Enzymatic method for determination of inorganic phosphate in serum and urine with a centrifugal analyzer.

We describe an enzymatic method for determining inorganic phosphate in serum and urine, with use of the “CentrifiChem.” The sample is mixed with a combined enzyme-substrate system consisting of the enzymes phosphorylase a, phosphoglucomutase, and glucose-6-phosphate dehydrogenase, the coenzyme NADP, the substrate glycogen, and adenosine 5’-monophosphate as the activator for phosphorylase. The increase in absorbance at 340 nm as NADPH is formed is linearly proportional to the concentration of inorganic phosphate to 15 mg P/dl. This method circumvents deproteinization and requires only 10 l of sample. Results obtained with the automated enzymatic method show good correlation with manual and automated molybdenum blue methods.