Inhibition of molybdenum blue formation by ATP

Summary Molybdenum blue formation was not affected by the presence of ATP up to a concentration of 1.2 mM/l. At higher concentrations the color development was inhibited relative to ATP concentration, finally reaching complete inhibition. Auto-hydrolysis of ATP was found at a rate of 1.4%/h. An exact determination of inorganic phosphate in the presence of easily hydrolyzed phosphate esters requires the measurement of extinction at fixed time intervals and extrapolation back to time zero.Acknowledgment. This work was supported by a grant of the Deutsche Forschungsgemeinschaft.