ELECTROCHEMICAL INVESTIGATION OF CYSTEAMINE AT CARBON FIBER MICRODISK ELECTRODE

Abstract

The electrooxidation of cysteamine compound was carried out using convolutive cyclic voltammetry, linear sweep voltammetry and chronoamperomtry techniques at a carbon fiber microdisk electrode in 0. 1 M perchloric acid. The electrooxidation potential ( E0'' ) of cysteamine occurs at + 0.921 V. The mechanistic pathway of electrooxidation process at carbon fiber microelectrode is loss of 1 electron per molecule. The electrode process is controlled mainly by diffusion. The chemical and electrochemical parameters of the investigated system were determined experimentally and verified theoretically via digital simulation method. The unique properties of microdisk electrodes offer a number of particular advantages for their use in analytical applications. In the steady-state mass transport to the microdisk is dominated by quasi-hemispherical diffusion. As a consequence, the mass transport to and from the microdisk electrode surface is efficient, reproducible and insensitive to random convection. In analytical applications based on accumulation and stripping techniques this obviates the need for stirring during the preconcentration step, improves the precision of the measurement, and reduces analysis times. In addition, the small electrode surface area of the microdisk means that the double layer capacitance of the electrode is small, thus significantly reducing the charging current. As a consequence, the ratio of the steady-state Faradaic current to the non-Faradaic current is increased and the detection limit is enhanced.1 The small size of the electrodes also means that the currents passed at the microelectrode are small resulting in negligible ohmic drop (iR drop) even in the absence of a supporting electrolyte.2,3 This has dual advantages in analytical applications that sample preparation can be simplified and that the possibility of impurities from the added electrolyte is eliminated. Microelectrodes are thus particularly well-suited for trace analysis. Pt, Au, Hg and carbon microelectrodes have been used in stripping analyses for the determination of trace metals by a number of authors.4-8 In contrast, studies using microelectrodes for the determination of organic species are far less numerous and are restricted to the use of carbon fiber microelectrodes. 9-19