Silica graphite as an ink additive for stencil printed electrodes: A novel approach for electroanalytical determination of sulfanilamide

Abstract

Silica-graphite composites present a high surface area, mechanical and chemical stability, and high functionality to be applied in electrochemical sensing. Indeed, those materials have been successfully employed to build composite electrodes such as carbon paste electrodes for a wide range of applications. Despite excellent performance, this kind of electrodes have been replaced by stencil printed electrodes (SPEs), emerging as a scalable alternative for manufacture offering sensors disposables, low-cost, customizable, and miniaturized. Based on this, herein a novel silica-graphite (SiG) composite is described as an ink additive aiming scalable production of SPEs with high functionality and surface area. The SPE as well as SiG were characterized by electrochemical impedance spectroscopy, scanning electron microscopy, thermogravimetric analysis, and contact angle. After an accumulation step, SiG-SPE pretreated has shown a significant improvement on oxidation of sulfanilamide compared with unmodified SPE. Electrochemical surface activation and pre-concentration conditions were investigated to enhance sensitivity and selectivity. Under optimized conditions, silica-graphite stencil printed electrode (SiG-SPE) was employed for the electrochemical determination of sulfanilamide by using square wave-adsorptive stripping voltammetry (SWAdSV). It was possible to achieve a linear dynamic range (LDR) from 2 to 20 mmol L−1 with a limit of detection (LOD) and quantification (LOQ) of 0.34 and 1.13 mmol L−1, respectively. The stability of the sensors was evaluated over five weeks, and a decrease of around 5.5 % in response was observed compared to fresh electrodes. SiG-SPE also presented high selectivity and low matrix interference for sulfanilamide determination with a recovery range of 96.2–100.1 % for urine and 98.2–106.1 % for commercial fat milk. Those results suggest that SiG is a promising ink additive for the production of low-cost and high-performance sensors, showing enhanced analytical properties, mechanical resistance, and chemical stability.