Polymelamine modified edge plane pyrolytic graphite sensor for the electrochemical assay of serotonin

A sensitive and novel electrochemical method has been developed for the determination of an important neurotransmitter, serotonin, using a polymelamine modified edge plane pyrolytic graphite sensor (EPPGS). Melamine was used for the modification of sensor by electropolymerizing it at the surface of EPPGS in acidic medium to form a layer of conducting polymer. Field emission scanning electron microscopy (FE-SEM) and electrochemical impedance spectroscopy (EIS) were used for the characterization of the surface of polymer modified sensor. The electrochemical measurements were carried out using square wave voltammetry and cyclic voltammetry. The polymelamine modified sensor exhibited excellent electrocatalytic activity towards the electrochemical oxidation of serotonin, exhibiting a larger peak current and shift of peak potential to less positive potentials as compared to the unmodified sensor. The dynamic range for the serotonin determination was found between 1-100 µm and 0.1-100 µm with detection limit of 492 nM and 30 nM for unmodified and polymer modified sensors, respectively. The determination of serotonin in human blood serum and urine has been carried out. The common metabolites such as ascorbic acid, dopamine, xanthine and hypoxanthine do not interfere in the determination up to 10-fold concentration, revealing good selectivity of the proposed sensor.