Electropolymerization of bromothymol blue on carbon paste electrode bulk modified with oxidized multiwall carbon nanotubes and its application in amperometric sensing of epinephrine in pharmaceutical and biological samples

Abstract

A composite electrode for an amperometric detection of epinephrine (EP) has been developed by electropolymerizing bromothymol blue (BTB) on carbon paste electrode (CPE) bulk modified with multi-walled carbon nanotubes (MWCNTs). The field-emission scanning electron microscopy and the energy dispersive X-ray analysis (EDX) confirm the formation of poly(bromothymol blue). A possible mechanism of electropolymerization of BTB has been proposed. The electropolymerization of BTB on the surface of CPE involves much less energy as compared to that of glassy carbon surface. The modification enhanced the current sensitivity of EP by 5.5 times as compared to the bare CPE. The electrochemical impedance spectroscopy (EIS) studies revealed a least charge transfer resistance (Rct) for the modified electrode. The sensor showed an optimum current response at physiological pH and the response was linear for the concentration of EP in the ranges 0.8-9.0 μM and 10.0-100 μM, with a detection limit of 8 × 10-7 M. The amperometric response of EP remains unaltered even in the presence of 50-fold excess of uric acid, ascorbic acid and 100-fold excess of l-Tryptophan, l-Tyrosine, l-Cysteine and Nicotinamide adenine dinucleotide. This sensor has shown stability, reproducibility, anti fouling effects and was successfully applied for the determination of EP in blood serum and adrenaline injection.