A Convenient Method to Obtain
Samuel J. Costanso University of N e w Hampshire Durham, 03824
Preparative Samples by GLC
Almost since the beginning of the use of gas chromatography as an analytical tool for research, preparative chromatography has found wide application. I n analyzing a reaction mixture it is often necessary to have only enough material to permit the running of various spectra. In order to facilitate this goal, various traps have been devised for the purpose of collecting samples directly from a gas chromatograph. However, these traps are generally somewhat time consuming to build and/or inefficient in terms of amount of sample recovery. The author has found that a simple and efficient collecting device may be made by a small adaptation of the collection outlet found on the Varian-Aerograph gas chromatograph (Model 90-P). A disposable pipet (Fisher Scientific Co. 13-67815) is cut with a file so
Recovery Efficiency of Liquid Samples from Preparative Gas Liquid Phase Chromatography
Sample benzene 1-butanol water ethylene bromide
Boiling point
Percent
xn
35 37 40
('C, 760 mm) recovered
75
that the long thin stem is removed from the upper portion. The stem of the pipet is then placed on the end of the collection outlet by unscrewing the Teflon fitting and removing the piece of the metal tubing (see figure). I t was found convenient to collect the s a m ~ l e directly into a standard nuclear magnetic reasonance tube, cooled by a Dry Ice-acetone bath. As the gas travels through the pipet stem, it begins to condense, and the sample is then trapped in the nmr tube. The Teflon fitting and the pipet stem may easily be removed after the desired peak has been collected. Alternatively, the liquid sample can be collected on a salt plate if only infrared analysis is desired. The advantage of having the gas condense on the inside of the pipet stem is that it prevents fogging caused by direct cooling of a hot gas. Several samples, with a wide range in boiling points, c were passed through an SAIB column (10 f t X '/a in.) at 170°C with a helium flow of 50 ml/min. The percent of sample recovered is listed in the table. Collodion opparatm. A, Gar The author wishes to chromdography; 8, collection outlet; C, teflon fittingi D, d i r thank Dr. R. for his helpful comments. poroble pipet.
Volume 47, Number I , January 1970
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