Results of a quality control study of different analytical methods for determination of PCDD/PCDF in egg samples

A quality control study was performed to evaluate the results of four laboratories for determination of PCDD/PCDF in egg samples. These laboratories applied four different extraction and clean-up methods, used different GC/MS-equipment and different standard solutions. Two kinds of homogenized whole egg samples had to be analyzed: egg samples from the market which showed a background contamination and egg samples from chicken raised in an area with elevated PCDD/PCDF-contamination. The results are in a good agreement. Slightly different results for individual congeners were of minor importance. With respect to administrative actions and maximum residue levels as guide lines for condemnnation, the I-TEQ-value is the most important parameter. At both contamination levels, this decisive parameter (pg I-TEQ/g fat) was determined in good agreement between all participating laboratories. Thus, the laboratory's individual method can be used.