A metal-organic framework-based amperometric sensor for the sensitive determination of sulfite ions in the presence of ascorbic acid

Trends in pulse voltammetric techniques applied to foodstuffs analysis: The food additives detection

Food additives are chemical compounds intentionally added during foodstuff production to control technological functions, such as pH, viscosity, stability (color, flavor, taste, and odor), homogeneity, and loss of nutritional value. These compounds are fundamental in inhibition the degradation process and prolonging the shelf life of foodstuffs. However, their inadequate employment or overconsumption can adversely affect consumers' health with the development of allergies, hematological, autoimmune, and reproductive disorders, as well as the development of some types of cancer. Thus, the development and application of simple, fast, low-cost, sensitivity, and selectivity analytical methods for identifying and quantifying food additives from various chemical classes and in different foodstuffs are fundamental to quality control and ensuring food safety. This review presents trends in the detection of food additives in foodstuffs using differential pulse voltammetry and square wave voltammetry, the main pulse voltammetric techniques, indicating the advantages, drawbacks, and applicability in food analysis. Are discussed the importance of adequate choices of working electrode materials in the improvements of analytical results, allowing reliable, accurate, and inexpensive voltammetric methods for detecting these compounds in foodstuffs samples.

Transparent, flexible, and eco-friendly starch-based films for reversible optoelectronic noses for food spoilage monitoring in smart packaging

A reversible optoelectronic nose is presented consisting of ten acid-base indicators incorporated into a starch-based film, covering a wide pH range. The starch substrate is odorless, biocompatible, flexible, and exhibits high tensile resistance. This optical artificial olfaction system was used to detect the early stages of food decomposition by exposing it to the volatile compounds produced during the spoialge process of three food products (beef, chicken, and pork). A smartphone was used to capture the color changes caused by intermolecular interactions between each dye and the emitted volatiles over time. Digital images were processed to generate a differential color map, which uses the observed color shifts to create a unique signature for each food product. To effectively discriminate among different samples and exposure times, we employed chemometric tools, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). This approach detects food deterioration in a practical, cost-effective, and user-friendly manner, making it suitable for smart packaging. Additionally, the use of starch-based films in the food industry is preferable due to their biocompatibility and biodegradability characteristics.

Sensitive Electrochemical Sensor Based On an Aminated MIL-101(Cr) MOF for the Detection of Tartrazine

The aminated metal-organic framework H₂N-MIL-101(Cr) was used as the carbon paste electrode (CPE) modifier for the determination of tartrazine (Tz) in soft drinks. The amino material was characterized by electrochemical impedance spectroscopy and showed significantly faster electron transfer with lower charge-transfer resistance (0.13 kΩ) compared to the electrode modified with the unfunctionalized MIL-101(Cr) material (1.1 kΩ). The H₂N-MIL-101(Cr)-modified CPE [H₂N-MIL-101(Cr)-CPE] was then characterized by cyclic voltammetry (CV) using [Fe(CN)₆]^3- and [Ru(NH₃)₆]³⁺ ions as the redox probes, showing good accumulation of [Fe(CN)₆]^3- ions on the electrode surface. A CV scan of Tz in Britton Robinson buffer solution revealed an irreversible system with an oxidation peak at +0.998 V versus Ag/AgCl/KCl. Using CV and differential pulse voltammetry, an electrochemical method for quantifying Tz in aqueous medium was then developed. Several parameters that affect the accumulation and detection steps were optimized. Optimal detection of Tz was achieved after 180 s of accumulation in Britton Robinson buffer solution (pH 2) using 2 mg of H₂N-MIL-101(Cr) material. Under optimal conditions, the sensor exhibited a linear response in the concentration range of 0.004-0.1 μM and good detection sensitivity (35.4 μA μM^-1), and the detection limit for Tz was found to be 1.77 nM (S/N = 3). Satisfactory repeatability, stability, and anti-interference performance were also achieved on H₂N-MIL-101(Cr)-CPE. The sensor was applied to commercial juices, and the results obtained were approximately similar to those given by UV-vis spectrophotometry.