Faculty of Applied Sciences
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Item 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, LukeThis 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.Item Optimisation of HPLC-based methods for the separation and detection of herbicide glyphosate and its major metabolite in water(2010) Madikizela, Lawrence Mzukisi; Moodley, Kandasamy Govindsamy; Chetty, Deenadayalan KistenWater storage dams play an important part in the collection and purification of water destined for human consumption. However, the nutrient rich silt in these dams promotes rapid growth of aquatic plants which tend to block out light and air. Glyphosate is universally used as the effective non-selective herbicide for the control of aquatic plants in rivers and dams. Invariably there is residual glyphosate present in water after spraying of dams and rivers with glyphosate herbicide. The amount of residual glyphosate is difficult to determine on account of high solubility of glyphosate in water. Thus a method of sample preparation and a sensitive HPLC method for the detection of trace amounts of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA) in water is required. A crucial step in sample preparation is pre-column derivitization of glyphosate with 9-fluorenylmethyl chloroformate (FMOC-Cl). For sample pretreatment, water samples were derivatized with FMOC-Cl at pH 9, extracted with ethyl acetate and sample clean-up was carried out by passing a sample through the SPE cartridge. For SPE, recovery studies were done to choose a suitable cartridge for glyphosate and AMPA analysis. The following cartridges were compared, namely, C18, Oasis HLB and Oasis MAX SPE cartridges. Best recoveries (101% for glyphosate and 90% for AMPA) were obtained using 500 mg of C18 solid-phase extraction cartridge. The eluent from SPE cartridge was injected into HPLC column. Three types of separation columns (namely; C18 column, silica based amino column and polymeric amino column) were compared for the separation of glyphosate and AMPA. The best separation of glyphosate and AMPA in water samples was achieved using a polymeric amino column and a mobile phase at pH 10 which contained a mixture of acetonitrile and 0.05 M phosphate buffer (pH 10) 55:45, (v/v) respectively. The method was validated by spiking tap water , deionized water and river water at a level of 100 μg/l. Recoveries were in the range of 77% -111% for both analytes. The method was also used in determining the levels of glyphosate and AMPA in environmental samples. This method gave detection limits of 3.2 μg/l and 0.23 μg/l for glyphosate and AMPA respectively. The limits of quantification obtained for this method were 10.5 μg/l and 3.2 μg/l for glyphosate and AMPA respectively.Item Detection methods of organic acid in steam/water circuits and optimisation using HPLC-UV(2009) Ramrung, Arthi; Moodley, Kandasamy Govindsamy; Chetty, Deenadayalan KistenThis study was mainly a response to a challenge faced by ESKOM in its coal-fired power stations. In spite of using high purity water to drive the turbines, the latter were damaged by ‘pitting’, possibly related to acids generated at high temperatures. In the light of this a relatively simple method for determination of short chain organic acids was identified by comparing the efficacies of several methods. It was found that high performance liquid chromatography (HPLC) method preceded by derivatization (with o-nitrophenyl hydrazine) is suitable for analyzing mixtures of simple acids at ppb levels. Calibration was effected by using methanoic acid (formic acid), ethanoic acid (acetic acid), propanoic acid (propionic acid) and butanoic acid (butyric acid). The HPLC instrument used was from Thermo Separations with P2000 pump, SN 4000 interface and UV1000 with a column heater. A comparative study between the HPLC methods using ion exclusion and partition chromatography was carried out in order to find a suitable method that can be used with aqueous environmental samples. The two essential columns that were used were ion exclusion Phenomenex Rezex OA column and a Nucleodur C8 column. The method of partition chromatography using a C8 column showed the most success using a mobile phase consisted of acidified water using HCl (pH4.5) along with a 60:40 Acetonitrile/Methanol mixture. Both isocratic and gradient programs were utilized. Limits of detection were improved from 800ppb (formic acid), 480ppb (acetic), 350ppb (propionic) and 680ppb (butyric acid) to 25ppb (acetic), 60ppb (propionic) and 90ppb (butyric). Samples used in analysis were collected from the main stream, economiser, condensers, polishing plant and turbines of the Tutuka Power Station in Mpumalanga province and analysed using with final developed methodItem Molecular characterization of aflatoxigenic and non-aflatoxigenic aspergillus isolates(2007) Mngadi, Phakamile TruthFor decades the genus Aspergillus (of fungi) has been classified based on morphological and growth criteria. Members of the Aspergillus section Flavi are economically valuable and methods of differentiating them are thus very important. Several molecular methods have been developed to distinguish these strains. Also, a number of biochemical and genetic studies have been used in order to provide a better means of classification (Lee et al., 2004). Aflatoxins, the most frequently studied mycotoxins, are produced by certain Aspergillus species/strains/isolates of fungi. The aflatoxin biosynthetic pathway studies have led to a number of discoveries. Several structural and regulatory genes (and their enzymes) involved in the biosynthesis of aflatoxins have been discovered and purified (Trail et al., 1995). Aflatoxin production and contamination of agricultural crops are major causes of economic losses in agriculture. Thus, better methods of characterization/differentiation are required for both aflatoxigenic and non-aflatoxigenic isolates. Molecular biology is one of the current tools used to differentiate between these isolates. Polymerase Chain Reaction (PCR)-based randomly amplified polymorphic DNA (RAPD) analysis has been used successfully in the analysis of DNA relatedness of species of fungi, bacteria, plants and animals. Dendograms which evaluate/assess the likeness between different isolates has also been used (Martinez et al., 2001). Restriction fragment length polymorphism (RFLP) analysis has been applied to a number of studies to detect differences between fungi and to establish relationships between them. Therefore, the scope of this study was to investigate RAPD analysis (with dendograms) and detection of RFLPs by hybridization as molecular methods that can distinctly differentiate or characterize the aflatoxigenic and non-aflatoxigenic Aspergillus isolates.