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A comparison of the analytical characteristics of two tyramine biosensors, based on graphene oxide (GRO) and polyvinylferrocene (PVF) modified screen‐printed carbon electrodes (SPCE), is reported. Diamine oxidase (DAOx) or monoamine oxidase (MAOx) was immobilized onto the PVF/GRO modified SPCE to fabricate the biosensors. Surface characteristics and electrochemical behaviour of the modified SPCEs were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDX) and cyclic voltammetry (CV). Electrode surface composition and experimental variables such as pH and working potential were optimized in order to ensure a high performance. Under optimum experimental conditions, both DAOx/PVF/GRO/SPCE and MAOx/PVF/GRO/SPCE biosensors exhibited wide linear dynamic ranges for tyramine from 9.9×10−7 to 1.2×10−4 M and from 9.9×10−7 to 1.1×10−4 M, respectively. MAOx/PVF/GRO/SPCE biosensor showed higher sensitivity (11.98 μA mM−1) for tyramine determination than the DAOx/PVF/GRO/SPCE biosensor (7.99 μA mM−1). The substrate specifity of the biosensors to other biogenic amines namely histamine, putrescine, spermine, spermidine, tryptamine, β‐phenylethylamine and cadaverine was also investigated. The developed biosensors were successfully used for tyramine determination in cheese sample.

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In this study, a simple and sensitive electrochemical sensor based on Calix[4]arene-tren (Calix-tren) modified glassy carbon (GC) electrode was developed for the determination of Pb (II) ions. Electrochemical behavior of Calix-tren modified electrodes were investigated by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that Calix-tren modified GC electrode provides good electron transmission pathway than bare GC electrode. The amount of Pb (II) was determined by differential pulse anodic stripping voltammetric analysis as a sensitive detection technique. The experimental parameters such as pH, deposition time and deposition potential were optimized. The optimum pH value was selected as 7.0. The effect of deposition potential and deposition time on the peak current was tested and the optimum values were chosen as -1.2 V and 120 s, respectively. Under the optimal conditions, the working range of the developed sensor was determined as 0.48-2.31 µM, limit of detection (LOD) was 0.11 µM and the RSD obtained in the reproducibility study was 2.78 %. It was also found that the developed method could be used in the determination of Pb (II) ions in real samples with satisfactory results.

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