CONDITIONS FOR THE MEASUREMENT OF TOTAL ALKALINE-PHOSPHATASE ACTIVITY IN HUMAN SERUM

While developing a standard method for measuring total alkaline phosphatase activity in human serum at 30-degrees-C, the influence of buffer (2-amino-2-methyl-1-propanol), substrate (4-nitrophenyl phosphate), pH, magnesium ion, zinc ion, complexing agent (ethylenediaminetetraacetate), volume fraction of specimen and the mode of initiation of the reaction have been studied. The final reaction conditions are: 2-amino-2-methyl-1-propanol, 0.35 mol L-1; 4-nitrophenyl phosphate, 16 mmol L-1; pH30-degrees-C 10.50 +/- 0.05; magnesium ion, 2 mmol L-1; zinc ion, 1 mmol L-1; ethylenediaminetetraacetate, 2 mmol L-1 and sample dilution 1/51. These results appear to be a good compromise between clinical requirements for precision and economy and they serve to promote flexible and practical use of the metal-ion buffer method as a routine method in clinical chemical laboratories.