Abstract:The organochlorine pesticide (OCPs) residues were measured in three species of fish Tilapia zilli (Red belly Tilapia), Ethmalosa fimbriata (Bonga Shad) and Chrysichthys nigrodigitatus (Catfish). These fish species are a significant part of the diet of residents of Lagos Nigeria. The organochlorine pesticides analyzed include DDT(pp'1,1,1-trichloro-2,2-bis-(4-chlorophenyl) ethane), DDD, DDE (pp 1,1-dichloro-2, 2-bis-(4-chlorophenyl) ethylene, HCH (gamma 1,2,3,4,5,6-hexachlorocylohexane, HCB (hexachlorobenzene), Dieldrin (1,2,3,4,10,4,4a,5,6,7,8,4,5,8 dimethanonaphthalene) and transnonachlor. The analysis was done using Gas Chromatograph with Electron Capture Detector. The mean concentration of OCPs ranged from 0.01-8.92 ppm. The concentration of the OCPs (except for HCHs) in fish samples in this study were below the extraneous residue limit of 5 ppm, set by the codex alimentarious commission of FAO-WHO-1997. However, the concentrations were higher than those detected during previous studies of fish samples from Lake Victoria, Uganda in Africa. Also the levels were quite high when compared with the allowable Federal Environmental Protection Agency (FEPA), now Federal Ministry of Environment limit and can be harmful if the trend is not checked. The study also showed that concentration of OCPs were higher in adult, than in Juvenile of most of the fish and there was no correlation observed between fat content and total concentration of OCPs.

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Electrospun polystyrene (PS) nanofibers (130-500 nm) incorporating a potassium salt of imidazole-1-carbodithioate were evaluated as potential sorbents for the pre-concentration of a model organochlorine pesticide; 1,1-dichloro-2,2bis-(4-chlorophenyl)ethylene (DDE). The efficiencies of DDE (0.25-1.0 lg L -1 ) adsorption by the nanofiber sorbent followed by desorption employing pressurized hot water extraction (PHWE) were investigated and monitored using gas chromatography with electron capture detection (GC-ECD). Parameters such as time, temperature and pressure of extraction, sample volume, DDE concentration and sorbent mass were optimized. The maximum adsorption of DDE (0.50 lg L -1 ) on electrospun PS and carbodithioate incorporated PS nanofibers was at 43.7 and 94.6%, respectively, in 20 min. Incorporation of carbodithiote doubled the adsorption efficiency of PS and achieved LOD of 0.000234 lg L -1 for DDE. The optimal DDE desorption on the PHWE system was 93.8% in 10 min. It would seem that the use of electrospun nanofibers as sorbent material with subsequent desorption by PHWE has great potential and thus warrants further investigations. This approach as it uses water as an extraction solvent for an organochlorine pesticide provides an opportunity to eliminate organic solvents, especially for procedures aimed at monitoring organic pollutants in the environment.

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