The authors report on the electrochemical degradation of the dye Methyl Orange (MO) on a glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes. Continuous electrochemical cycling of the modified electrode in pH 7 solution leads to reductive cleavage of the azo bond of MO to form intermediate amines such as aniline-4-sulfonic acid and 1,4-diaminobenzene. These are further converted to a highly redox-active composite consisting of quinone and polyaniline derivative respectively on MWCNT. Cyclic voltammetric experiments display two well-defined redox peaks at an equilibrium potential (E1/2) of about 0 V (A1/C1) and 0.2 V (A2/C2) vs Ag/AgCl. Physicochemical characterizations such as FT-IR and in-situ UV-vis spectroelectrochemistry support the mechanism of cleavage of MO. The composite modified electrode is shown to be a viable sensor for use in flow injection amperometric analysis of ascorbic acid (AA; vitamin C) at a potential of −0.15 V (vs Ag/AgCl). No interferences were observed with cysteine, glucose, dopamine, citric acid, nitrite, and uric acid. The measured current is linearly related to the AA concentration in the range from 1 μM to 700 μM, with a 115 nM limit of detection (at an S/N ratio of 3). The method was successfully applied to the selective quantification of AA in two pharmaceutical samples.
Microchimica Acta – Springer Journals
Published: Jun 6, 2017
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