Continuous-Flow Assay with Immobilized Enzymes for Determining of Inorganic Phosphate in Serum

An automated method for the determination of inorganic phosphate based on flow-injection analysis and on the use of immobilized enzymes is reported. The method features a linear range between 0.1 and 20 tmol/L with a CV <2.1 % and 3.4 % for the within-run and between-run studies, respectively, and a sampling throughput of 40 h’. The sensitivity of the method makes a 1:250 dilution of the serum samples feasible, thus making undetectable the interferences from analytes commonly present in se-rum. The method shows an excellent correlation with conventional automated analyzers based on the same enzymatic reaction (Hitachi, r = 0.988) but with the cata-lyst in solution, and with the Kodak Ektachem method (r = 0.974) based on the use of dry reagents and formation of the phosphomolybdo heteropolyacid