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In this work, an electrochemical sensor for the azo dye compound tartrazine (TRT) determination was proposed. A screen-printed carbon electrode (SPCE) was modified by depositing three-dimensional porous reduced graphene oxide decorated with carbon quantum dots and platinum nanoparticles (Pt/CQDs@rGO/SPCE). The resulting amount of TRT was observed by differential pulse voltammetry. Under optimal conditions, the sensor exhibited two wide linearities ranging from 0.01 to 1.57 μM and 1.57–9.3 μM with the reliability coefficient of determination of 0.991 and 0.992, respectively. The detection limit (LOD) was also estimated to be 7.93 nM. Moreover, the Pt/CQDs@rGO/SPCE suggested high selectivity in the presence of several interfering agents and azo dye compounds that have a similar structure. Additionally, the Pt/CQDs@rGO/SPCE revealed superior recovery values of about 96.5–101.6% for candy, 99.7–103.5% for soft drinks, 96.0–101.2% for jelly powder, and 98.0–103.0% for water samples. Furthermore, the fabricated sensor exhibits excellent selectivity, stability, reproducibility, and repeatability, indicating a great perspective in the monitoring of TRT. Therefore, it can be speculated that the proposed electrode could be effectively applied to determine TRT in food samples.

Background: Antioxidants are one of the important additives in food samples due to their role in protecting human cells against the effects of free radicals. The analysis of antioxidants is essential due to the role of antioxidants in improving body health. Objective: A square wave voltammetric sensor was fabricated for the determination of tert-butylhydroxyanisole (TBHA) based on the application of CdO/SWCNTs and 1-methyl-3-butylimidazolium chloride as mediators for the modification of carbon paste electrode (MBCl/CdO/SWCNTs/CPE). The MBCl/CdO/SWCNTs/CPE improved the sensitivity of TBHA ~ 6.7 times and showed a linear dynamic range 0.07-600 µM with detection limit 0.02 µA for the analysis of TBHA. The pH investigation confirmed that electro-oxidation of TBHA occurred by exchanging two electrons and two protons. In addition, the MBCl/CdO/SWCNTs/CPE was used for determination of TBHA in food samples.

This work demonstrates the fabrication of a carbon paste electrode containing NiO/CNTs modified with 1-methyl-3-butylimidazolium bromide as the binder (CPE/1-M-3BIBr/NiO/CNTs), and its applications related to the highly sensitive detection of carmoisine. The CPE/1-M-3BIBr/NiO/CNTs system was successfully utilized for the nanomolar determination of carmoisine at pH = 7.0. The CPE/1-M-3BIBr/NiO/CNTs successfully resolved the oxidation signals of carmoisine and tartrazine with a peak separation of 450 mV. This is the first time that an application of an electrochemical sensor for the simultaneous determination of carmoisine and tartrazine, two important azo dyes, has been reported. In addition, wide dynamic linear concentration ranges (70–650 μM for carmoisine and 0.1–750 μM for tartrazine), low detection limits (20 nM for carmoisine and 0.06 μM tartrazine) and excellent reproducibility were reported. The CPE/1-M-3BIBr/NiO/CNTs were successfully used for the analysis of carmoisine and tartrazine in dried fruit and soft drink samples.

A carbon paste electrode modified with 1-methyl-3-butylimidazolium bromide and CuO decorated single-wall carbon nanotubes (1-M-3-BIBr/CuO/SWCNTs/CPE) was utilized for nanomolar determination of amaranth in the presence of nitrite using square wave voltammetric (SWV) method. The structure of CuO/SWCNTs was investigated by SEM method. 1-M-3-BIBr/CuO/SWCNTs/CPE exhibited an enhancement in electro-oxidation current and active surface area. Also, 1-M-3-BIBr/CuO/SWCNTs/CPE exhibited indicated high catalytic activity toward the electro-oxidation of amaranth and simultaneous determination of it in the presence of nitrite. The 1-M-3-BIBr/CuO/SWCNTs/CPE achieved dynamic ranges 0.004–750 μM and 1.0–10,000 μM between the oxidation currents and the concentration of amaranth and nitrite, respectively. We obtained the detection limit of 1.0 nM and 0.5 μM for amaranth and nitrite, respectively. The 1-M-3-BIBr/CuO/SWCNTs/CPE was successfully applied to analysis of amaranth and nitrite in foodstuffs.