[Modification of the spectrophotometric method of determination of pyridoxal-5'-phosphate and pyridoxal in enzymatic preparations].

In quantitative measurements of pyridoxal-5'-phosphate and pyridoxal in enzymes routinely used phenylhydrasine was substituted for 4-nitrophenylhydrasine. This increased the sensitivity of the method by 70%. The modified procedure had another advantage: it allowed measurements of the optic density of resulting 4-nitrophenylhydrasones at 430 nm for acid solutions and at 550 nm for alkaline solutions.