AUTOMATED SAMPLE PREPARATION USING SUPPORTED LIQUID MEMBRANES FOR LIQUID-CHROMATOGRAPHIC DETERMINATION OF SULFONYLUREA HERBICIDES

Sample preparation for determination of sulfonylurea herbicides in aqueous samples is investigated. The technique studied utilizes extraction and back extraction in an automated flow system and is coupled on-line to a liquid chromatographic system. The extraction unit consists of an immobilized liquid membrane, separating two aqueous phases. From the acidified donor phase the analytes are extracted into the organic solvent of the membrane. After traversing the membrane they are back extracted into an alkaline/neutral aqueous acceptor phase. They are trapped in the acceptor by dissociation, making them insoluble in the membrane. Studies of the sample preparation system concern factors like channel length of separators, distribution coefficients of analytes and use of a precolumn instead of loop for chromatographic injections. Effects of the internal diameter of the analytical column as well as the detection of the sulfonylureas are investigated.