Patent ID: 8440422

Claim:
A method for measuring phosphoric acid in a test sample, comprising the steps of: step 1) incubating a solution comprising: a) a dehydrogenase; b) enzymes that catalyze a reaction of phosphoric acid to make a substrate for the dehydrogenase; and c) thio-NADP, thio-NAD, NADP or NAD; such that the concentration of free phosphoric acid in the solution is reduced; step 2) then adding to the solution: a) thio-NADP, thio-NAD, NADP or NAD; b) i) when component (a) of step (2) is thio-NADP or thio-NAD, component (b) is NADPH or NADH ii) when component (a) of step (2) is NADP or NAD, component (b) is thio-NADPH or thio-NADH; and c) the test sample; and step 3) determining spectrophotometrically the change in concentration of thio-NADPH, thio-NADH, NADPH or NADH, and interpreting the change as corresponding to the amount of phosphoric acid in the test sample.