Comparison of several liquid phases in gas liquid chromatography of methyl parathion and metabolites

Abstract

Adequate gas chromatographic separation is primarily dependent upon the proper selection of liquid (stationary) phases, with right selection based on trial and error and experience. Additionally, to avoid base-line drift and bleeding, only those phases which are nonvolatile in the region of the operating temperature can be considered. Therefore, in gas chromatography, the ability to vary the nature of the separation of a multi-component mixture is largely dependent upon the use of thermostable liquid phases which have different chemical structures and which show selective retention effects for different compounds. Brown (i) has classified liquid (stationary) phases as non-polar, electron acceptor, and electron donor, but they can be additionally categorized as dipole-dipole interactors (2). Such classifications are oversimplified since the retention of the solute is governed by the individual solute-solvent interactions, and several interactions may be operating simultaneously. The popular classification of phases as polar and nonpolar, however, has much to commend it. The polarity of a stationary phase is ~related to its polar or polarizable groups. A general ruleof thumb is that the greater the polarity of the stationary phase, the greater the retention of a polar solute relative to that of a nonpolar solute. In this laboratory, we have been attempting to build up background information for the determination of organophosphorus compounds by glc. The present contribution compares different liquid phases in their ability to separate methyl parathion from its metabolites.