Technique for removing water from moist headspace and purge gases containing volatile organic compounds. Application in the purge with whole-column cryotrapping (P/WCC) method

Abstract

Volatile organic compounds (VOCs) are easily removed from water by use of an inert purge gas. VOCs are therefore easily determined by the purge with whole-column cryotrapping (P/WCC) method. In P/WCC, purging takes place directly from a sample to a capillary gas chromatography (GC) column while the latter is maintained at a cryotrapping temperature. Water vapor is purged to the column along with the analytes. The water can cause variability problems with the GC retention times and responses. A water trap technique is described that reduces the amount of water in VOC-containing gas streams. The technique involves passing most of the purge gas stream through a short column of glass beads at {minus}10{degree}C. Analytes collected in the trap are quantitatively transferred to the GC column in a final short purge of the trap carried out at ambient temperature. Desiccation efficiencies of 90% can be obtained without any loss of analytes.