Electrocatalytic detection of amitrole on the multi-walled carbon nanotube–iron (II) tetra-aminophthalocyanine platform
- Authors: Siswana, Msimelelo P , Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265924 , vital:53901 , xlink:href="https://doi.org/10.3390/s8085096"
- Description: It is shown that iron(II) tetra-aminophthalocyanine complex electropolymerized onto a multi-walled carbon nanotube-modified basal plane pyrolytic graphite electrode greatly enhanced the electrocatalytic detetion of amitrole (a toxic herbicide), resulting in a very low detection limit (0.5 nM) and excellent sensitivity of 8.80±0.44 μA/nM, compared to any known work reported so far. The electrocatalytic detection of amitrole at this electrode occurred at less positive potential (~0.3 V vs Ag|ACl) and also revealed a typical coupled chemical reaction. The mechanism for this response is proposed. The electrode gave satisfactory selectivity to amitrole in the presence of other potential interfering pesticides in aqueous solutions.
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Electrocatalysis of asulam on cobalt phthalocyanine modified multi-walled carbon nanotubes immobilized on a basal plane pyrolytic graphite electrode
- Authors: Siswana, Msimelelo P , Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6595 , http://hdl.handle.net/10962/d1004344
- Description: This work describes the electrochemical properties of cobalt tetra-aminophthalocyanine (CoTAPc) complex electropolymerized at the surface of multi-walled carbon nanotube (MWCNT) abrasively immobilized onto a basal plane pyrolytic graphite electrode (BPPGE). The constructed electrode displayed excellent electrocatalytic behaviour towards the oxidation of the herbicide, asulam, as evidenced by the enhancement of the oxidation peak current (~6 times) and the shift in the oxidation potential to lower values (by ~120 mV) in comparison with the bare BPPGE. The chronoamperometric detection of asulam which was carried out in 0.10 M phosphate buffer (pH 7.0) at a fixed potential of 0.65 V (versus Ag|AgCl) yielded excellent analytical parameters; a linear concentration range of 4.5–20 μM, a sensitivity of 241 × 10[superscript −3] μA/μM, a detection limit of 1.15 μM asulam (using the Y[subscript B] + 3σ criterion) and a response time of ~2 s.
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Electrocatalytic behaviour of carbon paste electrode modified with iron(II) phthalocyanine (FePc) nanoparticles towards the detection of amitrole
- Authors: Siswana, Msimelelo P , Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6591 , http://hdl.handle.net/10962/d1004340
- Description: This paper describes the construction of a carbon paste electrode (CPE) impregnated with nanoparticles of iron(II) phthalocyanine (nanoFePc). The new electrode (nanoFePc-CPE) revealed interesting electrocatalytic behaviour towards amitrole; pure catalytic diffusion-controlled process, with high Tafel slope (235 mV/decade) suggesting strong binding of amitrole with nanoFePc catalyst. The effects of catalyst loading, varying pH and electrolytes were studied. The mechanism for the interaction of amitrole with the nanoFePc is proposed to involve the Fe[superscript (III)]Pc/Fe[superscript (II)]Pc redox process. Using chronoamperometry (E = +0.42 V versus Ag/AgCl) technique, the sensor was reliably employed for amitrole assay at pH 12.0 phosphate buffer (with sodium sulphate as the supporting electrolyte) for up to 12 nM amitrole with excellent sensitivity (ca. 3.44 μA/nM) and low detection limit (3.62 ± 0.11 nM, i.e. 0.305 μg L[superscript (−1)] using the YB + 3σB criterion and 0.85 ± 0.03 nM, i.e. 70 ng/L with the Y[subscript B] + 2[subscript σB] criterion) as well as satisfactory amperometric selectivity coefficient (K[subscript amp] ≈ 7.4 × 10[superscript (−4)] for ammonium thiocyanate, a component of many amitrole herbicides, and 3.2 × 10[superscript (−3)] for asulam pesticide). The surface of the electrode can easily be regenerated by simple polishing on an alumina paper, obtaining a fresh surface ready for use in a new assay. The proposed electrode was successfully applied in the quantification of amitrole in its commercial formulation as well as in tap water samples.
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