Browsing by Author "Pokpas, Keagan"

Now showing 1 - 6 of 6
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    Complexation-based detection of nickel(ii) at a graphene-chelate probe in the presence of cobalt and zinc by adsorptive stripping voltammetry
    (MDPI, 2017) Pokpas, Keagan; Jahed, Nazeem; Baker, Priscilla G.
    The adsorptive stripping voltammetric detection of nickel and cobalt in water samples at metal film electrodes has been extensively studied. In this work, a novel, environmentally friendly, metal-free electrochemical probe was constructed for the ultra-trace determination of Ni2+ in water samples by Adsorptive Cathodic Stripping Voltammetry (AdCSV). The electrochemical platform is based on the adsorptive accumulation of Ni2+ ions directly onto a glassy carbon electrode (GCE) modified with dimethylglyoxime (DMG) as chelating agent and a Nafion-graphene (NGr) nanocomposite to enhance electrode sensitivity. The nafion-graphene dimethylglyoxime modified glassy carbon electrode (NGr-DMG-GCE) shows superior detection capabilities as a result of the improved surface-area-to-volume ratio and enhanced electron transfer kinetics following the incorporation of single layer graphene, while limiting the toxic effects of the sensor by removal of the more common mercury, bismuth and lead films.
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    Determination of heavy metals at the electrochemically reduced graphene oxide mercury film electrode (ERGO-HgF-PGE) using adsorptive stripping voltammetry
    (University of Western Cape, 2020) Sanga, Nelia Abraham; Jahed, Nazeem; Iwuoha, Emmanuel. I.; Pokpas, Keagan
    This work reports the use of a pencil graphite electrode (PGE) as inexpensive and sensitive electrochemical sensing platform fabricated by using electrochemically reduced graphene oxide (ERGO) in conjunction with an in-situ plated thin mercury film. For the first time the ERGOHgF-PGE sensor is proposed for simultaneous detection of cadmium (Cd2+), copper (Cu2+), lead (Pb2+) and zinc (Zn2+) using N-Nitroso-N-phenylhydroxylamine (cupferron) as complexing agent by square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV). The technique is based on the adsorption of cupferron- metal ion complexes onto the surface of the ERGO-HgFPGE at 0.1 V for 60 s carried out in 0.1 M acetate buffer solution (pH 4.6). The synthesized graphene oxide (GO) and graphene nanosheets (GNs) were characterized using different analytical techniques such as FT-IR which confirms the presence of oxygen moieties embedded in the graphitic structure and further demonstrated by UV-Vis, validating the synthesis of GO
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    Electroanalysis of sars-cov-2 specific igg and igm antibodies at microfluidic paper-based devices
    (University of the Western Cape, 2022) Du Plooy, Jarid; Pokpas, Keagan
    The Covid-19 pandemic has taken the world by storm. The infectious disease, SARS-CoV-2, was caused by a newly found virus of the corona family. With over 6 million deaths worldwide, it is evident that the SARS-CoV-2 virus is deadly. This has placed world-wide health sectors under strain, working tirelessly toward effective vaccinations, treatments and monitoring. Further research into development of more rapid, low-cost, sensitive and reliable point-of-care (POC) SARS-CoV-2 devices is required to meet the needs of developing regions and tailor vaccine antibody production to prevent further spread of the disease. Moreover, carbon-based nanostructured materials have shown to improve biosensor detection capabilities with increased electron-transfer kinetics and active surface area resulting in more effective immobilizations of antibody/antigen onto modified electrodes surface.
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    Electrochemically reduced graphene oxide pencil-graphite in situ plated bismuth-film electrode for the determination of trace metals by anodic stripping voltammetry
    (ESG, 2014) Pokpas, Keagan; Zbeda, Salma; Jahed, Nazeem; Mohamed, Nuralli; Baker, Priscilla; Iwuoha, Emmanuel I.
    An electrochemical platform was developed based on a pencil-graphite electrode (PGE) modified with electrochemically reduced graphene oxide (ERGO) sheets and in conjunction with an in situ plated bismuth-film (ERGO-PG-BiE). The ERGO-PG-BiE was used as a sensing platform for determining Zn2+, Cd2+ and Pb2+ by square wave anodic stripping voltammetry (SWASV). ERGO sheets were deposited on to pencil-graphite electrodes by cyclic voltammetric reduction from a graphene oxide (GO) solution. The GO, with flake thicknesses varying between 1.78 to 2.10 nm (2 sheets) was characterized using FT-IR, HR-SEM, HR-TEM, AFM, XRD and Raman spectroscopy. Parameters influencing the electroanalytical response of the ERGO-PG-BiE such as, bismuth-film concentration, deposition potential, deposition time and rotation speed were investigated and optimized. The ERGO-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. 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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    Few-layer binder free graphene modified mercury film electrode for trace metal analysis by square wave anodic stripping voltammetry
    (ESG, 2013) Zbeda, Salma; Pokpas, Keagan; Titinchi, Salam J.J.; Jahed, Nazeem; Baker, Priscilla; Iwuoha, Emmanuel I.;
    A binding agent free graphene modified glassy carbon electrode in combination with an in situ plated mercury film electrode (Gr-GC-HgFE) was used as a highly sensitive electrochemical platform for the determination of Zn2+, Cd2+ and Pb2+ in 0.1 M acetate buffer (pH 4.6) by square-wave anodic stripping voltammetry (SWASV). Instrumental parameters such as deposition potential, deposition time and electrode rotation speed were optimized. The Gr-GC-HgFE sensing platform exhibited improved sensitivity for metal ion detection, in addition to well defined, reproducible and sharp stripping signals. Two linear calibration curves ranging from 0 –10 μg L−1 and 0 – 60 μg L−1 were identified yielding detection limits of 0.08 μg L−1, 0.05 μg L−1 and 0.14 μg L−1 for Zn2+, Cd2+ and Pb2+, respectively, for simultaneous analysis and 0.04 μg L−1, 0.11 μg L−1 and 0.14 μg L−1 for Zn2+, Cd2+ and Pb2+, respectively, for individual analysis when using a deposition time of 120 s. For practical applications recovery studies using tap water samples spiked with target metal ions gave recoveries within 10% of the spiked amount. Much better recoveries were obtained for the individual analysis in comparison with simultaneous analysis.
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    Nickel contamination analysis at cost-effective silver printed paper-based electrodes based on carbon black dimethylglyoxime ink as electrode modifier
    (International Association of Physical Chemists, 2022) Pokpas, Keagan; Jahed, Nazeem; Bezuidenhout, Petrone
    Electrochemical detection of metal cations at paper-based sensors has been suggested as an attractive alternative to current spectroscopic and chromatographic detection techniques due to the ease of fabrication, disposable nature, and low cost. Herein, a novel carbon black (CB), dimethylglyoxime (DMG) ink is designed as an electrode modifier in conjunction with 3-electrode inkjet-printed paper substrates for use in the adsorptive stripping voltammetric electroanalysis of nickel cations in water samples. Thedeveloped method provides a novel, low-cost, rapid, and portable adsorptive stripping detection approach towards metal analysis in the absence of the commonly used toxic metallic films. The study demonstrated a novel approach to nickel detection at paper-based sensors and builds on previous work in the field of paper-based metal analysis by limiting the use of toxic metal films.