Isocitrate analysis using a potentiometric biosensor with immobilized enzyme in a FIA system

A potentiometric biosensor for the analysis of isocitrate was developed by using a CO₃^2--selective electrode and enzyme immobilization in flow injection analysis (FIA). The biosensor consisted of a peristaltic pump, injector, enzyme reactor, reference electrode, working electrode, pH/mV meter and record. The experimental parameters that influenced the sensitivity and selectivity of the biosensors were optimized in the FIA system. A linear correlation between the potential difference and logarithmic isocitrate concentration was obtained in the range of 10^-3-10^-1 M isocitrate under optimal conditions. The interference effect of major sugars and organic acids on the sensor system was less than 5%. Isocitrate concentrations of some fruit juices analyzed by the isocitrate sensor system were compared with those analyzed by gas chromatography (GC). There was no significant difference between the two analytical methods in any of the fruit juices. This suggests that the isocitrate sensor system is reliable in determining the isocitrate concentrations of foods.