Journal of Agriculture & Life Sciences

Graphite Electrodes Modified With Polysaccharides-Osmium (VI) Tmen Layer Catalyzing the Electrochemical Oxidation of Dopamine, Ascorbate, and Urate, Forming a Multi-Analyte Sensor
Najat Beden, Lo Gorton, Mojmír Trefulka, Emil Palecek

Abstract
Mannan was modified with Os(VI)N,N, N’,N’ tetramethylethylenediamine complex to form a compound denoted Man-Os(VI)tmen and was cast on graphite electrodes to make a modified electrode (PGE/Man-Os(VI)tmen) and used as mediator to catalyze the electrochemical oxidation of compounds such as: dopamine (DA), uric acid (UA) and ascorbic acid (AA). A catalytic current was exhibited for the PGE/Man-Os(VI)tmen for oxidation of DA, UA and AA when studied with differential pulse voltammetry and cyclic voltammetry and compared with the response at bare graphite electrodes. For all the three analytes a higher current response was obtained and at lower overpotentials, however, the PGE/Man-Os (VI)tmen shows a distinct catalytic for oxidation of DA, while this response was lowest than that for UA or AA. The performance of PGE/Man-Os(VI)tmen showed an excellent sensitivity towards DA 110.500 ± 0.017 μA.μM-1 in comparison with that for UA and AA, which were 39.793 ± 0.042 and 20.616 ± 0.395 μA.μM-1 respectively, with lower limit of detection (3 SD/slope) for DA, UA, and AA of 0.003, 4.0 and 9.0 μM respectively. Additionally, a hybrid film consisting of a mixture of DA and Man-Os (VI)tmen was applied on the modified PGE, producing a modified electrode (PGE/DA-Man-Os(VI)tmen) showed long-term stability. Moreover, scanning electron microscopy of both the PGE/Man-Os (VI)tmen and PGE/DA-Man- Os(VI)tmen modified electrodes pointed out a morphological structure, where both electrodes offered a porous nature..

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