Comparison of Support-coated Open Tubular, Wall-coated Open Tubular, and Packed Liquid Crystal Columns for the Gas-Liquid Chromatographic Analysis of Polycylic Aromatic Hydrocarbons

Abstract

A gas chromatographic comparison is made between packed, support-coated open tubular, and wall-coated open tubular columns coated with the liquid crystals N,N'-bis (p-butoxybenzylidene) -α, α'-bi-p-toluidine (BBBT) and N,N'-bis(p-phenylbenzylidene)-α,α' bi-p-toluidine(BPhBT) in terms of their resolving power, analysis time, detection limit, and thermal stability for the analysis of polycyclic aromatic hydrocarbons (PAH) present in the environment. This study indicated that the BPhBT packed column best fulfilled these criteria. The BBBT packed column required a longer analysis time, since BBBT is a lower temperature liquid crystal, without giving any additional benefits. The SCOT columns gave the lowest detectable limit, but the resolution obtained, time of analysis, and thermal stability were poor. The WCOT columns showed good resolution, minimum detectable limit, and thermal stability for the BBBT stationary phase. The analysis time, however, was long. The BPhBT WCOT columns were not thermally stable at temperatures above 260℃. Suggestions for improving SCOT and WCOT columns containing liquid crystals are also given along with earlier chromatograms showing that these columns are useful for separating complex mixtures. Their reproducibility, however, is poor. Overall it was found that using the above columns, complex PAH mixtures can be separated with better resolution than on conventional phases.