Preliminary studies for fluorometric determination of pyridoxal and of its 5'-phosphate.

Bonavita (1) found that the reaction of pyridoxal (PAL) and of pyridoxal 5•Œ-phosphate (PAL-P) with cyanide in a slightly alkaline solution produced highly fluorescent compounds and this reaction has been applied to fluoro metric determination of PAL and PAL-P as "cyanohydrin method" . Recently it was found that PAL and PAL-P were oxidized with oxygen by a catalytic action of cyanide to 4pyridoxolactone (PiAL) and 4-pyridoxic acid 5•Œ-phosphate (PiA-P) respectively (2, 3). The present studies deal with some fundamental works which were carried out in order to utilize the reaction to fluorometric determination of PAL and PAL-P in biological materials. The fluorescence intensity of the reaction product obatined from PAL was found to be much stronger than that from PAL-P and PAL could be more easily separated from interfering substances than PAL-P. For de termination of PAL-P it is therfore preferable to determine it as PAL after hydrolysis. The hydrolysis of PAL-P, the reaction condition and interfering substances were studied.