Sampling Valve for Use in Gas Chromatographic Analysis of the Products of Gaseous Reactions G. L.
Pratt and J. H. Purnell, Department of Physical Chemistry, University of Cambridge,
Lensfield Road, Cambridge, England
I"t o
kinetic studies it was necessary remove vapor samples directly from a vacuum system for injection into a gas chromatographic analysis unit operating at high colunin inlet pressures. It was desired t o make these samples as small as possible in order not t o affect the reaction significantly, and their size was, therefore, determined only by the sensitivity of the detector system. I n view of the small sample size, the high pressures involved, and the fact that much of the material was condensable, both hypodermic methods and valve systems containing lubricant were unsuitable. Experience showed that no sampling system available commercially or described in the literature was either likely to give. or did give, satisfactory results. I n particular, the maintenance of a good vacuum and a very high gas pressure across the sampler presented formidable problems which w r e accentuated b y the need to heat the system t o about 150" C. Subsidiary problems to be overcome were the nerd for a negligible dead volume between the sampler and the reaction vessel, and alqo within the sampler itself; also, the operation should be rapid. This work describes a sampler designed to meet the above specification
