title: Proficiency testing has improved the quality of data of total vitamin B2 analysis in liquid dietary supplement.
abstract: A previously reported proficiency test for the analysis of vitamin B(2) in liquid dietary supplement demonstrated bimodality. The same trend has now been observed in four subsequent tests of this type. The trend would not so easily have been observed without applying a fit-for-purpose standard deviation that is more generous than that predicted by the Horwitz equation. Since originally reporting the bimodal problem and hypothesising its cause by incomplete enzymic digestion of riboflavin-5-phosphate, there has been a general improvement in the reporting of the higher mode. This is thought to correspond to free riboflavin following complete digestion of the sample. Several individual participants appear to have learned from the experience and have changed their reporting of the lower mode to the higher mode.
authors.affiliation: The Food and Environment Research Agency, Sand Hutton, York YO41 1LZ, UK. mark.sykes@fera.gsi.gov.uk
authors.forename: Mark
authors.initials: M
authors.lastname: Sykes
authors.forename: Joanne
authors.initials: J
authors.lastname: Croucher
authors.forename: Rosemary Ann
authors.initials: RA
authors.lastname: Smith
mesh_terms: D019587:Dietary Supplements; D011786:Quality Control; D015203:Reproducibility of Results; D012256:Riboflavin / Q000032:analysis*
chemical_list: D012256:Riboflavin