A highly selective and simultaneous determination of ascorbic acid, uric acid and nitrite based on a novel poly-N-acetyl-l-methionine (poly-NALM) thin film

Abstract

This paper demonstrates the facile fabrication of an N-acetyl-L-methionine (NALM) polymer film on a glassy carbon electrode (GCE) by an electropolymerization technique. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrochemical techniques such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to characterize the modified electrode. This poly-NALM/GCE not only exhibits strong electrocatalytic activity towards the oxidation of ascorbic acid (AA), uric acid (UA) and nitrite with a shift in oxidation potential towards the less positive side, but also enhances peak current responses at physiological pH (7.2) conditions. Further, the overlapped anodic voltammetric peaks of the three analytes on a bare GC electrode were well-resolved into their independent oxidation peaks at the poly-NALM/GC modified electrode with a peak separation of 160 and 590 mV for AA–UA and UA–nitrite, respectively. Under the optimal experimental conditions, the anodic peak currents of AA, UA and nitrite increased linearly within the concentration ranges 10–1000 μM, 1–600 μM and 1–500 μM with correlation coefficients of 0.990, 0.996 and 0.994, respectively. The detection limits are 0.97, 0.34 and 0.75 μM for AA, UA and nitrite ion, respectively (S/N = 3). The modified electrode was successfully utilized to determine AA, UA and nitrite ion simultaneously in real samples such as human urine and tap water samples.