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A new method to manufacture electrochemical devices based on the graphite and colorless nail polish (N-grap) film was developed for tartrazine (Tz) detection. Scanning Electron Microscopy (SEM) demonstrates that the composite material presents a high porous carbon structure. Cyclic voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) were employed to electrochemically characterize the electrode material, which corroborates the porous structure of the N-graph due to the enhanced electroactive area (5.4-fold increase) and presented a heterogeneous electron transfer rate constant (k0) of 5.82 × 10−3 cm s−1 for potassium ferricyanide. The electrochemical determination of the Tz was carried out using square-wave voltammetry (SWV), under the optimized experimental conditions, which showed high sensitivity (0.793 A L mol−1) and a lower limit of detection (LOD) of 2.10 × 10−8 mol L−1 with a linear concentration ranging from 2.0 to 50.0 μmol L−1. The developed sensor was applied for the analysis of Tz in sports drink samples and the result obtained by N-grap device was statistically compared with a spectrophotometric method demonstrating good accordance and the accuracy of the proposed method. Based on these results, we believe that this new fabrication method to produce disposable and low-cost electrochemical devices can be an alternative method for in-field analysis of dye in commercial sport drink samples and other relevant applications. [Display omitted] • A simple method to fabricate disposable and low-cost electrochemical devices using graphite and nail polish is reported. • The composite material presented a porous carbon structure that exhibits high electron transfer kinetics. • The proposed sensor was successfully applied to the sensitive analysis of tartrazine (Tz) in sports drink samples. • The proposed method is reproducible, robust, accurate, and suitable for routine analysis. [ABSTRACT FROM AUTHOR]

• MeP is the most common paraben, its use can cause cancer and hormonal problems. • Side effects have been observed due to the bioaccumulation of these compounds. • Breast milk has an average of 22.0 μg L−1 of MeP. • Electrochemical sensor and the analytical method have very close results. The sustained use of cosmetics, hygiene products and medicines containing methylparaben (MeP) can be related to cases of cancer in women and children, which is why it is important to develop simple ways to monitor this compound. Gold electrodes were modified with Layer-by-Layer (LbL) films of magnetite nanoparticles (MNP) and polypyrrole (Ppy) for electrochemical determination of MeP. To investigate the synergistic effect between the MNP and Ppy, three different LbL architectures were tested: multilayers of Ppy with an conventional polycation poly(allylamine hydrochloride) – Au/(PAH/Ppy) 3 , MNP with a conventional polyanion poly(vinyl sulfonic acid) – Au/(MNP/PVS) 3 and the hybrid composite film Au/(MNP/Ppy) 3. The highest oxidation current and lowest oxidation potential were achieved by the Au/(MNP/Ppy) 3 electrode in a range up to 131.4 μmol L−1 with a limit of detection of 9.95 × 10−8 mol L−1. The performance of the electrochemical sensor was statistically investigated by the Miller-Miller method demonstrating accuracy comparable to an analytical method (capillary electrophoresis). MeP was determined in urine, breast milk and cosmetic with recovery values varying from 84.0% to 113.3%. [ABSTRACT FROM AUTHOR]