ONLINE SUPPORTED LIQUID MEMBRANE LIQUID-CHROMATOGRAPHY WITH A PHENOL OXIDASE-BASED BIOSENSOR AS A SELECTIVE DETECTION UNIT FOR THE DETERMINATION OF PHENOLS IN BLOOD-PLASMA

The potential of on-line combination of supported liquid membrane extr action and column liquid chromatography with a phenol oxidase-based bi osensor as a selective detection unit has been investigated for the de termination of phenols in human plasma. The phenols are selectively ex tracted into a porous PTFE (polytetraflouroethene) membrane impregnate d with a water-immiscible organic solvent and further into an alkaline acceptor phase. Via an ion-exchange interface, the analytes are trans ferred to a reversed-phase column where they are separated and detecte d using the biosensor. No sample pretreatment before the extraction, e xcept centrifugation, is made. Due to the high selectivity both in the extraction and in the detection steps and to the fact that the demand s on the chromatographic separation are low, a quick separation using an eluent with a low concentration of organic modifier can be made, wi thout affecting the biosensor response. Detection limits below the 50 mu g/l level in blood plasma were obtained for the three model compoun ds, phenol, p-cresol and 4-chlorophenol. (C) 1997 Elsevier Science B.V .