Influence of extraction on the determination of vitamin B-6 in food by HPLC

The effect of the extraction procedure on the total vitamin B-6 content in different food matrices is presented. The use of hydrochloric acid, sulphuric acid and trichloroacetic acid, combined with enzymatic hydrolysis using several commercial enzyme preparations, was tested. The results of two liquid chromatographic methods (isocratic and gradient elution) and those of microbiological assay were compared. Reproducible results were achieved using a mineral acid followed by beta-glucosidase/acid phosphatase hydrolysis for extraction of the same sample and only a few unknown compounds caused interference in the reversed-phase chromatogram However, the conversion efficiency of the enzyme preparation should always be checked. The liquid chromatographic method indicated that there was a higher vitamin content compared with the microbiological assay. This is probably due to a lower growth response of Saccharomyces with pyridoxamine and pyridoxal rather than pyridoxine.