Methods of Extraction and Analysis of PCBs from Earthworms

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Abstract
Earthworms can constitute an excellent indicator of soil pollution by micropollutants and PCBs in particular. The foresteps of an analysis of this organochlorine in earthworms must be considered seriously if reliable results are to be obtained. In the first place the ecological class of earthworms (1) to be analysed must be chosen taking in account the pedological level in which they live and feed. Secondly one must be able to distinguish the earthworms' contamination from the contamination of the earth present in their intestinal tube (30% of the total weight). Separation of this earth by dissection of earthworms is criticised because of subsequent PCBs losses. Two methods of emptying the intestinal tube are suggested: the first by ingestion of filter paper and the second by consumption of pure silicon powder. Application conditions of these methods are presented. The first, easier to use, is unfortunately not convenient to all earthworm species. The second is more universal. The analysis of PCBs from earthworms and intestinal earth are realised by an acid digestion followed by n-hexan extraction, sulfuric acid and Florisil column cleanup and glass-capillary-gas-chromatography with ECD detection (split mode, methyl-phenyl-silicone SE 54). This study has shown that the earth chosen by earthworms for feeding has different PCBs concentrations than the average earth. Earthworms are also better punctual indicators of the average PCBs contamination of soil than a soil sample.

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