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Abstract
A supported liquid membrane system has been developed for the extraction of phenolic acids for circulating nutrient solutions for tomato culture. A porous PTFE membrane is impregnated with an organic solvent, which thus forms a barrier between two aqueous phases. The analytes are extracted from an aqueous donor solution into the hydrophobic membrane and then back extracted into a second aqueous solution, the acceptor, were the analytes are irreversible trapped. By pumping the donor and keeping the acceptor stagnant, an enrichment of analytes in the acceptor is achieved. The final determination is performed with liquid chromatography and UV-detection utilised with a PRP-1 packed precolumn replacing the injection loop. The stability of five phenolic acids (p-hydroxy benzoic acid, vanillic acid, caffeic acid, p-coumaric acid and ferulic acid) in the nutrient solutions during various storage conditions is reported. High flow rates (up to 6.5 mL/min) are for the first time reported with the SLM-technique, which gives detection limits around 1 nM after 30 minutes enrichment of a number of different phenolic acids.