Third EU MAT intercomparison on methods for the determination of vitamins B-1, B-2 and B-6 in food

An intercomparison study on the determination of vitamin B-1, B-2 and B-6 was performed as part of the EU MAT project involving 16 laboratories. Each laboratory was requested to analyse three different food samples (lyophilized pigʹs liver, mixed vegetables and wholemeal flour, respectively) using their ‘in-house’ method as well as an ‘optimal extraction protocol’ and using a common batch of takadiastase enzyme. High-performance liquid chromatography (both normal-phase and reversed-phase HPLC), microbiological assay and chemical methods were used. tamins B-1 and B-2 the agreement between laboratories (using their ‘in-house’ methods) was generally good (vitamin B-1: CVw < 5%, CVb = 16–28%; vitamin B-2: CVw < 8%; CVb = 12–40%, respectively, where CVw is the within laboratory coefficient of variation and CVb is the between-laboratory coefficient of variation) with no apparent differences between the ‘in-house’ and ‘optimal’ extraction protocols. For vitamin B-1 microbiological results tended to be higher (e.g. ca 20–50%) than HPLC results. Some further improvement could result from optimalization (i.e. lowering) of the sample-enzyme ratio. efficiency needs to be checked with each new batch of enzyme. tamin B-6 results were much more at variance (CVw = 6–13%, CVb = 36–63%), especially with the pigʹs liver. Some discrepancy was found between laboratories using dilute mineralic acid for extraction without enzyme treatment and those using trichloroacetic acid (TCA) and/or included takadiastase treatment. It is concluded that for vitamin B-6 further standardization and method improvement is needed in order to obtain acceptable variation between laboratories. In particular, B-6 vitamer interconversion during extraction and peak interference needs further study.