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Faculty of Applied Sciences

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Author: search.filters.author.Chimuka, Luke

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    Experimental and theoretical study of molecular interactions between 2-vinyl pyridine and acidic pharmaceuticals used as multi-template molecules in molecularly imprinted polymer
    (Elsevier, 2016) Madikizela, Lawrence Mzukisi; Mdluli, Phumlani Selby; Chimuka, Luke
    Molecular interactions between functional monomer and template molecules are regarded as the driving force for the success of a molecularly imprinted polymer. In this study, a multi-template molecularly imprinted poly-mer (MIP) for ibuprofen, naproxen and diclofenac was synthesized in an oil bath set at 70 °C for 24 hours. 2-vinyl pyridine, ethylene glycol dimethacrylate, toluene and 1,1’-azobis-(cyclohexanecarbonitrile) were used as func-tional monomer, cross-linker, porogen and radical initiator, respectively. A non-imprinted polymer (NIP) was synthesized using a similar approach with the omission of templates. Monomer-template interactions were ex-amined using Molecular Dynamics and Fourier Transform Infrared Spectroscopy (FTIR). Both molecular dynam-ics and FT-IR results indicated the formation of the hydrogen bond between the templates and 2-vinyl pyridine. Molecular dynamics further revealed the identity of the hydrogen atoms in the templates involved in interactions with nitrogen atom on the functional monomer in the presence of toluene molecules. Surface area obtained for the MIP using Brunauer, Emmett and Teller method was 282 m2/g, whereas 232 m2/g was obtained for the NIP. This indicated that MIP has more binding sites compared to the NIP. Furthermore, batch adsorption and se-lectivity experiments were carried out in the presence of gemfibrozil as the competitor. When such experiments were carried out in toluene, the adsorption capacities (mg/g) obtained for naproxen, ibuprofen, diclofenac and gemfibrozil were 14.4, 11.0, 14.0 and 7.5, respectively. These results show that the MIP was more selective to the compounds that were used as template molecules.
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    Determination of Triclosan and Ketoprofen in river water and wastewater by solid phase extraction and high performance liquid chromatography
    (SACI, 2014-09-17) Madikizela, Lawrence Mzukisi; Muthwa, Sindisiwe Fortunate; Chimuka, Luke
    This paper describes a simple, sensitive and rapid method for the determination of triclosan and ketoprofen in wastewater influent, effluent and river water. The method involves solid phase extraction (SPE) of target compounds using Oasis HLB sorbent. Several extraction parameters such as sample pH, sample volume, SPE cartridge and SPE elution solvent were optimized. The pH of the collected samples was adjusted to 5.5, and then 100 mL of the sample was loaded into an Oasis HLB cartridge. Methanol was used to elute the retained compounds. The eluted compounds were analyzed using reversed-phase high performance liquid chromatography with photo diode array detection (HPLC-PDA). The method was validated by spiking ultra-pure water and wastewater with different concentrations of both compounds ranging from 5 µg L–1 to 1000 µg L–1. Recoveries were in the range of 73 % to 104 %, and % RSD ranged from8%to15%.The method gave good detection limits of 0.01 and 0.08 µg L–1 for triclosan and ketoprofen, respectively. Traces of both compounds were detected in all wastewater (influent and efflu-ent) samples at a range of 1.2 to 9.0 µg L–1 and in some river water samples.