A nanocomposite based on multi-walled carbon nanotubes grafted by molecularly imprinted poly(methacrylic acid–hemin) as a peroxidase-like catalyst for biomimetic sensing of acetaminophen

Abstract

In the present study the synthesis of a nanocomposite based on multi-walled carbon nanotubes grafted by poly(methacrylic acid–hemin) is described. The presence of functional groups in the nanocomposite was evaluated by FT-IR, while morphological, textural and thermal stability data were evaluated by means of SEM, TEM, nitrogen adsorption–desorption assays and TGA, respectively. The material was evaluated as a biomimetic and catalytic sensor toward the electrochemical determination of acetaminophen (AC) by depositing it onto a glassy carbon electrode surface. Acetaminophen has been widely used as an analgesic and antipyretics drug and for patients with a high sensitivity to aspirin; therefore the development of analytical methods for AC determination in pharmaceutical formulations is of paramount importance for quality control. The biomimetic electrochemical sensor operation is similar to that of the biosensor based on horseradish peroxidase, where the hemin in the presence of H₂O₂ catalyses the oxidation of acetaminophen into N-acetyl-p-benzoquinoneimine, which in turn is reduced back to AC on the electrode at a potential of −0.27 V. The variables that exert influence on the performance of the biomimetic response, including H₂O₂ concentration (300 μmol L⁻¹), pH (8.0) and concentration (0.1 mol L⁻¹) and type of buffer solution (Trizma) were investigated. Under optimized conditions the electrochemical determination of AC using multi-walled carbon nanotubes grafted by poly(methacrylic acid–hemin) immobilized on the surface of the glassy carbon electrode was carried out by square wave voltammetry (SWV), showing a limit of detection of 1.1 μmol L⁻¹. The selectivity of material, ascribed to imprinted effect, was assured by comparison to a non-imprinted material (NIP). The proposed method was applied to AC determination in a pharmaceutical formulation, whose obtained values were very similar to those declared and statistically equal to the HPLC method, thus illustrating the feasibility of method for analysis of real samples.