Determination of total vitamin B6 in foods by isocratic HPLC:: a comparison with microbiological analysis

This paper describes a rapid and sensitive, high performance liquid chromatography (HPLC) method for analysis of vitamin B-6 in various foods. The method is based on isocratic elution and it provides complete separation of the three major B-6-Vitamers: pyridoxine, pyridoxal and pyridoxamine within 12 min. Samples of vegetable origin were extracted with mild acid hydrolysis prior to enzymatic digestion with acid phosphatase and beta-glucosidase and by analysis of the two digests separately it was possible to distinguish between free pyridoxine and beta-glucosylic forms of pyridoxine. Results for several food samples analysed by this method were compared to the results of a microbiological analytical method using Saccharomyces uvarum. The comparison showed a systematic difference in results obtained with the two methods. Vitamin B-6 data from the HPLC method were approximately 70% higher for animal foodstuffs, 20% higher for fruit and vegetables, but approximately 20% lower for grain products than for the microbiological method. Models explaining these differences are discussed. (C) 2003 Elsevier Science Ltd. All rights reserved.