Determination of alkaline phosphatase‐hydrolyzable phosphorus in natural water systems by enzymatic flow injection

Abstract
We report an enzymatic flow injection method for automatic measurement of dissolved phosphatase‐hydrolyzable phosphorus. The method involves use of immobilized Escherichia coli alkaline phosphatase, which produces orthophosphate from phosphate monoesters, nucleoside polyphosphate, deoxynucleoside polyphosphate, inorganic pyrophosphate, tripolyphosphate, and some S‐phosphorothioate esters. The liberated orthophosphate is subsequently detected as phosphomolybdenum blue. Suppression of E. coli alkaline phosphatase activity is significantly reduced when the enzyme is immobilized and used in a packed‐bed reactor. This method offers a means of characterizing organic P compounds in the dissolved nutrient pool and has been successfully applied to the study of freshwaters, wastewaters, and sediment extracts. Phosphatase‐hydrolyzable P has potential use as an indicator of bioavailability of dissolved P other than orthophosphate in natural waters.

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