Browsing by Author "Pokpas, Keagan William"

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    Graphene-modified pencil graphite bismuth-film electrodes for the determination of heavy metals in water samples using anodic stripping voltammetry
    (University of the Western Cape, 2013) Pokpas, Keagan William; Jahed, N.; Iwuoha, Emmanuel
    Electrochemical platforms were developed based on pencil graphite electrodes (PGEs) modified with electrochemically deposited graphene (EG) sheets and Nafion-graphene (NG) nanocomposites in conjunction with an in situ plated bismuth-film (EG-PG-BiE and NG-PG-BiE). The EG- and NG-PG-BiEs were used as sensing platforms for determining Zn2+, Cd2+ and Pb2+ by square wave anodic stripping voltammetry (SWASV). EG sheets were deposited onto pencil graphite electrodes by cyclic voltammetric reduction from a graphene oxide (GO) solution, while a dip coating method was used to prepare the NG-PG-BiE. The GO and graphene, with flake thicknesses of 1.78 (2 sheets) and 2.10 nm (5 sheets) respectively, was characterized using FT-IR, HR-SEM, HR-TEM, AFM, XRD and Raman spectroscopy. Parameters influencing the electroanalytical response of the EG-PG-BiE and NG-PG-BiE such as, bismuth ion concentration, deposition potential, deposition time and rotation speed were investigated and optimized. The EG-PG-BiE gave well-defined, reproducible peaks with detection limits of 0.19 μg L-1, 0.09 μg L-1 and 0.12 μg L-1 for Zn2+, Cd2+ and Pb2+ respectively, at a deposition time of 120 seconds. The NG-PG-BiE showed similar detection limits of 0.167 μg L-1, 0.098 μg L-1 and 0.125 μg L-1 for Zn2+, Cd2+ and Pb2+ respectively. For real sample analysis, the enhanced voltammetric sensor proved to be suitable for the detection and quantitation of heavy metals below the US EPA prescribed drinking water standards of 5 mg L-1, 5 μg L-1 and 15 μg L-1 for Zn2+, Cd2+ and Pb2+ respectively.
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    Microfluidic graphenised-paper electroanalytical devices (μGPED) for adsorptive cathodic stripping voltammetric detection of metal contaminants
    (University of the Western Cape, 2017) Pokpas, Keagan William; Jahed, Nazeem; Iwuoha, Emmanuel I.
    The need for clean, non-toxic drinking water supplies, free of pollutants and metal contamination is vital in impoverished areas and the developing world alike. With this in mind, the development of accurate, inexpensive, portable and simple devices for remote sensing applications is therefore pivotal for early detection and the prevention of illnesses. Over the last two decades, adsorptive stripping voltammetry (AdSV) has emerged as a superior detection method over common analytical techniques due to its low-cost instrumentation, unskilled labour and ability to detect a wide range of analytes.