Trace analysis by combined use of off-line solid-phase extraction, on- column sample focusing and U-shape flow cell in capillary liquid chromatography

Abstract

The potential of capillary liquid chromatography for routine analysis of trace environmental pollutants was demonstrated in the determination of four polycyclic aromatic hydrocarbons (PAHs) at sub-ppb levels in natural water. The method involved the quick conversion of conventional high- performance liquid chromatography capillary LC using a commercially available upgrading kit. Focus was placed on enhancing concentration sensitivity by the combined use of off-line solid-phase extraction (SPE), on-column sample focusing and a U-shaped capillary flow cell. Influencing factors in SPE (sample volume, sorbent, eluent and elution temperature) and sample focusing (injection volume and sample solvent) were investigated together for optimizing overall enrichment. Under optimal conditions, the detection limit was in the range of 0.04-0.2 μg/l for the four PAHs. Sample volume was reduced, evaporation of organic eluent was eliminated, and therefore total analysis time was reduced; recoveries for the PAHs were >84%.