Covalently Anchored p-Aminobenzene Sulfonate Multilayer on a Graphite Pencil Lead Electrode: A Highly Selective Electrochemical Sensor for Dopamine

An electrochemical sensor for dopamine (DA) has been developed based on the electrografting of 4-aminobenzene sulfonic acid (4-ABSA) onto the graphite pencil lead electrode (GPLE). The process of covalent anchoring and presence of 4-ABSA on the GPLE was studied using cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical behaviour of the sensor towards DA, ascorbic acid (AA), and uric acid (UA) was studied in detail in phosphate buffer of pH 7. After optimizing the various parameters that influence the differential pulse voltammetric (DPV) signal for DA, the sensor exhibited a linear response over the 0.5 - 10 molL(-1)concentration range with a limit of detection, 0.095 molL(-1) (at an S/N of 3). The sensor can selectively quantify DA even in the presence of 1 mmolL(-1) AA. Distinct DPV signals were obtained for DA (at 0.191 mV vs. Ag/AgCl) and for UA (at 0.343 mV vs. Ag/AgCl). The sensor is highly selective, sensitive and stable. It was applied to the quantification of DA in injections and urine. Recovery studies were done by spiking both the real samples with a known quantity of DA.