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Soxhlet extraction with hexane + acetone (1 + 1 by volume) was used for the extraction of organochlorine pesticide residues from river sediments, followed by Florisil column chromatography clean‐up and determination by gas chromatography with an electron‐capture detector. Average recoveries exceeding 90 % were obtained using this technique. Organochlorine pesticide residue levels in sediment samples from two major rivers flowing through predominantly rice‐growing areas were determined by this method. Relatively high residue levels of organochlorine pesticides such as HCH, heptachlor and endosulfan were found in the sediments.

The use of organochlorine pesticides has caused concern due to their effects on human health and the Malaysian aquatic ecosystem, particularly so in view of their persistent and bioaccumulative properties. Since the extent of organochlorine pesticide pollution in Malaysian waterways is unknown except for isolated instances, a systematic survey has now been carried out. Water samples from various rivers were extracted, cleaned up with Florisil and analysed for the individual organochlorine pesticides by gas chromatography (GC) with an electron capture detector (ECD). DDE, DDT and heptachlor were present in all the river water samples of the west coast of Peninsular Malaysia. Other organochlorine pesticides were also identified from the water samples. However, the levels of all these are still below criteria values for Malaysian aquatic life, indicating that organochlorine pesticide pollution is less of a problem than other organic or inorganic pollutants.

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