Abstract: In a conventional method for the quantitative determination of substances, particularly in serum, which, by action of an oxidase thereon, combine with oxygen to form hydrogen peroxide and wherein the hydrogen peroxide formed is converted, in the presence of methanol and catalase, to formaldehyde, the formaldehyde is reacted with hydrazone in the presence of ferric chloride, and the dye thus formed is determined photometrically, the improvement comprising using as the hydrazone, 3-methyl-2-sulfonylbenzothiazolone-hydrazone; use of this hydrazone results in the formation of a very easily soluble dye and is suited for use in automatic analyzers.

Abstract: An analytical process for enzymatic determination of a substrate in biological fluids. The fluid sample is reacted first in the absence of the specific kinase but in the presence of an NADH -- regenerating enzymatic system with the reagents needed for the reaction sequence; then the enzymes are separated from the reaction solution, and thereafter the necessary enzymes are added to the filtrate and NADH consumption is measured.The method is very accurate, economical in requiring less enzymes and only one measurement is necessary.