Table Ill.
Dodecylammonium Chloride Analysis
Concn. of dodecylammonium chloride, mg./liter
A
0.244 0.340 0.439 0.530
0,686
0,624
of the positive surfactant determinations is considered to be due to the lack of adsorption of bromphenol blue on the sintered-glass plate, the dye being removed easily after each float by washing with ethanol. The reproducibilities above agree favorably with those obtained in the dye method of Few and Ottewill (6), who obtained values of 1 2 % to 1 5 7 , at concentrations of 10-Pll.
Gregory (7) reported a relative standard deviation of approximately 1% for the determination of oleic acid in a 4.74 p.p.m. solution. This author reports, however, that when lauric acid was investigated, much lower recoveries were obtained. The results for determining dodecylammonium chloride in the concentration range 0 to 5 mg./liter are shown in Table 111. This calibration curve tailed off a t low concentrations, which could be due to a small amount of inherent surface activity of the bromphenol blue. The calibration curves above were prepared over the concentration range 0 to 50 mg./liter (0 to f 2 X 10-41V) because this was convenient for the analysis of the unknown solutions used. However, calibration curves over greater concentration ranges can be prepared by increasing the amounts of dye added. For calibration curves over smaller concentration ranges, attention must be paid to variables such as float time and gas flow rate which become important.
LITERATURE CITED
( I ) Brown, -4.S.,et al., J . Phys. Chem. 56, 701 (1952). ( 2 ) Burger, X., 2. Anal. Chem. 196, 15 i1962). \ - - - - I -
(3) Chen, D. T. Y., Laidler, X. J., Can. J . Chem. 37, 599 (1959).
(4) Cushman, A., Brady, A. Pa,McBain, J. W., J . Colloid Sci. 3, 425 (1948). ( 5 ) Fern, A. V., Ottewill. R. H.. Ibid.. 11, 34 (1956).‘ ( 6 )7Finar, I. L., “Organic Chemistry,” 101. 1, 759, 3rd ed., Longmans, London. 1959.
(7) G&ory, G. R. E.C . , Analyst 91, 251 (1966). 3) Ralston, A. W.,Hoerr, C. W., J. Am. Chem. SOC.64, 772 (1942). 3) Sebba, F., “Ion Flotation,” 1st ed., Elsevier, Amsterdam, 1962. 10) Tamamushi, B., Tamaki, K., Trans. Faraday Soc. 5 5 , 1007 (1959). 111 Tomlinson. H. S.. Sebba., F.., Anal. Chim. Acta 27, 596 (1962). IT.&I. LOVELL FELIXSEBBA Chemistry Department Universit of the Witwatersrand Johanneszur g Financial assistance to V. RI. Love11 from the Kational Institute for Metallurgy, Johannesburg.
Direct Gas Chromatographic Determination of Isopropyl N-( S c h lorophe nyl)ca rb a mate (CIPC) SIR: An analytical method was required for determination of the herbicide, isopropyl N-(3-chlorophenyl)carbamate (CIPC). This material may be encapsulated to facilitate its controlled release into the soil. Since various experimental materials and conditions are used in preparing the encapsulated herbicides, a rapid analytical procedure to determine CIPC mas needed. Most methods for pesticide analyses deal with trace quantities of material, thus requiring extremely sensitive detecting devices-e.g., colorimetric, hydrogen flame, or electron capture. The prime consideration of this method is the determination of the encapsulated herbicide at levels of 50 to 7570 CIPC. Methods available in the literature make use of the acid hydrolysis of the phenyl carbamate with subsequent colorimetric analysis of the resultant aniline derivative (1,S). The method of Gutenmann and Lisk ( 2 ) utilizes a gas chromatographic separation with electron affinity detection of the brominated hydrolyzate of CIPC. An attempt a t the direct chromatographic separation of the CIPC was made in the hope of obtaining a onestep analysis of the extracted herbicide. Initial experiments using packed columns of 2 meters or more and temperatures exceeding 230’ C. caused degrada1928
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ANALYTICAL CHEMISTRY
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I
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Figure 1.
3
4
5
6
7
TIME ( MINUTES 1 Chromatographic separation of CIPC
tion of the CIPC. The resulting chroEXPERIMENTAL matograms contained many peaks of the Apparatus. A gas chromatograph pyrolytic products of the material. equipped with a tungsten wire thermal By lojvering the operating temperature conductivity detector was constructed in the laboratory and used for the below 2000 C, and using a 4-foot by 1/4-inch with 15% ~ ~ 3 3 0 analyses. Chromatogranls were recorded on a Leeds and Worthrup on Chromosorb IT, separation of the Speedomax H recorder 0- to l-mv. CIPC was attained without apparent response, ~h~ column used was a pyrolysis. Precision and linearity of 4-foot by l/4-in& aluminum tube concentration versus detector response packed in the usual manner with 15% were good as is shown in the results. SE30 on Chromosorb X, 60/80 mesh.
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
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