Polyethylenimine-Multi-Walled Carbon Nanotubes/Glassy Carbon Electrode as an Efficient Sensing Platform for Promethazine

Abstract

A sensor based on polyethylenimine-functionalized multi-walled carbon nanotubes/glassy carbon electrode (fMWCNT-PEI/GCE) was developed for promethazine hydrochloride (PMZ) detection in pharmaceutical samples. PMZ is oxidized at the modified electrode at more negative potentials and with higher sensitivity than at the bare electrode. The morphological characterization of the sensor surface showed a homogeneous layer with size distribution of the diameters of the PEI-fMWCNT ranging from 22–47 nm. The characterization of the electrochemical behavior suggested that an equal number of electrons and protons participate in the PMZ irreversible oxidation on the fMWCNT-PEI/GCE. The optimized conditions were Sörensen buffer at pH 2.0, frequency of 90 s−1, amplitude of the pulse of 40 mV, and height of the potential step of 2 mV. Based on the most sensitive peak, at ca. −0.75 V, which is related to the formation of the phenazothiazonium ion, the PMZ calibration curve was obtained with sensitivity of 3.21 × 10−3 A mol−1 l, a linearity range of 4.97 × 10−7 to 5.03 × 10−6 mol l−1, and a detection limit of 2.31 × 10−7 mol−1 l. This methodology was successfully validated in pharmaceutical samples by comparison with the standard method of the Pharmacopoeia, showing high potential applicability of the fMWCNT-PEI/GCE.