Optically specific detection of D- and L-lactic acids by a flow-injection dual biosensor system with on-line microdialysis sampling

A flow-injection dual biosensor system with microdialysis sampling is proposed for the simultaneous determination of D-lactic and L-lactic acids. The dialysate from the microdialysis tube is delivered to a sample loop of the six-way autoinjector and then automatically injected into the flow-injection line with a dual enzyme electrode arranged in perpendicular to the flow direction. The dual enzyme electrode is constructed by hybridizing a poly(1,2-diaminobenzene) film into two sensing parts which respond selectively to D-lactic and L-lactic acids, respectively, without any cross-reactivity. The proposed flow-injection analysis method can be successfully applied to the simultaneous determination of D,L-lactic acids in alcoholic beverages.