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 (?) 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 ?m the limit of detection was found to be 0.17?m.