Electrocatalytic determination of cysteine on the multi-wall carbon nanotubes glassy carbon electrode using a homogenous mediator



The electrocatalytic oxidation of cysteine on multi-wall carbon nanotubes glassy carbon electrode (MWCNT-GCE) in phosphate buffer solution in pH (4.0) has been characterized using cyclic voltammetry, chronoamperometry and differential pulse voltammetry. The results showed that the catalytic current of 1,5-bis(3,4-dihydroxy phenyl)penta-1,4-dien-3-one (BPO) depended on the concentration of cysteine. Although cysteine itself showed a very poor electrochemical response at the glassy carbon electrode, the response could be greatly enhanced by using BPO as a mediator, which enabled a sensitive determination of cysteine. The kinetics parameters of this process were calculated, the apparent catalytic rate constant (k΄h) and electron transfer (a) were 867 M-1s-1 and 0.57 respectively. The differential pulse voltammetry response of the modified MWCNT-GCE was linear against the concentration of cysteine in the range 0.5 to 30 μM the limit of detection was found to be 0.17μM.