ONLINE MICROPOROUS MEMBRANE LIQUID-LIQUID-EXTRACTION FOR SAMPLE PRETREATMENT COMBINED WITH CAPILLARY GAS-CHROMATOGRAPHY APPLIED TO LOCAL-ANESTHETICS IN BLOOD-PLASMA

A new automated procedure for analyzing complex samples has been devel oped utilizing microporous membrane liquid-liquid extraction (MMLLE) c ombined with capillary gas chromatography. Some local anaesthetics wer e used as model compounds in aqueous solution as well as in blood plas ma. The MMLLE procedure was performed in a now system with the sample fed to the donor side of the hydrophobic microporous membrane and with an organic solvent (hexane) in the pores and as the acceptor solution . The analytes in a small volume of sample (<1 mt) were extracted into the organic acceptor phase which was transferred into the gas chromat ographic system by utilizing a loop-type interface compatible with lar ge-volume (300 mu L) injection. High selectivity and low carry-over ef fects were obtained with the system. The detection limits were 0.5-1 n g/mL using 0.5 mt of human plasma, and the precision was similar to 5% . The effects of pH, now rates, and adsorption of the analytes were ev aluated.