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This paper presents a sensitive simultaneous detection procedure for Sudan I and bisphenol A based on the multiwalled carbon nanotubes (MWCNTs)/Co3O4 nanocomposite modified screen-printed graphite electrode (SPGE). This MWCNTs/Co3O4 nanocomposite was prepared by the hydrothermal technique, and characterized by Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The electrochemical properties of MWCNTs/Co3O4 nanocomposite modified SPGE were analyzed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry (CHA), as well as linear sweep voltammetry (LSV). From the electrochemical results, a synergy between MWCNTs and Co3O4 nanoparticles (NPs) was detected as improved interfacial electron transfer, which was accompanied by a greater catalytic function for electrochemical oxidation of Sudan I. Based on the optimized condition, MWCNTs/Co3O4/SPGE exhibited the linear dynamic ranging between 0.05 and 600.0 μM detection of Sudan I with a limit of detection (LOD) 0.02 μM. Also, the as-prepared electrode was assessed for simultaneous detection of Sudan I and Bisphenol A. In the course of electrooxidation processes of these analytes, two complete peaks at 380 and 520 mV were observed on the modified electrode. At the end, utility of this new electrochemical sensor was performed to determine Sudan I and Bisphenol A in some real samples with good accuracy and precision.

A highly selective electrochemical sensor modified with CuFe2O4 nanoparticles and the ionic liquid was constructed for the detection of vanillin. The sensor could recognize vanillin from its analogs and possible coexistent substances. The response peak current and vanillin concen­tration showed a good linear relationship in the range of 0.01 - 300.0 μM, with a sensitivity of 0.0923 μA μM-1. The detection limit was 0.008 μM (S/N = 3). Besides, the reproducibility and stability measurements were also evaluated. It was applied to the determination of vanillin in real samples with satisfactory results.