ISO 4133:1979

The method consists in extracting of the compound with ice-cold perchloric acid solution, centrifuging, decanting and filtrating, followed by hydrolysis of the compound in a portion of the filtrate with potassium hydroxide into gluconate. Transformation of the gluconate in the extract by the following reactions: 1) with adenosine-5-triphosphate (ATP) and 2) with concomitant reduction of an equivalent amount of nicotinamide adenine dinucleotide phosphate (NADP). Photometric measurement of the amount of nicotinamide adenine dinucleotide phosphate (reduced) (NADPH) formed.