An international quality assurance (proficiency testing) scheme for the quantitated determination of daidzein, genistein and glycitein in infant formula

This quality assurance (proficiency testing) scheme was commissioned to enable the Food Standards Agency (FSA) to determine the quality of analytical results submitted by researchers measuring the concentrations of phytoestrogens in foods in FSA funded research projects and to demonstrate that FSA funded laboratories are producing consistent and precise results. Non-FSA funded laboratories from around the world were also invited to join in the scheme to increase the number participants. A secondary objective was to highlight the most successful methodologies used to analyse phytoestrogens. aterials of infant formula were prepared and tested by HPLC with UV detection for homogeneity to establish the concentration of three phytoestrogens, daidzein, genistein, glycitein and their glycoside, acetyl glycoside and malonyl glycoside conjugates in these test materials. Fourteen laboratories participated in the scheme. Test materials for analysis of daidzein, genistein and glycitein were issued to participants in October 2003 and January 2004. The results and methods of analysis were correlated and a report for each round of testing was produced to assess the competency of laboratories. These two rounds of testing were compared with the previous four rounds of testing which had been organised and the performances of laboratories were correlated and the validity of the methods of analysis used were assessed. rformances of most laboratories for analysis of daidzein, genistein and glycitein in infant formula test materials varied widely. Suitable methods that performed well for the analysis of daidzein and genistein in infant formula test materials involved a solvent extraction step followed by reverse phase HPLC with UV detection.