The use of precolumn reactions for the selective removal of compounds bearing alcohol or carbonyl functional groups in the gas chromatographic analysis of mixtures

Abstract

The use in conjunction with gas chromatography of 3-nitrophthalic anhydride and semicarbazide as reagents for selectively subtracting alcohols and carbonyl compounds, respectively, from mixtures containing these compounds was investigated. Each reagent, when deposited on a diatomaceous earth support and heated as a short plug in the injection block of a gas chromatograph, either removed or markedly reduced the peaks due to a large number of compounds bearing these functional groups. These short precolumns were amenable to operation with glass porous layer open tubular analytical columns under temperature-programmed conditions for compounds covering a moderate range of boiling points without seriously affecting the performance of the columns. The performance of the above reagents was compared with a number of other compounds cited in the literature as specific abstractors, viz., boric acid for alcohols, free fatty acid phase and o-dianisidine for aldehydes and benzidine for aldehydes and ketones. These compounds were tested both as short-heated precolumns and also when coated on lengths of porous layer open tubular columns in the manner of normal liquid phases.