Development of Electrospun Nanofibres for the Pre-Concentration of Organochlorines.
A Thesis Submitted to the School of Postgraduate Studies, University of Lagos.
There has been an increasing concerns on public health implication of Organochlorines contamination of the environment. Organochlorines are widely used in Pharmaceutical industries and agricultural purposes worldwide most especially as disinfectants, pesticides and industrial fluids. As a result of its acute toxicities, the compounds are attracting strict legislation by various regulatory bodies across the world. As a consequence, there is a greater need to develop and improve the existing pre-concentration methods for the analysis of these compounds. The extraction of Organochlorines is traditionally carried out to isolate the trace analytes from the complex matrices. Solid Phase extraction (SPE) has gained a wide recognition for extraction of Organochlorines due to its simplicity of operation and good reproducibility. However, the conventional sorbents in SPE have limitations of specificity for analyte. In recent times, electrospun nanofibres is sought as an alternative sorbent for pre-concentration of trace analytes. Hence, in this study, we developed and characterized electrospun polystyrene nanofibers incorporating different potassium salts of imidazole-1-carbodithioate for pre-concentration of Organochlorines. The diameter of Electrospun Polystyrene nanofibers ranged from 130-500 nm. The sorption and desorption of a model Organochlorine pesticide; pp-1,1-dichloro-2,2 bis-(4-chlorophenyl) ethylene, DDE (0.25-2.0 µg L-1) on the nanofibers were optimized and and monitored with Gas Chromatography. Optimum sorption of DDE (0.50 µg L-1) on electrospun Polystyrene and carbodithioate incorporated Polystyrene nanofibres was at 43.7% and 94.6% respectively in 20 min, while optimal desorption on the Pressurized Hot Water Extraction system was 96.5 % in 30 min. The incorporation of diazole carbodithioate (diazoles) doubled the sorption efficiency of electrospun polystyrene nanofibres and achieved a Limit of Detection of 0.234 ng L-1 for DDE. The study shows that the functionalized electrospun nanofibrers has a great potential for pre-concentration of Organochlorines and the application of PHWE provides an opportunity to eliminate organic solvents in procedures aimed at monitoring of organic pollutants in the environment. The analysis for Organochlorines in fish and water samples of Lagos lagoon revealed the accumulation trends of the contaminants. The residual concentration of Organochlorines in water and fish samples varied from Non-detectable to 0.996 µg/L and 0.01 to 8.92 mg/kg wet weight respectively. The residual concentrations of Organochlorine in 37.3% of water samples analyzed were greater than European Community allowable residue limit in drinking water, while the residue concentrations of Organochlorines (except for HCHs) in fish samples were below the codex alimentarious commission of FAO-WHO allowable residue limit.