Development of a square wave voltammetric method for dopamine determination using a biosensor based on multiwall carbon nanotubes paste and crude extract of Cucurbita pepo L.

The development of an enzymatic biosensor for dopamine (DA) determination based on functionalized multiwall carbon nanotubes (MWCNTs) and horseradish peroxidase (HRP) obtained from the crude extract of zucchini (Cucurbita pepo L.) is proposed. The biosensor was developed by means of the immobilization of the enzyme by covalent bonding to carrier MWCNTs functionalized. In the presence of hydrogen peroxide, HRP catalyzes the oxidation of DA to o-dopaquinone and the reduction of o-dopaquinone, which requires a low potential difference. The influence on the response of analytical parameters of biosensor such as enzyme concentration, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) concentration, H2O2 concentration, pH and phosphate buffer solution concentration, as well as the electroanalytical technique, cyclic voltammetry, square wave voltammetry and differential pulse voltammetry were investigated. The analytical parameters obtained including the sensitivity, linearity, precision, accuracy, and stability were investigated and were within the recommended guidelines. The validated method proved to be efficient for DA determination in pharmaceutical formulation and presented good selectivity even in the presence of uric acid and ascorbic acid.