Abstract
The Co3O4/CuO composite nanopowder (NP) modified carbon paste electrode (MCPE) was prepared and immobilised by sodium dodecyl sulphate (SDS). The electrochemical performance of dopamine (DA) in 0.2 M phosphate buffer solution (PBS) of pH 7.4 at Co3O4/CuO NP MCPE immobilised with SDS (Co3O4/CuO/SDS MCPE) was investigated by cyclic voltammetric technique as well as compared with bare carbon paste electrode (BCPE) and SDS immobilised bare CPE (CPE/SDS). In addition the electrochemical responses of ascorbic acid (AA) and uric acid (UA) were tested separately and simultaneously. The effect of concentration, quantity and immobilisation time of SDS on the Co3O4/CuO NP MCPE for the detection of dopamine was examined and optimum condition was attained for further electrochemical studies. The effect of pH on the oxidation of DA at Co3O4/CuO/SDS MCPE was studied by using different pH of PBS. The obtained slope 0.0498 V/pH from the graph of pH vs. anodic peak potential shows the equal number of protons and electrons are involved in the electrochemical reaction. From the effect of scan rate studies, the slope obtained from the graph of log scan rate (ν) vs. the log of anodic peak current (Ipa) shows the adsorption controlled electrode process. The heterogeneous rate constant increases as increase in the scan rate. In the study of DA concentration variation, the limit of detection (LOD) was found to be 0.6 µM and was contrast with other reported modified electrodes, as well as revealed lower LOD value compare to most of other modified electrodes. In simultaneous determination of DA, AA and UA, the Co3O4/CuO/SDS MCPE shown good separation along with increase in the Ipa compared to BCPE, Co3O4/CuO NP MCPE and CPE/SDS. The Co3O4/CuO/SDS MCPE was effectively tested in DA injection as a real sample analysis and was found to be good percentage recovery values.
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