DEVELOPMENT AND CERTIFICATION OF REFERENCE MATERIALS FOR RESIDUES OF ORGANOCHLORINE AND ORGANOPHOSPHORUS PESTICIDES IN BEEF FAT ACSL CRM-1 AND CRM-2

Beef fat samples were prepared and tested as candidate reference mater ials for organochlorine and organophosphorus pesticides. The CRMs cons isted of beef fat spiked with pesticide solutions. One sample (ACSL CR M 1) was prepared containing close to 0.2 mg/kg of each of the organoc hlorine pesticides dieldrin and heptachlor epoxide. A second sample (A CSL CRM 2) was prepared containing close to 0.8 mg/kg of each of the o rganophosphorus pesticides diazinon, chlorpyrifos and ethion. The spik ing levels and homogeneity of the materials were verified. The coeffic ients of variation of 5 analyses carried out to test between-jar homog eneity for each reference material were dieldrin, 3.5%; heptachlor epo xide, 1.1%; diazinon, 2.1%; chlorpyrifos, 1.2% and ethion, 3.1%. No in stability in any of these compounds was detected over a twelve month p eriod. The candidate reference materials were found to be suitable for certification by interlaboratory testing. The certification process w as based on a two-stage nested design described in ISO Guide 35. Analy sis of results reported by collaborating laboratories provided an asse ssment of the homogeneity of the reference materials. The certified va lues together with their upper and lower 95% confidence limits are: [G RAPHICS] A certificate for each material was prepared according to the guidelines set out in ISO Guide 31.