spectrum as the CIPC before gas chromatography. Caution was required in collecting the CIPC. If the CIPC condensed a t the exit port where the collecting capillary was attached and not in the cold trap, gradual decomposition took place. The infrared spectrum of the material which condensed a t the relatively hot exit port was similar to that of CIPC. A band at 4.5 mp,
Table 1.
Data for Standard Curve of CIPC Vs. Peak Area
Concn. CIPC, Mg.
Area, sq. mm.
0.so
988 764 499 256 0
0.60 0.40 0.20 0
indicative of a nitrile group, was the major difference observed. Therefore, this decomposition was presumed to have taken place in the exit port vicinity, not on the column. The CIPC collected in the cold trap showed no detectable decomposition, and the areas of the CIPC peaks are linearly related to the concentration as shown in Table I. Thus it is concluded that the residence time of the CIPC in the column (41/2 minutes a t 190" C.) has no adverse effect on the precision or accuracy of the method. LITERATURE CITED
(1) Gard, L. N., Rudd, N. G., J. dgr. Food Chem. 1, 630 (1953). (2) Gutenmann, W. H., Lisk, D. J., Ibid., 12,46.(1964). ( 3 ) Kowistonmen, P., KarinpaL, A., Ibicl., 13,459 (1965).
RONALD J. ROMAGNOLI JAMES P. BAILEY Wallace & Tiernan Inc. Harchem Division Belleville, N. J.
Rapid Extraction and Spectrophotometric Determination of Pa Ila diu m (11) with Isonitrosoacetyfacetone SIR: It is well known that isonitrosoacetylacetone (HINAA) reacts with iron(I1) ( I ) and cobalt(I1) (6) t o give colored complexes which are extractable into organic solvents. However, its use for the extraction and spectrophotometric determination of metals has not been reported. Palladium(I1) reacts with HINL44to give a yellow complex extractable into nonpolar solvents such as carbon tetrachloride, benzene, etc. This reaction has been utilized to develop a method for the rapid extraction and simultaneous spectrophotometric determination of palladium. EXPERIMENTAL
Apparatus. dbsorbance measurements were taken on a Hilger and Watts ultraviolet spectrophotometer using 1-cm. silica cells. A Unicam colorimeter, Model S P 300, was also employed in some experiments. A pH meter, Type PHM22r, made by
Radiometer, Copenhagen, Denmark, was used for p H measurements. Reagents. A.R. grade chemicals and reagents were used. All solutions were prepared in double - distilled water. The stock solution of palladium was prepared by dissolving palladium chloride in HCl and diluting the solution to a known volume. The palladium content of the stock solution was estimated by the dimethylglyoxime method (4). A 2% aqueous solution of HINAA, prepared according to the procedure described by Welcher ( 8 ) , was used. Solutions required for the interference studies were prepared by dissolving appropriate salts in water. The strength of each solution was determined by known methods ( 7 ) . Extraction Procedure. An aliquot of palladium solution (1 ml.) containing 1000 to 2000 pg. of Pd was placed in a 25-ml. beaker. Ten niilliliters of sodium acetate-acetic acid buffer solution of pH 6 and 1 ml. of the 2% aqueous solution of HINAA were added. For p H studies, the
buffer solution was omitted and the p H of the palladium solution was adjusted with dilute "03 or NaOH solution. The mixture was transferred into a 50ml. separatory funnel and shaken for 2 minutes with an equal volume of carbon tetrachloride or benzene. The two phases were separated and the palladium in each phase was estimated by the a-furildioxinie method ( 5 ) . The pH of the aqueous phase after extraction was measured. I n the study of the effects of other ions, the solution (1ml.) containing the ion was added before the adjustment of the pH of the solution. Calibration Curve. The solution was prepared as described above and then extracted thrice with 3 ml. of carbon tetrachloride. The combined carbon tetrachloride phase was transferred to a 10-ml. measuring flask and the volume was made up to the mark with the same solvent, The absorbance of the solution was measured a t 400 mp. Recommended Procedure. To a 1ml. solution containing 15 to 150 pg. VOL. 38, NO. 13, DECEMBER 1966
0
1929
E= Concn. of Pd in 1 ml. of CC14 Concn. of Pd in 1 ml. of aqueous phase
hcmp Figure 1.
Absorption spectrum of palcolor
ladium-isonitrosoacetylacetone in
CC14
A.
Pd = 2.343 X 10-4M, HINAA = 4.686 X 10-4M, pH = 6.0. Color extracted into 10
B.
ml. of CCla HINAA = 4 . 6 8 6 10-44 p~ = 4.58. Color extracted into 10 ml. of CC14
x
of P d in a 50-ml. separatory funnel,
0.1 nil. of 1M Hg(NOa)z solution is added and the pH is adjusted to 4-6. The resulting solution is treated with 10 nil. of sodium acetate-acetic acid buffer of pH 6 and 1 ml. of 261, solution of HINAA. It is then extracted and the absorbance measured as for the calibration curve. RESULTS AND DISCUSSION
The extraction of palladium with HINAA into carbon tetrachloride was investigated over the pH range 0.5 to 8. The value for the extraction coefficient ( E ) calculated from the relation
remains constant in the pH range 4 to 6. Below and above this pH range, it decreases. The results in Table I indicate that from a palladium chloride solution of pH 4 to 6, 96% of the palladium can be extracted by a single extraction with an equal volume of carbon tetrachloride. With palladium nitrate solution, a slightly higher value (97.4) for the percentage extraction of palladium is observed. The extraction of palladium into chloroform, benzene, or toluene is equally efficient but with the other solvents it is not so satisfactory. ,hot more than three extractions are necessary to achieve a quantitative extraction of palladium into CCl,. Palladium can be back-extracted into the aqueous phase by equilibrating a carbon tetrachloride solution twice with 5 ml. of 1N HCl. The yellow solution of palladiumHINAA complex in carbon tetrachloride shows an intense absorption peak (Figure 1) at 400 inw, so the absorbance of the solution is measured here, At this wavelength, the absorbance due to the reagent is negligible. The plot of absorbance-concentration of palladium gives a straight line in the range 1.5to 15 pg. of Pd per ml., indicating that Beer's law is obeyed. The molar absorptivity of the colored species at 400 mp is 9600 i 109 mol.-1 cm.-l, calculated on the basis of total palladium. The concentration of HINAA was varied from 0.16 to 15%, other factors being kept constant. One milliliter of 2% reagent solution is sufficient for extraction and color development in the range 15 to 160 pg. of Pd in 10 ml. of CC14. Excess of this reagent does not appear to have any effect on the intensity of the color. The absorbance of the CC14 solution measured at differ-
~
~~
Table I. Extraction Coefficients of Palladium(ll)-lsonitrosoacetylacetonate between Organic Solvents and Aqueous Solution as a Function of p H Total palladium taken = 1000 pg.
PH
Solvent
Extn. coeff.
Pd extrd. into organic solvent, yo
0.50 2.70 3.00 4.00 4.58 5.00 6.00 6.30 8.00 4,523 4.58 4.58 4.58 4.58 4.58
CCll
0.007 2.5 5.2 24.0 24.0 24.0 24.0 8.4 8.3 24.0 24.0 24.0 20.0 14.6 4.2
0.7 71.6 83.9 96.0 96.0 96.0 96.0 89.4 89.2 96.0 96.0 96.0 95.2 93.5 80.7
1930
e
ChloroformBenzene Toluene Ethyl acetate Iso-amyl alcohol Methyl ethyl ketone
ANALYTICAL CHEMISTRY
I
o'8
w
U 0.6
z m
a
2
0.4
m 4
t
0.2
0.0 0.2
0.4
0.6
0.R
1.0
R-
Figure 2.
Continuous variations plot
+
-
Vol. of Pd soln. vol. of HINAA s o h 2.0 ml.; 10 mi. of buffer of p H 4.6 added. Absorbance measured after extracting color thrice with 3 ml. of CCI4 0 0.001 8M solution of each reactant A 0.0027M solution of each reactant 0 0.0054M solution of each reactant
ent time intervals between 10 minutes and 72 hours did not show any significant change up t o 48 hours; after 72 hours it had decreased by 370. Several salting out agents such as Li, K, Mg, Ca, Ba, and Hg(I1) nitrates were tried to observe the effect on the extraction of the colored species into CC14. lLIercury(I1) nitrate increased the extraction in the chloride system, while other nitrates examined did not affect the extraction but interfered by reducing the color intensity in the CC14 phase. Mercury(I1) helps the extraction of palladium into CC11, probably because of its capacity to combine with chloride ions to form nondissociating HgC12. The competition of mercury for chloride ions promotes the formation of the extractable organic complex of palladium by preventing the formation of nonextractable chloro coniplexes of palladium. This e x p b nation also receives support from the observation that the extraction of palladium from nitrate solution is slightly better than that from chloride solution. The following ions, when present in amounts (mg.) noted in the parentheses, do not interfere colorimetrically: ~ t + 4 ( 2 0as ) PtCle-2, Pt+2(20) as PtC14-', ~ h + 3 ( 2 0 ) ,~ U + 3 ( 2 0 ) , os+y20), A U + ~ (lo), 1r~4(2) as IrC16-2, C0+~(20), Cu+2(20), Ni+2(20), FeT3(20), M n f z (120), ~ 1 + 3 ( 2 0 ) ,Ce"3 and Ce+,(20), Ut6(1O), Re+?(20),as Reo4-, Cd+2(20), Hg+2(20),Caf2(30), Sr +2(80), BaT2(50), Be+2(10), Pb+2(20), ?v1oL6(40), La+3 (SO), ~h+4(100),S04-2 (large excess), N03-(200), F-(20), C1-(35), Br-(50), Cr04-2(10), SeOe-2(270), P,0:-2(50), borate (501, tartrate (160), and citrate (50). The interference by the ions tabulated in Table I1 can be removed by adding appropriate masking agents. If chlo-
ride is not present, 60 mg. of silver can be tolerated. Iodide is destroyed by boiling the solution with concentrated HSOa before the extraction of palladium. The interference of SzH4 is eliminated by extracting it with salicylaldehyde from acid solution. Nature of the Extracted Species. The extraction of yellow color into nonpolar organic solvents suggests t h a t palladium(I1) is probably extracted as a neutral species into the organic phase. The composition of the extracted species has been determined by Job’s continuous variation method (2, 3 ) . The curve (Figure 2) obtained by plotting absorbance against R (1-01. of Pd soln./vol. of Pd soln. vol. of H I S A S soln.) shows two maxima at the points corresponding to H1NAA:Pd equal to 1:l and 2 : 1, which are independent of concentrations of reactants and the wavelength of the light employed. The reaction of HINAX with palladium may therefore be represented as follows:
+
+ HINAA f Pd(ISA.4) + H + Pd(I?;-&A) + HIXAA + Pd(1Srlh)z + H + Pd-2
+
+
The yellow color extracted into CCll from solutions containing palladium
and excess of HINXA is due to a neutral chelate, Pd(IKAA)?. Precision, Accuracy, and Sensitivity. The precision and accuracy of the proposed method were tested by analyzing solutions containing known amounts of palladium according to the recommended procedure. The average of 10 determinations with 5.00 pg. of P d per ml. is 5.01 pg. and it varies between 5.07 pg. and 4.96 pg. at 95% confidence limit. The practical sensitivity of the method is 1.5 pg. of Pd per ml. of solution. However, the sensitivity can be increased by volume concentration techniques. ACKNOWLEDGMENT
Our grateful thanks to A. B. Kulkarni, Institute of Science, for providing facilities to use the Hilger and Watts ultraviolet spectrophotometer. The authors also express thanks to James R. DeVoe, U. S. National Bureau of Standards, for his constructive comments on the original manuscript. LITERATURE CITED
(1) Feigl, F., “Chemistry of
Specific, Selective and Sensitive Reaction,” R. E. Oesper, transl., p. 209, Bcademic Press, New York, 1949. (2) Irving, H., Pierce, T. B., J. Chem. SOC. 1959, 2965. (3) Job, P., Ann. Chim. 9, 113, 1928.
Table II. Masking Agents Required to Suppress the Interference by Other ions
Interfering ions
Masking agents added Mercuric nitrate Ammonium molybdate Tartaric acid Sodium fluoride Potassium sulfate Ferric chloride Sodium molybdate hydrogen peroxide f sulfuric acid
+
N.J., h1.S~.thesis, University of Bombay, India, 1965. (5) Sandel!, E. B., “Colorimetric Determination of Al‘etals,” Interscience, Kew York, 1959. (6) Taylor, T., EqFbank, E., J . Chem. Xoc, 1926, 2819. (7) T’ogel, 8. I,, “Textbook of Quantitative Inorganic Analysis,” Longman’s Green Pvt. Ltd., London, 1962. (8) Welcher, F. J., “Organic Analytical Reagents,” Vol. 111, p.2 80, Van Nostrand, Kew York, 1955. (4) Patel,
U. B. TALWAR B. C. HALDAE
Inorganic and Nuclear Chemistry Laboratory Institute of Science Bombay, India WORKsupported by Grant PL 480, U. S. National Bureau of Standards, and a research scholarship (E. B. T.), University Grants Commission, India.
Analysis of Diaminotoluene Isomer Mixtures by Nuclear crg netis Resonance Spectrometry SIR: The diaminotoluenes (D.A.T.’s) are important commercial compounds. They are intermediates in several largescale manufacturing processes-e.g., in the production of polyurethane foams where large quantities of toluene diisocyanates are prepared from the diamines. The diamines themselves are normally obtained by reduction of the dinitrotoluenes (D.N.T.’s) produced by direct nitration of toluene under allpropriate conditions. The nitration gives a mixture of isomers, mainly 2,4and 2,6-D.N.T. with smaller amounts of 2,3- and 3,4-D.N.T. and possible traces of the 2,5-isoniera When the D.K.T.’s and D.A.T.’s are process intermediates, it is often important t o know the isomer proportions, but hitherto no satisfactory single method has been available for a full quantitative analysis. For the D.A.T.’s, isomer content information can be obtained by a coinbination of several methods. Reaction with acidified SaNOz followed by ultraviolet examination of the resulting bisdiazonium derivatives can give the ratio
of 24- to 2,6-isomers. The standard colorimetric test, using a diketone to give the o-diamine content, determines the sum of the 2,3- and 3,4-isomers. The colorimetric test with iron(II1) chloride gives the p-diamine content arising from any 2,6-isomer. However, it has been shown (2) that D.K.T. isomer mixtures can be analyzed by nuclear magnetic resonance (NXR) using the fact that the methyl proton resonances of all the isomers are slightly separated in CDCls solution. This same approach has now been tried for the diaminotoluenes. Each of the three chemical methods mentioned above is able to give results for part of the isomer analysis more accurately than NILIR. However NMR gains by giving a quick and convenient method of analysis of all four main components with an accuracy sufficient for most; purposes. EXPERIMENTAL
Apparatus. A Varian A.60 spectrometer was used with tetramethylsilane as an internal reference. Chemical
shifts are quoted in 6 units-Le., p.p.m. downfield from T.M.S. Chemicals, 99.5% CDCh was obtained from Ciba (A.R.L.) Ltd. Samples of the diaminotoluene isomers were available elsewhere in this Department and the N M R spectra themselves were used as a check for impurities. RESULTS AND DISCUSSION
Reference spectra in CDC13 were obtained for all the D.A.T.’s with the exception of the 3,5-isomer, which is not found in the systems under discussion. The results are given in Table I for 20% w./v. solutions. I t can be seen that a full analysis using the aromatic proton signals is not possible. The ratio of the 2,4- and 2,6-isomers can be obtained, but the substituent chemical shift parameters (1) predict little difference in the shift positions of all the aromatic protons in the 2,3-, 2,5-, and 3,4-isomers, and one overlapping set of signals is found experimentally for these minor components. For the 2,4- and 2,6-isomers where the aromatic proton signals are more widely VOL. 38, NO. 13, DECEMBER 1966
e
1931
