T. Yao et T. Wasa, SIMULTANEOUS DETERMINATION OF PHOSPHATE AND PYROPHOSPHATE BY AN AMPEROMETRIC FLOW-INJECTION SYSTEM WITH IMMOBILIZED ENZYME REACTORS, Electroanalysis, 5(9-10), 1993, pp. 887-890
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%.