SIMULTANEOUS DETERMINATION OF PHOSPHATE AND PYROPHOSPHATE BY AN AMPEROMETRIC FLOW-INJECTION SYSTEM WITH IMMOBILIZED ENZYME REACTORS

A bioamperometric flow-injection system is proposed for the simultaneo us determination of phosphate and pyrophosphate. The injected sample i s split so that part passes through an immobilized inorganic pyrophosp hatase reactor before passing through a coimmobilized nucleoside phosp horylase-xanthine oxidase reactor. The other portion passes only throu gh the latter reactor. Because each channel has a different residence time, two peaks are obtained. The first peak corresponds to phosphate and the second peak to the total phosphate (phosphate plus pyrophospha te). The maximum currents of both peaks are linearly related to the co ncentration of phosphate and total phosphate, respectively; 20 samples per hour can be processed with an RSD < 1.5%.