Indigo carmine is a commonly used industrial blue dye. To determine its concentration in a commercially available food dye composed of a mixture of indigo carmine and D-glucose, this paper characterizes it through (ATR, KBr) FTIR micro-Raman as well as UV/Vis and clock: Briggs–Rauscher (BR) oscillatory reaction methods. The indigo carmine was detected in the bulk food dye only by applying micro-Raman spectroscopy, indicating a low percentage of the indigo carmine present. This research provides an improvement in the deviations from the experimental Raman spectrum as calculated by the B97D/cc-pVTZ level of theory one, resulting in a better geometrical optimization of the indigo carmine molecule compared to data within the literature. The analytical curves used to determine indigo carmine concentrations (and quantities) in an aqueous solution of food dye were applied by means of UV/Vis and BR methods. BR yielded significantly better analytical parameters: 100 times lower LOD and LOQ compared to commonly used UV/Vis. The remarkable sensitivity of the BR reaction towards indigo carmine suggests that not only does indigo carmine react in an oscillatory reaction but also its decomposition products, meaning that the multiple oxidation reactions have an important role in the BR’s indigo carmine mechanism. The novelty of this research is the investigation of indigo carmine using a clock BR reaction, opening new possibilities to determine indigo carmine in other complex samples (pharmaceutical, food, etc.).

The aim of this study was to investigate the antioxidant capacity of fruit wines and their protective effects against hydrogen peroxide-induced oxidative stress in rat synaptosomes in vitro. The wines were produced from strawberries and drupe fruits (i.e., plum, sweet cherry, peach, and apricot) through microvinification with a pure S. cerevisiae yeast culture. Fruit wines were produced with and without added sugar before the start of fermentation, whereas subvariants with and without pits were only applied to drupe fruit wines. First, synaptosomes were treated with the wines, while oxidative stress was induced with H₂O₂. Subsequently, the activities of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)) and the content of malondialdehyde (MDA), an indicator of membrane injury, were determined. In addition, the Briggs–Rauscher reaction (BR) was used to evaluate the inhibition capacity against free radicals. All investigated fruit wines increased the activity of the studied antioxidant enzymes and decreased MDA content compared to the corresponding controls (synaptosomes treated with H₂O₂). After synaptosomal treatment with plum wine, the highest activities were observed for SOD (5.57 U/mg protein) and GPx (0.015 U/mg protein). Strawberry wine induced the highest CAT activity (0.047 U/mg protein) and showed the best ability to reduce lipid peroxidation, yielding the lowest MDA level (2.68 nmol/mg). Strawberry, plum, and sweet cherry wines were identified as samples with higher antioxidant activity in both principal component analysis (PCA) and hierarchical cluster analysis (HCA). Finally, plum wine exhibited the highest inhibitory activity in the BR reaction (397 s). The results suggest that fruit wines could be considered potential functional food due to their protective effects against oxidative stress.

In this work, we describe the crazy-clock phenomenon involving the state I (low iodide and iodine concentration) to state II (high iodide and iodine concentration with new iodine phase) transition after a Briggs–Rauscher (BR) oscillatory process. While the BR crazy-clock phenomenon is known, this is the first time that crazy-clock behavior is linked and explained with the symmetry-breaking phenomenon, highlighting the entire process in a novel way. The presented phenomenon has been thoroughly investigated by running more than 60 experiments, and evaluated by using statistical cluster K-means analysis. The mixing rate, as well as the magnetic bar shape and dimensions, have a strong influence on the transition appearance. Although the transition for both mixing and no-mixing conditions are taking place completely randomly, by using statistical cluster analysis we obtain different numbers of clusters (showing the time-domains where the transition is more likely to occur). In the case of stirring, clusters are more compact and separated, revealed new hidden details regarding the chemical dynamics of nonlinear processes. The significance of the presented results is beyond oscillatory reaction kinetics since the described example belongs to the small class of chemical systems that shows intrinsic randomness in their response and it might be considered as a real example of a classical liquid random number generator.

Tartrazine (E102), a synthetic azo dye, is extensively utilized across diverse industrial sectors. Understanding the mechanisms of tartrazine degradation and identifying its breakdown products are essential for assessing its environmental fate and potential health risks. Tartrazine is studied in this work in terms of: (i) determining its concentration in a commercial food dye by use the Briggs–Rauscher (BR) oscillatory (clock) reaction as seldom-employed analytical method, (ii) examining its degradation in a highly oxidative system, such as the BR oscillatory reaction, using Raman and FTIR spectroscopy, and (iii) monitoring the degradation process in the BR system at different magnifications using optical and scanning electron microscopy (SEM). The limits of detection (LOD) and quantification (LOQ) obtained for the BR reaction were higher than those determined by UV-Vis spectroscopy. Both methods determined comparable concentrations of tartrazine in the food dye. Based on the results obtained, the reaction mechanism for tartrazine degradation in the clock reaction was proposed. The findings strongly support the BR reaction as an easily available method for determining unknown concentrations of tartrazine in commercial food dyes. Furthermore, this study highlights the potential of the BR reaction for determining microconcentrations and for the rapid degradation of commercial food dyes.

In this study, a novel zinc-doped phosphor-tungsten salt (Zn-PWA) was synthesized via the Zn2+ ion exchange of protons in H3PW12O40 × nH2O, followed by controlled thermal transformation into its corresponding zinc phosphate-tungsten bronze (Zn-PWB) by sintering process. Thermo-gravimetric and differential thermal analysis (TGA/DTA) revealed that the phase transition from Zn-PWA into Zn-PWB occurs at 580°C, signaling a critical structural reorganization from a Keggin-type heteropoly salt lattice into an open-framework bronze structure. Structural and morphological characterization via X-ray powder diffraction (XRPD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) confirmed the preservation of the primary polyanionic structural units in Zn-PWA and the successful formation of the bronze phase after thermal treatment. The electrochemical properties by cyclic voltammetry (CV) of both materials were evaluated separately in aqueous LiNO3 solution. Comparative XRPD and electrochemical studies demonstrated that the thermally derived Zn-PWB exhibits highest crystallinity and significantly enhanced redox stability compared to its heteropoly salt precursor, as well as the highest capacity obtained compared to Fe-PWB and Co-PWB analogues.