DIRECT AND SIMULTANEOUS DETERMINATION OF URIC-ACID AND GLUCOSE IN SERUM WITH ELECTROCHEMICAL FILTER/BIOSENSOR FLOW-INJECTION ANALYSIS SYSTEM

A flow-through electrolysis cell, named an electrochemical filter (ECF), with a three-electrode configuration was developed for the elimination and determination of electrochemically active components in biofluids, which give generally a nonspecific response to electrochemical biosensors. The use of a reference electrode ensured the precise control of the working electrode potential of the ECF and thus the quantitative current efficiency of the electrolysis. A flow-injection analysis setup was constructed by connecting two ECFs and a flow-through amperometric biosensor for glucose in series for the direct and simultaneous determination of glucose and uric acid in serum. The first ECF coulometrically determined uric acid, and the second one eliminated interferents with the biosensor: the sample was thus treated on-the-fly and then delivered to the biosensor, so that it determined glucose amperometrically without interference. The concentrations of glucose and uric acid measured in human control sera agreed well with the values determined with conventional methods. The system exhibited the wide dynamic range in the high glucose concentration region, thus can be applied to the analysis of serum of hyperglycaemic patients.