Determination of volatile sulphur compounds in air at the parts per trillion level by Tenax trapping and gas chromatography

Abstract

A gas chromatographic technique is described for measuring various volatile sulphur compounds (H2S, COS, CS2, thiols, sulphides, disulphides) in air at the parts per trillion level. The sulphur compounds are trapped and concentrated at -196 degrees C in a small glass tube filled with the porous polymer Tenax GC. The excess of water in the air samples is pretrapped by calcium chloride, which drying agent does not adsorb any of the sulphur volatiles. The Tenax trap tube fits exactly in the injection port of the gas chromatograph, where the adsorbed sulphur compounds are liberated at 200 degrees C directly into the carrier gas stream and are transferred to the gas chromatographic column. The sulphur compounds are then assayed by means of a flame photometric detector. The Tenax trap tubes can be stored at -196 degrees C for more than 1 week without any loss of sulphur volatiles.