Electrochemical behaviour of dopamine at covalent modified glassy carbon electrode with l-cysteine: preliminary results

Abstract

The surface of glassy carbon (GC) electrode has been modified by oxidation of L-cysteine. The covalent modified GC electrode with L-Cysteine has been studied, according the supporting electrolyte used. Favourable interactions between the L-cysteine film and DA enhance the current response compared to that at the Nafion GC and bare GC electrodes, achieving better performances than those other electrodes. This behaviour was as result of the adsorption of the cysteine layer film, compact and uniform formation; depending on L-cysteine solution (phosphate buffer or chloridric acid supporting electrolyte) used for modifying GC surface. In cyclic voltammetric measurements, modified electrodes can successfully separate the oxidation/reduction DA peaks in different buffer solutions, but an evident dependence in the response was obtained as function of pH and modified electrode. The modified electrode prepared with L-cysteine/HCl solution was used to obtain the calibration curve and it exhibited a stable and sensitive response to DA. The results are described and discussed in the light of the existing literature.

Cysteic Acid‐Modified Glassy Carbon Electrode for Monitoring Oxalic Acid (OA) Concentration During Its Electrochemical Oxidation at Ti/Pt Anode

“…As it can be seen, the first cycle shows two anodic peaks at about 0.8 V (see Figure 1) and close to 1.7 V, and a cathodic peak at À0.55 V, similar to those reported by Wang et al [3] and Brunetti et al [6]. As previously established [3][4][5]9,10], the first peak should be attributable to oxidation of cysteine (1) to cysteic acid (7) following Scheme 1: The group SH of cysteine (1) is oxidized (4) and two molecules are absorbed at the electrode surface (5) forming cystine (6) and after oxidation, the cysteic acid is obtained (7).…”

“…In recent years, a new voltammetric method, based on the use of a glassy carbon electrode modified by electropolymerized cysteic acid, was proposed for the determination of several compounds, such as meloxicam [3], sinomenine [4], dopamine [5] and theophylline [6]. In this context, this kind of polymeric film can be considered a promising, low-cost, steady and biocompatible material for the modification of electrodes [7].…”

“…HCl containing 5.0 mmol L À1 of cysteine [5,6]. After the cysteic acid electrodeposition, the modified electrode was then rinsed with ethanol and ultrapure water to remove the physically adsorbed and no reacted species from the electrode surface.…”

“…After the cysteic acid electrodeposition, the modified electrode was then rinsed with ethanol and ultrapure water to remove the physically adsorbed and no reacted species from the electrode surface. Cys-MGC electrode was electroactivated by cyclic scanning from À0.50 V to + 0.80 V (four cycles, 50 mV s À1 ) in 0.25 mol L À1 H 2 SO 4 as supporting electrolyte [5,6].…”

Electrooxidation of DL-norvaline at Glassy Carbon Electrode: Approaching the Modified Electrode for Voltammetric Studies of Hydroquinone and Catechol

“…The biocompatibility, the low residual current over a wide range and the minimal chances to show deteriorated response [1][2][3] of GCE are some advantages of other electrodes. Several reported studies have involved electrochemical oxidation of L-cysteine, 4,5) valine, 6) glycine, 7) glutamic acid, 8) phenylalanine, 9) and L-aspartic. 10,11) Most of these studies have modified the GCE surface and therefore have been used to reduce the overvoltage, overcome the slow kinetics of many electrode processes and determination of one species as an analytical application.…”