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 B6 in various foods. The method is based on isocratic elution and it provides complete separation of the three major B6-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 β-glucosidase and by analysis of the two digests separately it was possible to distinguish between free pyridoxine and β-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 B6 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.