On-line Sample Pretreatment Based on Membrane Enrichment, Mainly Using Supported Liquid Membranes, for Chromatographic Analysis

The main objective of this work was to construct practical analytical systems for the analysis of environmental and biological samples, using membrane-based techniques for sample pretreatment and chromatography for final analysis. Two types of membrane processes have been applied, with emphasis on automation. The supported liquid membrane (SLM) extraction was carried out in an automated continuous flow system coupled to ion-exclusion chromatography (IEC) for the determination of volatile carboxylic acids in air. Another totally automated system, using the SLM coupled on-line to anion-exchange chromatography, was developed for the determination of low-molecular weight organic acids in soil samples. Several short precolumns were co-ordinated with the SLM enrichment system to remove interfering compounds. The system has been used for routine measurements. The SLM extraction was combined with capillary gas chromatography (GC) for the determination of local anaesthetics in untreated blood plasma samples. A solid phase column was located between the SLM unit and GC unit as a interface for phase switching. The system was fully automated and permitted the analysis of ca 50 samples per day. Microporous membrane liquid-liquid extraction (MMLLE), combined with capillary GC quantitation, was presented for treating complex samples. The local anaesthetics were used as model compounds both in aqueous solutions and in blood plasma. The method can be used for routine measurements of the analytes in plasma at sub ppm level. In this thesis, a general overview of different membranes and membrane processes, in particular SLM, and their applications of sample preptreatment are given. The applications of membrane-based sample preparation for on-line coupling with liquid chromatography and gas chromatography are discussed. Finally a brief discussion about automation of analysis is given