Highly sensitive determination of gallic acid on poly (L-Methionine)-carbon nanotube composite electrode

In this work, composite electrode was prepared with poly L-methionine and carbon nanotube (PLM/MWCNT) onto glassy carbon electrode. The composite electrode surface morphology and electrical properties were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Electrochemical response of Gallic acid (GA) on PLM/MWCNT/GCE was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and amperometry. The results demonstrated that PLM/MWCNT/GCE exhibit a favorable application for the determination of GA in pH 2.2 Britton-Robinson buffer solution. The prepared composite electrode offered two linear segments for GA in DPV over the range of 4.0 nmoL L-1 -1.1 mu mol L-1 and 1.7 mu mol L-1 - 20.0 mu mol L-1 with a detection limit of 3.1 nmol L-1 (S/N = 3). The amperometric detection was also used for improving as lower detection limit compare with DPV. The detection limit was calculated from the amperometric studies found as 0.5 nmol L-1. Through the synergistic effect of PLM and MWCNT, the composite electrode exhibits good catalytic effect, selectivity, stability and reproducibility for GA. The proposed method was verified by successful determination of GA in green tea, black tea and wine samples