This study discusses the design, development, and construction of a low cost optical multisensor system. The light sources in the proposed system are lanthanide(III) complexes emitting light in the near infrared spectral region. Through the ability to adjust the source wavelength these measuring platform can be used for a variety of practical tasks. The feasibility of the developed devices has been demonstrated for analysis of milk samples.

Hydrogen peroxide (H₂O₂) is widely used aqueous solution for oxidation, disinfection and sterilization, and its detection is very important in the fields of biological health and environment. The main detection methods of H₂O₂ include colorimetric, electrochemical, enzymatic and fluorescence analysis. However, due to the influence of moisture and oxidation, it is very scarce to realize the simple, convenient, real-time and efficient detection technology for hydrogen peroxide vapor (HPV). Recently, our group proposed to add ammonium titanyl oxalate (ATO) to the sensing film composite system to prepare a chemosensor based on PEDOT:PSS-ATO/PEDOT composite film, and explored the influence of various material systems on its HPV sensing performance both giving electrical and colorimetric response. This study was expected to realize a practical HPV sensor as well as promote the further application of PEDOT-based composites in the field of chemosensors.

The objective of our work is to provide an advantage for designing new,
more efficient sensors using undoped ZnO nanowires. Nanostructures based
on ZnO have demonstrated improved sensor performance, thanks to their
excellent chemical and thermal stability, as evidenced by their high
melting temperature.

We have utilized the Schottky defect model to simulate the behavior of
free carriers in ZnO semiconductors. Additionally, we have investigated
the theoretical model of oxygen molecule adsorption and desorption.
Furthermore, we have examined the adsorption of reducing gases, with
acetone gas being used as an example.

By employing the Comsol software, we have discovered that the solid-gas
interaction is significantly reduced at a temperature of 295 °C for ZnO
nanowires compared to bulk ZnO, which typically requires a temperature
of 500 °C. This reduction can be attributed to the predominant behavior
of the side surfaces (101 ̅0) in ZnO nanostructures, as well as the lower
activation energy of these surfaces compared to the (0002) surfaces.
These ZnO nanowire nanostructures provide numerous active and
thermodynamically favorable surfaces for the adsorption of reducing
gases. The simulation method using Comsol is one of the means to achieve
improved design and offer optimal device operation.

The possibilities of using mid-infrared (IR) spectroscopy in combination with the method of attenuated total reflection (ATR) to analyse the quality of dairy products are shown. Application of chemometrics [1], in particular, the curve resolution method (MCR) to spectral data of the milk drop drying process allows us to obtain spectra of its individual components and make quantitative estimates of the sample composition [2].

In this study, a portable desktop analyzer for determination of fat content in milk is introduced. A prototype of the sensor consists of three light emitting diodes (red, green, and blue) as a light source. The transmitted light is detected by a photoresistor and continuous voltage measurements provided by the microcontroller, is recorded by a computer. The resulting univariate and multivariate models show that the developed analytical device is capable to determinate fat content in raw and homogenized milk with sufficient accuracy.

Heavy metal ions in drinking water result from industrialization and can cause a nuisance to the environment. Due to their toxicity and carcinogenic tendencies toward humans, determining heavy metal ions remains challenging. This study focuses on creating a cutting-edge electrochemical sensor with unprecedented sensitivity to lead (Pb (II)). In present investigation, we have hydrothermally produced lanthanum porous coordination polymer (La-TMA), which was further modified with Cr nanoparticles, characterized with structural, morphological, electrochemical and spectroscopic techniques, and used as a sensing material. The differential pulse voltammogram pattern of the Cr@La-TMA sensor indicates an affinity for Pb(II). All sensing parameters have been investigated: sensitivity, selectivity, repeatability, reproducibility, and linearity. The Cr@La-TMA sensor shows selectivity towards Pb(II), which is validated by the interference study for various analytes such as Cd(II), Hg(II), Cu(II), Cr(II), and Fe(II). The sensor exhibited excellent linearity for the concentration range of 1 nM to 10 nM with a limit of detection of 1 nM, which is below the MCL level suggested by the US-EPA and WHO. Furthermore, Cr@La-TMA was also validated for tap water samples, which confirms the sensor's viability. The proposed sensor would be incredibly useful for the real-time monitoring of heavy metal ions.

Actinidia genus comprises 54 species and 21 varieties of which A. chinensis var. chinensis and A. chinensis var. deliciosa are the most commercialized ones. The nutritional properties of kiwifruit have prompted their global production to nearly reach the value of 4.5 million tons per year, being Asia one of the top producers. This increment in their production has raised a parallel augment of associated organic wastes, especially when kiwifruits are used for processed products. The most abundant by-products obtained include skins, seeds, and discarded fruits. This biomass has a huge potential for its high content of bioactive compounds, such as dietary fiber or polyphenols. Therefore, it has been targeted by the food industry as a sustainable and cost-effective source of natural ingredients, highly demanded by consumers. Indeed, kiwi skins and seeds have been pointed out as a relevant source of pectin followed by the kiwi pulp. Pectin is a recognized ingredient due to the organoleptic properties it may confer but also for its prebiotic capacities. The recovery of pectin has been mainly performed by the application of extraction techniques that implied the use of chemical reagents such as acids. Nowadays, the use of chemicals is negatively regarded for their associated side effects. Indeed, customers' claims for chemical-free food ingredients have triggered the development and application of green extraction techniques: ultrasonic, microwave, enzyme, supercritical fluid, or electrical pulse. Pectin has been successfully extracted with these green techniques both in terms of yield and quality, improving results obtained with traditional extraction techniques. Therefore, the main objective of this work is to review the wide variability of green techniques applied to extract pectin along with the comparison of the optimal parameters as basis for the future development of an optimized extraction method. Besides, this work also aims to disclose the potential of kiwifruit by-product as a source of pectin and their industrial applications for the development of functional foods, nutraceuticals, food additives or cosmetics.

High Performance Liquid Chromatography (HPLC) with ultraviolet/visible (UV/Vis) or diode array detection (DAD) is routinely used for drug quantification in R&D all around the world. However, it may lack the sensitivity required for bioanalytical studies. On the other hand, HPLC with fluorescence detection (FLD) is a cost-effective alternative that significantly increases drug signal, allowing the detection of compounds at very low concentrations. Pitavastatin is a lipid-lowering drug that contains the structure of quinoline, a highly fluorescent molecule. Recently, it has gained interest due to its promising antitumoral activity over different types of cancer [2].

Bearing this in mind, an HPLC-FLD method was herein developed and validated for the quantification of pitavastatin in human plasma, according to the ICH M10 guideline [1]. Overall, a signal gain of 54-70 times was achieved when using fluorescence vs UV detection. Sample preparation included a one-step protein precipitation with acetonitrile, followed by centrifugation and filtration prior to injection. Pitavastatin was separated from endogenous matrix interferents using a C₁₈ column and applying a gradient elution. Atorvastatin was used as internal standard. Accordingly, the method was shown to be selective, specific, and sensitive, with the lower limit of quantification of 3 ng/mL and a complete absolute and relative recoveries above 94 %. The method was linear over the concentration range of 3 – 900 ng/mL (r² > 0.998), accurate (bias < 7.15 %) and precise (RSD < 9.63 %). This method allows the therapeutic monitoring of patients treated with pitavastatin but can also support novel clinical studies of this drug in human plasma.

[1] ICH – International Council for Harmonisation (2022). ICH Guideline M10 on Bioanalytical Method Validation and Study Sample Analysis, 1-45.
[2] Jiang, W., Hu, J. W., He, X. R., Jin, W. L., & He, X. Y. (2021). Statins: a repurposed drug to fight cancer. Journal of Experimental & Clinical Cancer Research, 40, 1-33.

The development of optical sensors for monitoring the food freshness during the storage and transportation helps to increase the food security and the customer satisfaction by preventing the misinterpretation of food-date labelling. In this study, a simple and low cost paper-based optical sensor was fabricated for visual detection of the food spoilage by naked eye. The filter paper was coated with the electrically conductive polyaniline ink. The pH-responsiveness of the coated polyaniline nanofibers allowed for the colorimetric detection of the shrimp spoilage through the transition from the doped green emeraldine acid form state to the dedoped blue emeraldine base state. The combination of the filter paper and the ink of polyaniline nanofibers represent a facile and quick method for the fabrication of colorimetric optical sensors for food freshness monitoring applications

Tea and herbal infusions are the most consumed non-alcoholic beverages worldwide and possess bioactive components with multiple health benefits. They are categorized in different classes that depend on: the elaboration process, origin, and components. Commonly, analytical methods are employed to classify tea according to its a chemical composition by liquid and gas chromatography-mass spectrometry, among others. Novel methods, such as electronic noses (e-noses) effectively provide real-time and objective monitoring of odors for extended periods of time. This work aimed to classify 8 different types of tea (green, white, black, spearmint, mint, hibiscus, lemongrass, chamomile) using two feature extraction methods and two pattern recognition analyses that were compared. A total of 34 tea samples were analyzed by e-nose consisting of a sample handling system as olfactometer, seven chemo-resistive gas sensors, and a 12-bit analog-to-digital converter. Tea samples were measured 10 times to ensure repeatability, resulting in database of 340 tea measures with 2499 samples each per sensor.

Data were pre-processed using Principal Component Analysis (PCA) and Parallel Factor Analysis (PARAFAC). The information extracted was classified by Artificial Neural Network (ANN) and k-nearest neighbor (k-NN). The best architecture in ANN and distance in k-NN were demonstrated by 10 k-fold cross-validation. The classification rate was 93% in ANN and PCA, 73% in ANN and PARAFAC, 94% in k-NN and PCA, and 84% in k-NN and PARAFAC. This demonstrates that conventional PCA is better than complex PARAFAC.