Comparative study of methodologies for the analysis of PCDDs and PDCFs in powdered full-fat milk. PCB, PCDD and PCDF levels in commercial samples from Spain.

Feasibility of two different extraction methods involving solid-liquid extr action and Soxhlet extraction, previously used for the determination of lip id contents and PCB levels on powdered full-fat milk, are now examined for simultaneous PCDD/F analysis. The results of this study are consistent with those found for PCBs. The solid-liquid procedure provides the most efficie nt extraction of both labelled spiked and endogenous PCDD/Fs with the lowes t variability. The average recoveries were 101% (R.S.D. = 6.9%) for C-13(12 )-2,3,7,8-TCDD and 95% (R.S.D. = 11%) for C-13(12)-1,2,3,4,7,8-HxCDD. The R .S.D.s for endogenous 2,3,7,8-PCDD/Fs were in the 9.3-25% range. In additio n, this methodology simplified the subsequent cleanup step as it allowed a semi-selective extraction of the apolar lipids from the milk. The proposed method was applied to simultaneous PCB and PCDD/F analyses in different bra nds of powdered full-fat milks commercially available in Spain. In all case s, very similar PCB and PCDD/F levels were found. Differences among batches from the same manufacturer were even lower. The total i-TEQ average for PC DDs and PCDFs in the 22 powdered full-fat milk samples analysed was 1.87 pg /g fat basis. This value was similar to those found in cow's milk from othe r European countries. (C) 1999 Elsevier Science Ltd. All rights reserved.