Simultaneous determination of hypoxanthine, inosine and inosine 5′-monophosphate with serially connected three enzyme reactors Original Research Article

A biosensor system for simultaneous determination of hypoxanthine (Hx), inosine (HxR) and inosine 5′-monophosphate (IMP) was developed to measure fish freshness indices such as Ki and H value in a convenient way. The biosensor which is composed of three enzyme reactors packed with enzyme-bonded chitosan porous beads (Chitopearl) was operated in a flow injection analysis mode with a serial circuit system. The optimum combination of column length for the Hx–HxR–IMP reactor which permitted a complete reaction between substrate and immobilized enzyme at the respective enzyme reactor was 15, 12 and 7 cm, respectively. The concentrations of Hx, HxR and IMP were determined simultaneously based on the sensor response from each enzyme reactor. The accuracy of this system was proved by a model study, and the Ki- and H-values for various fish samples were determined. The analytical results by the biosensor system did correlate well with those obtained by liquid chromatography.