A kinetic study on the influence of the parameters in the determination of inorganic phosphate by the molybdenum blue reaction.

Parameters which influence the initial rate of formation of phosphomolybdenum blue from phosphate, molybdate, polyvinylpyrrolidone and o-phenylenediamine were investigated. From kinetic data it is concluded that polyvinylpyrrolidone not only acts as a protective colloid, but that it takes part in the reaction and a reaction mechanism is proposed dealing with the stoichiometry of polyvinylpyrrolidone. A rate procedure for the determination of inorganic phosphate in serum and urine, based on this study, is given. Deproteinization of samples is not necessary. The method is rapid requiring one minute for quantitative readings. Because of this short period there is hardly any hydrolysis of organic phosphate esters. As the rate of color development is determined blanks can be omitted. Turbid samples may be analysed with little error.