atmosphere, and .If ia the molecular weight of the oil. Thut;,
e cc. per second
=
MPVA-/RTtd
(2)
N may be found by dividing the peak area of silicone oil by the sum of the peak areas of the silicone oil and air (and trichloroethylene if present). Neglecting the area of the trichloroethylene peak introduces only a 2out 1% error in the final result. Constant factors in Equation 2 were collected as shown in Equation 3.
Gsing Equation 3 ttnd the data in Table I, the results shown in Table I1 were calcula’ted. The main limiting factor of sensitivity in this technique is the length of time the container remains inside the evacuated sample chamber. Using representative values of 45 mm. of Hg pressure for 20 minutes yields a leak-?ate accuracy of 10-9 cc. pcr second. Using 200 minutes
will increase the limit another order of magnitude, which is sufficiently sensitive to detect leaks as small as 1 cc. per 30 years. Obviously the surface of the container in question and the sample chamber must be free of residual DC 200. Any containers which are silicone oil or liquid filled may be leak tested by this technique, provided the liquid can be partially vaporized at temperatures below the working temperature of the column used, 175” C. For higher temperatures, different columns must be used. The results gathered in this work show that this technique is valid and yields more meaningful data for a liquid leak test than does the helium or Radiflo tests. This leak-detection method is applicable to all components, both electrical and mechanical, that must be stored for extended periods of time, and which, after storage, must perform properly. These components may be filled with any volatile liquid or a n y gas. Thus, the chromatographic leak-detection
method is applicable for both gas and liquid leak-rate determinations. There are several acceleration-sensing and integration devices used in the aerospace and missile field that are leak checked using this method. ACKNOWLEDGMENT
The authors express their appreciation to B. T. Kenna for his assistnnce in preparing this paper. LITERATURE CITED
(1) Bannister, D. W., Phillips, C. S. G.,
Williams, R. J. P., ANAL.CHEM.26,
1451 (1954). (2) Cropper, F. R., Heywood, A,, Y a t i o e 172, 1101 (1953). (3) Zbid., 174, 1063 (1954). (4) Glasstone, S., “Textbook of Physical Chemistry,” p. 193, Van Sostrand,
Kew York, 1958. (5) McCormick, H., Analyst 78, 562 (1953). RECEIVEDfor review May 20, 1963. Accepted July 22, 1963. This work was performed under the auspices of the United States Atomic Energy Commission.
Gas Chroima tog ra phic Ana lysis of ChIo rophe n o I Mixtures R. H. KOLLOFF, L. J. BREUKLANDER, and L. B. BARKLEY’ Monsanto Chemical
Co., 800
North lindbergh Blvd., St. louis 66, Mo.
b The use of a phosphoric acid additive and a thermally stable substrate capable of forming :,trong hydrogen bonds a t elevated temperatures makes possible the determination of free chlorophenols on on3 GLC column without sample pretreatment. The ortho effect is successfully applied to obtain the necessary retention time reversals for resolution of phenol and eight chlorophenols. Double peak formation is observed for the first time in a nonaqueous systern.
T
numerous approaches to the analvris of mixtures of chlorophenols include infrared spectrometry ( 6 ) , nonaqueous spixtrophotometric titrations ( 7 ) , ion exchange chromatography ( I S ) , and gas liquid chromatography (1, 2, 5 , l 4 ) . Of these techniques the titrimetric method ( 7 ) is the least promising, being limited to relatively simple mixtures of knoan components in roughly equal amounts. Ion exchange (13),while giving good resolution of most of the chlorophenols, requires 3 HL
Present address, Pennsylvania Industrial Chemical Corp , Clairton, Pa.
to 4 hours for a qualitative determination of o-chlorophenol (OCP), 2,4dichlorophenol (2,4-D C Pj , 2, 6-dichlorophenol (2,6-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP), with quantitative work requiring still more time. Phenol and p-chlorophenol (PCPj are not determined. Infrared spectrometry (6) is versatile and will give a complete analysis of comples mixtures of chlorophenols, but sensitivity and precision are limited, a large number of standard curves are required, and the calculations are laborious (graphical solution of simultaneous equations by succesbive approximation). Gas chromatography offers a simple, rapid, and sensitive method of analysia but t o date has suffered major drawa lack of suitable subbacks-e.g., strates with high temperature stability, poor resolution, and tailing of the chlorinated phenols on many polar substrates. Extensive gas chromatographic work on alkyl-substituted phenols has been done ( 2 , 3, 8, 9, 11, 12), but extension of the techniques to chlorophenols has been relatively unsuccessful. Fitzgerald (2) recommended sample pretreatment (methylation) and GLC
analysis of the chlorinated anisolcs, rather than direct determination of the chlorophenols, particularly when the 2,6- and 2,4-DCP isomers were to be separated. Harvey and Xorman ( 5 ) also used sample pretreatment (titration with diazomethane) and stated that mixtures of chlorophenols could not be analyzed directly. Barry, Vasishth, and Shelton ( I ) did analyze chlorophenols directly, but for mixtures containing PCP, 2,4-DCP, and 2,6DCP, two different GLC columns (polar and nonpolar) and two separate analyses were required. In addition, 2,6-DCP was not completely resolved from 2,4-DCP but rode on the 2,4-DCP tail. In the method described below, 2,6DCP is clearly resolved from and is eluted before 2 , 4 D C P , despite its higher boiling point. Because of this position reversal, it is possible for the first time to determine small amounts of 2,6-DCP in 2 , 4 D C P quickly and accurately (Figures 1, 2, and 3). Complete resolution of eight chlorophenols and phenol can be obtained directly on one column (Figures 1 and 2 ) , and no sample pretreatment or additional analyses are required. h phosphoric VOL. 35, NO. 1 1 , OCTOBER 1963
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