Gas chromatographic analysis of organic compounds on non-polar adsorbents

Abstract

The applicability of new non-polar adsorbents in gas chromatography has been investigated. Molybdenum and tungsten sulphides are characterized by a lamellar structure, which resembles the structure of graphite, and hence are expected to show chromatographic properties similar to those of graphitized thermal carbon black (GTCB). This assumption was verified chromatographically by comparing the properties of argon plasma-treated thermal carbon black (TCB) with the properties of MoS 2 and WS 2 and MoSe 2. The adsorption characteristics (relative retentions, heats of differential adsorption) were determined at low levels of adsorbent surface coating with reference compounds. The results indicate that the treatment of TCB in a hydrogen-containing plasma (oxygen-free flow) results in lower retentions. The retention of n-alkanes by MoS 2 and WS 2 is higher than that of monoalkylbenzenes with the same number of carbon atoms. Di- n-butyl ether is adsorbed by MoS 2 and WS 2 more weakly than n-nonane, which indicates a homogenous sorbent surface. The adsorption of di- n-butyl ether on MoSe 2 is stronger than that of n-nonane, which indicates an non-homogeneous adsorbent surface. The results made it possible to derive several practically applicable conclusions. MoS 2 and WS 2, for instance, can be used for analytical purposes at lower temperatures than thermal carbon black. The adsorbents under consideration are suitable for the separation of structural and geometrical isomers.