Oxidation and detection of L-cysteine using a modified Au/Nafion/glass carbon electrode

Abstract

In this work, the electrochemical oxidation of L-cysteine (CySH) was investigated on a composite film modified electrode with Au nanoparticles dispersed in the fluorocarbon polymer (Nafion). The excellent electrocatalytic effect on CySH oxidation was attributed to the role of Au nanoparticles. The voltammetric studies revealed two anodic peaks for the oxidation of CySH in the pH range of 2.0-8.0. The electrode was used to detect cysteine at pH 2.0 and pH 7.0. At pH 2.0, a determination range of 3.0-50.0 mol/L was obtained with the detection sensitivity of 22.7 A/(mmol L 1 ), while at pH 7.0, a determination range of 2.0-80.0 mol/L was obtained with the detection sensitivity of 4.08 A/(mmol L 1 ). The detection limits were estimated to be as low as 1.0 mol/L at both pH 7.0 and pH 2.0. Additionally, at pH 7.0, the interferences of ascorbic acid and uric acid were reduced for the detection of cysteine. These made the Au/Nafion/GC electrode a promising candidate for efficient electrochemical sensors for the detection of CySH.

Electrochemical Amino Acid Sensing: A Review on Challenges and Achievements

“…Therefore, to achieve the desired sensitivity to detect cysteine in these low concentration ranges, diverse modifiers have been proposed to be exploited in electrochemical cysteine sensors. Noble metals, e.g., gold [ 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 ], palladium [ 67 ], platinum [ 67 ], silver [ 68 , 69 , 70 ], noble metal composites, e.g., gold/copper [ 71 ], gold/silver [ 72 ], gold/nickel [ 73 ], gold/platinum [ 74 ] and silver/palladium [ 75 ], have been extensively used. Additionally, metal oxides, e.g., CeO 2 [ 76 ], Cu (X) O [ 77 ], Fe 2 O 3 [ 78 ], MgO [ 79 ], MnO 2 [ 80 ], NiO [ 81 ], SnO 2 [ 82 ], TiO 2 [ 83 ], WO 3 [ 84 ], Y 2 O 3 [ 85 ] and ZnO [ 86 ], as well as organic modifiers [ 87 , 88 , 89 , 90 , …”

“… ( A ) Cyclic voltammograms of 0.5 mmol/L (a, c and d) and 0.2 mmol/L (b) cysteine at an Au/Nafion/GCE (a, b), Nafion/GCE (c) and bare GCE (d), Scan rate: 20 mV/s in PBS (pH 2.0) [ 65 ]. ( B ) Amperometric response curves of the CeO 2 NFs and Au/CeO 2 NFs modified SPCEs in 0.01 M PBS (pH 7.4) in the concentration range of 2.0–200 μM (applied potential 0.7 V) [ 102 ].…”

“…Wang et al [ 65 ] investigated the effect of Au NPs on cysteine electroanalysis, Figure 5 A, and no detectable peak was observed for cysteine at bare GCE and Nafion/GCE ( Figure 5 A, d and c). However, after adding gold NPs to the electrode, an oxidation peak emerged whose peak current increased upon increasing cysteine concentration ( Figure 5 A, b and a).…”

Electrochemical Oxidation of Cysteine at a Film Gold Modified Carbon Fiber Microelectrode Its Application in a Flow—Through Voltammetric Sensor

“…Many electrochemical strategies have been reported including chemically modified graphite electrodes [ 2 , 5 – 7 ] such as with cobalt (II) cyclohexylbutyate, praseodymium hexacyanoferrate, and Co(II)-Y zeolite modified graphite electrode; and using Nile blue A as a mediator at a glassy carbon electrode for determination of l -cysteine; Hg thin film sensor [ 8 ], biosensors based on electrodes modified with enzymes such as tyrosinase, laccase, l -cysteine desulfhydrase [ 9 – 11 ]. On the basis of the presence of the sulphuryl (-SH) function group in the structure of cysteine, its voltammetric adsorption and desorption has been investigated at a bare gold electrode [ 12 , 13 ] and composite film modified electrode with Au nanoparticles dispersed in Nafion [ 14 ]. Pulsed electrochemical detection (PED) is based on the application of repetitive multistep potential-time ( E - t ) waveforms to a noble metal electrode that manage the sequential processes of amperometric detection combined with pulsed potential cleaning.…”

Transition metal doped Sb@SnO2 nanoparticles for photochemical and electrochemical oxidation of cysteine

“…Three small features between 490 and 497 eV and two small features between 498 and 502 eV were observed in the spectra at the Sn M 4,5 -edges, which indicated the transition from the Sn 4+ 3 d state to the unoccupied p state. The features between 490 and 497 eV, and those between 498 and 502 eV, derived from Sn M 5 (3 d 5/2 and 3 d 3/2 ), respectively 30 , 31 . The Sn M -edge measurements of all four TM-SnO 2 were very similar.…”