DETECTION OF AROCLOR, DDT, MALATHION AND HCB USING SEMIPERMEABLE MEMBRANES AS CONCENTRATION METHOD

Semipermeable membrane devices (SPMDs) containing 1 g of triolein were used to extract pp'-DDT (DDT), hexachlorobenzene (HCB), malathion and aroclor 1254 from aqueous samples. Recoveries higher than 95% were analytically confirmed for DDT and HCB using GC-MS after an extraction with n-hexane or methylene chloride. Different approaches were made to combine this concentration method with biological detection systems using toxicity tests on Daphnia magna. Direct assays, introducing the exposed membrane into the exposure flask, gave negative results due to the adhesion of the animals to the membrane. Similar negative results were observed when triolein aliquots were directly mixed with the water in the exposure chamber. Finally, the capability of dimetylsulfoxide as solvent (DMSO) was assayed. DMSO war, chosen because of its compatibility with ecotoxicity assessments. Membranes were dialysed twice with DMSO. The toxicity of dimethylsulfoxide extracts to Daphnia magna was assessed by the standard acute toxicity test modified for low volume assays. HCB containing extracts were slightly toxic, while no toxicity was observed for DDT, malathion and aroclor 1254. Chemical analysis confirmed a very low recovery, less than 10%; aroclor was not quantified. Data show that although DMSO is a very good solvent for toxicity studies, it can not be used to extract lipophilic pollutants from triolein devices. Nevertheless, the capability of these devices to concentrate hydrophobic pollutants has been confirmed, and new efforts to combine this concentration method with toxicological detection systems are required. The possibilities of these methods are discussed.