TRACE ENRICHMENT OF ENVIRONMENTAL-SAMPLES IN CAPILLARY ZONE ELECTROPHORESIS

Environmental ultra-trace analysis of aqueous samples can be successfu lly performed using capillary zone electrophoresis (CZE) provided that a suitable focusing injection technique is used. Emphasis is put on t he injection and preconcentration of very large sample volumes using t he field-amplified injection method. Sample pretreatment can be minimi zed by using C18 membrane disks for simultaneous filtering and solid p hase extraction. Desorption from the disks directly into the CZE sampl e vials can be carried out using acetonitrile-buffer mixtures, thus pr oviding a sample matrix having a sufficiently low and constant conduct ivity. The potential of this approach for environmental trace analysis is clearly demonstrated by the determination of phenoxy acid herbicid es, as model compounds, in drinking- and river-water samples at the su b-ppb level.