AUTOMATED-SYSTEM FOR THE TRACE ANALYSIS OF ORGANIC-COMPOUNDS WITH SUPPORTED LIQUID MEMBRANES FOR SAMPLE ENRICHMENT

Supported liquid membranes, mounted in flow systems, can be used for s elective and efficient extraction and enrichment of various types of a nalytes. The basic principle is a continuous extraction from an aqueou s phase into an organic solvent, immobilized in a porous hydrophobic m embrane, followed by a continuous back-extraction to a stagnant aqueou s acceptor phase on the other side of the membrane. The entire accepto r phase is then used for further analysis. The ASTED (Gilson) automate d sample preparation system was modified by exchanging the dialysis un it for a supported liquid membrane unit. This permits a direct connect ion to a liquid chromatographic column with minimal sample losses. The instrument can be loaded with up to 60 samples, which are automatical ly processed before the final chromatographic analysis. With this equi pment, the same sample can pass the membrane extractor several times ( while the acceptor phase remains stagnant) to give a higher recovery. When one sample is chromatographed the next one is enriched simultaneo usly. The technique was evaluated for the extraction of a basic drug a nd its metabolite from water solutions with the purpose to be applied to brood plasma samples. The recovery depends on the time used for the enrichment. With enrichment times similar to the chromatographic run, or ca. 15 min, the recovery was ca. 35%.