Experiences in human milk analysis for halogenated hydrocarbon residues.

Factors affecting the different stages of human milk analysis for halogenated hydrocarbon residues are explored. The variation in milk fat during breast feeding and its consequences for sampling are outlined. Extraction efficiency is discussed in terms of fat content, residue recovery and sample size. The importance of clean-up procedures is illustrated by the removal of fat from the extract and unknown contaminants from adsorbents. Polychlorinated biphenyls (PCBs) are partially separated from other halogenated hydrocarbon residues on a Florisil-silicic acid column. Both packed and capillary gas chromatographic columns can be used for identification and quantification of residues in human milk. Confirmation by chemical derivation and mass spectrometry is illustrated by the perchlorination of PCBs and PCB isomer distribution respectively. Fortification of samples and the use of a collaborative study are described as a means for method evaluation.