Contributions to the analysis of organic xenobiotics in fish

For the residue-analysis of fish samples, a method has been developed to separate the medium polar triazines and acetamides together with lipophilic xenobiotics (organochlorine pesticides, PCBs and octachlorostyrene) from fish tissue. The detection limits of the analytes are mostly within the ppt-range (ng/kg fillet) and vary between 40 and 1050 ng/kg fillet of fish. Their recoveries range from 75 to 108%, spiked at 1.5 g/kg. The substances are extracted with a mixture of petroleum ether/ethylacetate (2:1) using a soxhlet apparatus. Subsequently, the lipids in the sample extracts are reduced to 0.4% by gel chromatography. A 5 g silica gel clean-up separates the analytes according to their polarity. First, the lipophilic compounds elute with n-hexane/ethylacetate (91:9) and afterwards the more polar compounds with n-hexane/ethylacetate (1:1). Finally, the organic extracts are concentrated to 150–300 L and the compounds are detected and quantified by GC/MS.