Sensitive and Selective Determination of Dopamine at a Nanocomposite Modified Sensor

A sensitive electrochemical sensor for determination of dopamine has been developed by modification of carbon paste electrode (CPE) with graphene (GRP), chitosan (CHIT) and zirconium oxide (ZrO₂) nanoparticles. The morphological characteristics of nanocomposite (GRP-CHIT-ZrO₂) were studied by scanning electron microscope and atomic force microscopy. Electrochemical characterization of the modified sensor was done using cyclic voltammetry and electrochemical impedance spectroscopy. Enhancement in electron transfer process and reduction in charge transfer resistance was observed. Electrochemical behavior of dopamine at nanocomposite modified CPE (GRP-CHIT-ZrO₂/CPE) was investigated in pH 7.4 phosphate buffer solution using cyclic voltammetry and square wave voltammetry. The modified sensor showed enhancement in current response as compared to bare CPE. The modified sensor showed a linear response for dopamine in the range 1000 to 5000 nM. The limit of detection and limit of quantification were found to be 20 and 67 nM respectively which is lower than many other sensors reported for dopamine in literature. The modified sensor showed high sensitivity (2.23 nA/nM) and selectivity for determination of dopamine. The method was also successfully employed for determination of dopamine in human blood serum samples.