DRYING AGENTS FOR WATER-FREE INTRODUCTION OF DESORPTION SOLVENT INTO A GC AFTER ONLINE SPE OF AQUEOUS SAMPLES

A small cartridge containing a drying agent is inserted between a solid phase extraction (SPE) column and a gas chromatograph (GC) to enable the introduction of water-free desorption solvent into the GC in on-line liquid chromatography (LC)-type enrichment of trace-level analytes from water samples. Some characteristics of the drying agents, such as their capacity to retain water and their re-usability after heating, have been tested. Possible interactions of the drying agent with the analytes, e.g., irreversible adsorption or catalyzed degradation, have been checked for a wide range of alkanes, alkylbenzenes, chlorobenzenes, chlorophenols and phthalate esters. Using the on-line SPE-GC system with flame ionization detection (FID) and spiked samples containing different levels of the test compounds, the repeatability was shown to be satisfactory (6-17 %). For 10 mL samples, the detection limits were lower than 0.1 mu g/L. The on-line SPE-GC-FID system here presented can be used for the repeated analysis of water samples without exchange of the drying cartridge. The technique is applied to the analysis of tap water.