THE DETERMINATION OF INORGANIC PHOSPHATE IN THE PRESENCE OF LABILE PHOSPHATE ESTERS

Abstract

Conditions for the reduction of phosphomolybdic acid to molybdenum blue were established, under which labile phosphate esters were not readily hydrolysed. The procedure was based on the reduction of phosphomolybdate by ascorbic acid at pH 4.0. Under these conditions the rates of hydrolysis of phospho-creatine, acetyl phosphate and ribose-1-phosphate were 5 per oent. or less of the rates observed in the presence of the reagents used in the method of Fiske and Subbarow (J. Biol. Chem., 1925, 66, 375). The direct estimation of inorganic P in the presence of labile phosphate esters was thus rendered possible. The maximum amounts of various salts which could be present without affecting the colour development in the new method were determined. Both arsenate and silicate produced a colour; the maximum amount of the former which could be present was 2 mg. per cent. and of the latter 0.5 mg. per cent.-W. M. Holman.