Analysis of Aqueous Solutions by Gas Chromatography

tions exceeding 0.1F could not be pre- ... and aliquots transferred at temperatures below 0°. The reaction is so slow in ... interval of approximatel...
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results in an undesirable partial vacuum (1).

CHBRACTERISTICS O F CHROMIUM CHLORIDESOLUTIONS.The solubility of CrClZin DNF is such that concentrations exceeding 0.1F could not be prepared a t room temperature. Chromium (11) solutions, even when in contact with solid CrC12, decreased in titer when exposed to light; and in solutions not in contact with solid reagent stored and delivered as described, the decrease in concentration was approximately 0.2% per 24-hour interval over a period of more than 40 days. Whenever unsteady voltage readings constituting a definite drift from the Cr(III)/Cr(II) half cell were observed, results corresponded t o considerable more titrant than was needed for equivalence. This seemed to result from air oxidation because of insufficient nitrogen in the atmosphere of the titration. PROCEDURE. Stock solutions of samples were titrated less than 4 hours after preparation except in the cases of CuClz 2 H z 0 and 12,which were used as primary standards and prepared on the day of use. After the samples of solution had been prepared as stated in the Tic13 reductions, the cap of the titration vessel was replaced with a ground glass sleeve. The indicator electrode was inserted in the sleeve and tubing bearing a nitrogen stream forced well into the lower part of the sleeve near buret stem and electrode. More than 90% of titrant required for equivalence was added, then stirring was begun and continued throughout the titration except when voltage readings were taken in cases of Br2 and TiCL solutions. Analyses and preparations of solutions of Cu(II), Iz, Fe(III), Brq, and Sb(V) are identical with those above. Titanium(1V). The Fisher Scientific Co. product was reported b y the manufacturer to contain 99.8% Ticla. Results obtained b y precipitation of the hydroxide and ignition to TiOz (100.3 f 0.1% TiC14) were in excellent agreement. The Tic14 solvated violently in DRIF, and transfer without considerable and prolonged fuming could not be

made. To prepare a stock solution. a 100-ml. volumetric flask was filled with nitrogen and weighed; D l I F was added, the flask reweighed, then cooled to less than 0" in an ice-salt bath and opened in a nitrogen stream. Then a t least 1 gram of TiCl4 was added quickly by pipet and the solution shaken well. The flask was weighed approximately, wiped, then quickly weighed carefully. Stock solutions were stored in the dark. Iodine Xlonochloride. Iodine monochloride was analyzed iodometrically to contain 100.7y0 reducible substances calculated as IC1. Transfers of IC1 were made in glass ampoules having very thin capillary arms; capillaries as well as ampoules were crushed in preparing solutions in DMF.

perienced in locating the equivalence points. But when ampoules containing SbCl6 were thoroughly crushed by a quartz rod inserted in closed vessels (fitted with Quorn sleeves) containing D M F and the solution was immersed in a M e O H 4 r y ice mixture, no perceptible end points or uncertain ones were obtained. The SbCla content was invariably low. I n the titration of TiC14, it is important that true equilibrium be attained after the addition of the first (more than 90%) portion of the CrC12. This reaction is slow in the vicinity of the end point; 30 seconds may be necessary for obtaining a steady voltage reading. LITERATURE CITED


The results of typical titrations are in Tab!e 11. Neither experimental errors in volumes transferred nor in sample weights taken incurred errors of as much as 1 part per thousand. All reactions are essentially instantaneous during the whole course of a titration except as stated below. The titrations of Cu(II), Izr Fe(III), and IC1 were without complication or distinguishing feature. Low results were obtained when Br2 solutions were prepared and titrated a t room temperature. More accurate results were obtained when stock solutions were made and aliquots transferred at temperatures below 0". The reaction is so slow in the vicinity of the end point t h a t a n interval of approximately 10 seconds may be necessary for equilibrium to be approximated. Upon addition of the volume increment required t o reach equivalence, a drift in potential toward that of the Cr(III)/Cr(II) half cell is observed for the first time. Table I1 shows that excellent precision was obtained in the titration of each individual SbCls solution prepared as stated above; no difficulty was ex-

(1) Du Pont Product Information Bull., A-aOllj, April 1, 1954. (2) Hinsvark, 0. S . , Stone, I(. G., AXAL.CHEM.27,371 (1955). (3) Ilinsvark, 0. N., Stone, I(.G., Ibid., 28,334 (1956). (4) Nellor, J. W., "A Comprehensive Treatise on Inorganic and Theoretical Chemistry,'] Vol. IX, p. 487, Longmans, Green, New York, 1929. (5) Tomicek, 0.)Chem. l i s t y 44, 283 (1950). ( 6 ) Tomicek, 0.) Sbornik celostdtni pru-

covn?. konf. anal. chemiku, 1st Conf. Prague I, 246 (1953). (7) Tomicek, O., Heyrovsky, J., Collection Czechslov. Chem. Communs. 15, 997


(8) FTatt, G. K., Choppin, G. R., Hall, J. L., J . Electrochem. SOC. 101, 229


(9) Watt, G. W.,Gentile, P. S., J . '4m. Chem. SOC.77, 5462 (1955). (10) Watt, G. W.,Hall, J. L., Choppin, G. R., Ibid., 73,5920 (1951). (11) Watt, G. K., Hall, J. L., Choppin, G. R., J . P h y s . Chem. 57,567 (1953).

(12) Watt, G. W.,Hall, J. L., Choppin, G. R., Gentile, P. S., J. Am. Chem. SOC. 76,373 (1954). (13) Willard, H. H., Boldyreff, A. IT., Ibid., 51, 471 (1929). RECEIVEDfor review March 27, 1961. Accepted July 10, 1961. Taken from a thesis submitted by James F. Hinton t o Temple University as partial requirement for the Ph.D.

Analysis of Aqueous Solutions by Gas Chromatography J. T. KUNG, J. E. WHITNEY, and J. C. CAVAGNOL Research Center, General Foods Corp., Tarrytown,

b Gas chromatographic analysis of solutions high in water on packed columns have been hampered seriously by the large tailing Of the water peaks. A technique has been develoDed usina an indeDendentlv heated precolumn calcium'carbide' to convert the water vapor to acetylene and eliminate.the effect of water entirely.


N. Y .

Recoveries from alcohol mixtures containing Over 90% water, and aidehydes, esters, and alcohol mixtures containing 36% water are excellent. Recovery Of 's lower but reproducible. Organic acids are retained b y the calcium oxide formed and cannot b e detected.

HE COMBINATION O f gas ChromatoT g r a p h i c and spectrophotometric techniques provides an excellent method of analyzing complex mixtures found in natural and synthetic flavors. The mixtures are separated by gas chromatography and the fractions trapped for subsequent identification by infrarea spectrophotometry or mass spectrom-

VOL. 33, NO. 1 1 , OCTOBER 1961



etry. Because of the relatively large sample size required for infrared analysis, packed colunins are rcquired for the separations. With systems high in water, which is common for many flavors, separations are very difficult because of the water tailing on the column and because water reacts with the liquid phase, thereby reducing the life of the column. Several authors have employed gas chrotnatographic analysis for aqueous solut'ions of organic compounds. Bodner and Mayeux ( 1 ) estimated low boiling oxygenated compounds employing triethylene glycol or polyethylene glycol 400 as the liquid phase. They were able to analyze the compounds which n-ere eluted before water. Zarembo and Lysyj (4) used a liquid phase of rlrmeen SD, a mixture of high boiling amines having a n average molecular weight of 297. They analyzed solutions of alcohols containing 25 to 7570 water. The components were separated on the amine as a function of polarit'y. Hence, water was eluted first follorved by ethanol, 2-propanol. I-propanol, 2but'anol, 2-methyl-1-propanol, and 1butanol. A. single chromatogram took about 1 hour with this substrate. Sundberg and Maresh ( 2 ) su1)stituted gas chromatography for the time-consuming microgravimetric procedure for carbon and hydrogen. after the combustion step, the gases were swept into a cold trap. The trap wne flushed with helium and the water vapor formed converted to acetylene by passing the gas through calcium carbide. The acetylene and carbon dioxide were separated in n silica gel c%olumnand detected with a thermal ronductivity cell. The method as significantly shorter than the conventional procedure. The purpose of this study was to remove water before the gas enterid the chromatographic column. This \\.as essent,ial t o extend the life of the column m d to reveal components that were mmked by the water peak. APPARATUS

Gas ('hromatograph, Burrell KromoTog, hIodel I