Electroanalytical Determination of Cysteine Using the Electrodes Based on Ternary Silver-Copper Sulfides

Abstract

The amperometric determination of cysteine, using an electrode based on ternary silver-copper sulfide, is presented. Electrochemical characterizations (using cyclic voltammetry) of three electrode materials revealed that the electrode based on the material that consists of jalpaite (Ag3CuS2), doped with a small amount of metallic silver, has the best electrocatalytical performance for cysteine oxidation. For the amperometric determination, 0.142 V at pH 5 and 0.04 V at pH 7 vs. Ag/AgCl, related to the electrocatalytical oxidation of thiol group, were chosen. Electrochemical impedance spectroscopy together with Fourier transform infrared spectroscopy (FTIR) revealed that oxidation takes place on the electrode surface with fouling effect, which does not affect a wide linear working range between 1 μM and 100 μM. Sensitivities, at pH 5 and pH 7, are calculated to be 0.11 μA μM−1 and 0.10 μA μM−1, respectively. The detection limits were determined to be 0.036 μM and 0.024 μM for pH 5 and pH 7, respectively. In the presence of uric acid, folic acid, ascorbic acid, and glucose no interference was noticed. This electrode showed remarkable stability and excellent reproducibility. The electrode was exploited for the determination of cysteine in a dietary supplement with the excellent recoveries.

Electrochemical Amino Acid Sensing: A Review on Challenges and Achievements

“…In addition to noble metals, copper compounds, in either oxide [ 77 , 105 ], sulphide [ 106 ] or other complex forms [ 107 , 108 , 109 , 110 , 111 ] have also been interesting options for researchers in this field owing to the high affinity of copper for the sulphur moiety of cysteine. In an interesting study, Li et al [ 105 ] synthesized an octahedral Cu 2 O/polystyrene composite and, consequently, removed the styrene from the Cu 2 O lattice easily by treating the Cu 2 O/polystyrene composite with tetrahydrofuran to obtain hollow cubic Cu 2 O particles.…”

Voltammetric Electrochemical Behavior of Carbon Paste Electrode Containing Intrinsic Silver for Determination of Cysteine

“…The mediator was ternary silver-copper mixed sulfide with composition: metallic silver, Ag1.2Cu0.8S and CuAgS; composition of the mediator was determined by XRD analysis [40]. This mediator was synthesized according to the proposed method [10,40] in the presence of an excess of the metal ions. The mole ratio and molarity details of the ions in the preparation procedure are given in Table 2.…”

“…In our previous paper we focused on the investigation of the electrochemical behavior of cysteine on different crystal electrodes based on silver-copper sulfides. Electrode material comprising metallic silver and jalpaite showed the best electrochemical behavior towards cysteine [10]. A number of studies have shown that silver is a good substrate for electrodes for the selective determination of thio compounds, in the range of submicromolar concentrations, at low applied potential [11].…”

MnO2 nanorods modified screen-printed electrode for the electrochemical determination of Sudan dye in food sample

“…People associate specific colors with specific flavors, therefore, the colors of food can affect their perception of taste, especially their perception of sweets and beverages. Artificial dyes may improve on natural variations in color, may enhance colors that occur naturally, or may provide color to colorless and "fun" food, thereby making it appear more attractive and appetizing, e.g., adding a red, yellow or green color to gummy sweets, which would naturally be colorless [1,2].…”