Stability of three forms of vitamin B6 to laboratory light conditions

Pyridoxine.HCl, pyridoxal.HCl, and pyridoxamine.2HCl solutions were exposed to several laboratory light treatments, and the resulting vitamin retentions were determined by the AOAC microbiological method. The 5 treatments compared were total darkness, regular laboratory light, low actinic glass protection, yellow incandescent light, and golden fluorescent light. All treatments were imposed for 8 and 15 hr, and with the vitamin solutions at both a low and a high pH. Regular laboratory light was the most destructive to the vitamins, with greater destruction at higher pH and longer exposure time in all cases. Pyridoxine retentions ranged from 97 (pH 4.5, 8 hr) to 66% (pH 7, 15 hr); pyridoxal from 97 (pH 4.5, 8 hr) to 55% (pH 6, 15 hr); and pyridoxamine from 81 (pH 4.5, 8 hr) to 47% (pH 8, 15 hr). Retentions in low actinic glassware or in clear glassware under yellow or golden fluorescent light were essentially com,lete, ranging from 94 to 106% over all treatments and all 3 forms. Results showed that either of the 2 subdued light conditions, yellow or golden fluorescent light, is suitable in vitamin B6 assays and that low actinic glassware is suitable for storing sample solutions.