http://hdl.handle.net/11189/5517 Sun, 16 Aug 2026 08:30:32 GMT 2026-08-16T08:30:32Z https://digitalknowledge.cput.ac.za:443/retrieve/25061/ http://hdl.handle.net/11189/5517 http://hdl.handle.net/11189/5527 Title: Levels of selected alkylphenol ethoxylates (APEs) in water and sediment samples from the Jukskei River catchment area in Gauteng, South Africa. Authors: Sibali, Linda Lunga; Okwonkwo, JO; McCrindle, RI Abstract: There has been a continual search to develop sensitive analytical methods for detecting and determining organic compounds such as alkylphenol ethoxylates (APEs) in environmental samples, since they occur at very low concentration levels. Studies conducted so far in some South African waters have offered little or no information on APEs. The presence of these compounds in environmental samples is not desirable and therefore, needs to be monitored. Water and sediment samples were collected from different sites in the Jukskei River catchment area in the 2005 summer and winter seasons. Liquid-liquid extraction (LLE) and Soxhlet extraction (SE) methods (using 1:1 dichloromethane and methanol as extracting solvents) were optimised, evaluated and used to determine APEs of interest in water (unfiltered and filtered) and sediment samples, respectively. Mean percentage recoveries obtained for APEs in spiked double-distilled water were between 83.1±1.0 (OPnEOS3) and 108.1±3.5 (OP) and for sediments the range was between 96.6±0.9 (OPnEOS1) and 117.1±0.6 (OPnEOS3). The concentration levels of APEs studied in unfiltered environmental water samples were in the range of 0.25(0.03) ng/mℓ (NP) to 92.7(1.11) ng/mℓ (OPnEOS3) and 0.31(0.02) ng/mℓ (NP) to 60.1(0.51) ng/mℓ (OPnEOS3) for filtered environmental water samples. Concentration levels obtained in sediments were from 1.94(0.14) ng/gdw to 941(0.50) ng/gdw (OPnEOS3). Analytes adsorbed on the sample bottle gave concentration levels which ranged from 0.02(0.02) ng/mℓ to 0.42(0.02) ng/mℓ for APEs. All the compounds studied were found at levels higher than the European Union (EU) set levels for the protection of the aquatic environment. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/11189/5527 2010-01-01T00:00:00Z http://hdl.handle.net/11189/5526 Title: Optimization and simultaneous determination of alkyl phenol ethoxylates and brominated flame retardants in water after SPE and heptafluorobutyric anhydride derivatization followed by GC/MS Authors: Chokwe, Tlou. B; Okonkwo, Jonathan. O; Sibali, Linda. L; Ncube, Esper Jacobeth Abstract: A gas chromatography–mass spectrometry (GC–MS) method was investigated for the simultaneous analysis of two types of endocrine disrupting compounds (EDCs), i.e., alkylphenol ethoxylates and brominated flame retardants (BFRs), by extraction and derivatization followed by GC–MS. Different solid phase extraction (SPE) cartridges (Cleanert PestiCarb, C18, Cleanert-SAX and Florosil), solvents (toluene, tetrahydrofuran, acetone, acetonitrile and ethyl acetate) and bases (NaHCO3, triethylamine and pyridine) were tested and the best chromatographic analysis was achieved by extraction with Strata-X (33 μm, Reverse Phase) cartridge and derivatization with heptafluorobutyric anhydride at 55 °C under Na2CO3 base in hexane. It was observed that APE together with lower substituted PBBs (PBB1, PBB10, PBB18 and PBB49), HBCD and TBBPA can be determined simultaneously under the same GC conditions. This simple and reliable analytical method was applied to determining trace amounts of these compounds from wastewater treatment plant samples. The recoveries of the target compounds from simulated water were above 60 %. The limit of detection ranged from 0.01 to 0.15 μg L−1 and the limit of quantification ranged from 0.05 to 0.66 μg L−1. There were no appreciable differences between filtered and unfiltered wastewater samples from Leeuwkil treatment plant although concentration of target analytes in filtered influent was slightly lower than the concentration of target analytes in unfiltered influent water. The concentrations of the target compounds from the wastewater treatment were determined from LOQ upwards. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/11189/5526 2012-01-01T00:00:00Z http://hdl.handle.net/11189/5525 Title: Determination of selected phthalate esters compounds in water and sediments by capillary gas chromatography and flame ionization detector Authors: Sibali, LL; Okonkwo, JO; McCrindle, RI Abstract: The presence of phthalate esters (PAEs) in the environment is not desirable and therefore, needs to be monitored. This study reports the first data on the concentration levels of PAEs in water and sediments of the Jukskei River catchment area, South Africa. The study was conducted during the summer and winter seasons of 2005. Liquid-liquid extraction (LLE) and Soxhlet extraction (SE) methods were optimized, evaluated and used to determine PAEs of interest in water (unfiltered and filtered) and sediments samples, respectively. Mean percentage recoveries in spiked doubly distilled water ranged from 100 ± 5.32 dimethyl phthalate (DMP) – 122 ± 0.46 di-2-ethylhexyl phthalate (DEHP) and 91.6 ± 1.93 diethyl phthalate (DEP) – 117 ± 4.80 dibutyl phthalate (DBP) in sediments. The concentration levels of PAEs studied in unfiltered environmental water samples were in the range of 0.04(± 0.00) (DMP) − 9.76(± 00.1) ng mL−1(DEHP) for PAEs and from 0.09 (± 0.01) (DMP) – 4.38 (± 0.06) ng mL−1(DEHP) for filtered environmental water samples. Concentration levels obtained in sediments were from 0.05 (0.00) (DMP) – 4910 (0.36) ng/gdw (DEHP). PAEs adsorbed on the sample bottle gave concentration levels of up to 0.10 (± 0.03) ng mL−1for some samples and no analyte was detected (ND) in some cases Generally, concentrations obtained were below the water quality guideline values of United States Environmental Protection Agency (USEPA). Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/11189/5525 2013-01-01T00:00:00Z http://hdl.handle.net/11189/5524 Title: Determination of selected organochlorine pesticide (OCP) compounds from the Jukskei River catchment area in Gauteng, South Africa. Authors: Sibali, LL; Okwonkwo, JO; McCrindle, RI Abstract: Organochlorine pesticides (OCPs) are continually detected in the environment due to their increasing applications in agriculture and industry. The presence of OCPs in the environment is not desirable since they are well known to have negative impact in humans, animals and birds. Thus, there has been a continual demand to monitor the presence of OCPs within the environment. Liquid-liquid extraction (LLE) and Soxhlet extraction (SE) methods (using dichloromethane as the extracting solvent,) were optimised and evaluated for the determination of these compounds in surface water (unfiltered and filtered) and sediment samples. The crude extracts obtained were subjected to column chromatography for clean-up. Thereafter, 1 µℓ of the cleaned extracts were injected into the GC equipped with ECD. Percentage recoveries obtained for OCPs ranged from 98.90±7.32 (2,4'-DDE) - 124.1±8.23 endosulfan II (ENDO II) % and from 98.99±5.30 (2,4'-DDE) - 121.1±0.38 (4,4'-DDE) % in spiked triply distilled water and sediment samples respectively. The levels of OCPs obtained in unfiltered environmental water samples ranged from 0.631±0.03 (γ-HCH) - 1 540±0.19 ng·mℓ-1 (4,4'-DDT) while levels in filtered water samples ranged from 0.895±0.01 (γ-HCH) - 9 089±0.08 ng·mℓ-1 (HEPTA). Levels of analysed OCPs obtained in sediments ranged from 0.266±0.01 (δ-HCH) - 22 914±2.85 ng·gdw-1 (2,4'-DDE). Analytes adsorbed on the sample bottles used for water samples collection gave levels which ranged from 0.01±0.01 - 1.06±0.02 ng·mℓ-1 for OCPs. The levels obtained from the catchment were significantly higher than the water criteria values recommended by USEPA and DWAF for the protection of the aquatic environment. Levels obtained were also higher than those of other studies conducted so far in South African aquatic environments. There is, therefore, a definite pollution of the Jukskei River catchment by the OCPs studied. Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/11189/5524 2008-01-01T00:00:00Z