Some limitations using optical sensors for determination of dissolved oxygen in wine (original) (raw)
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Sensors (Basel, Switzerland), 2018
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Development of a QCM-D biosensor for Ochratoxin A detection in red wine
Talanta, 2017
Ochratoxin A (OTA), a highly toxic compound, is one of the most widely spread mycotoxins that contaminates a large variety of agricultural commodities. Due to its presence in the food chain, it imposes a hazard on both human and animal health. Therefore, there is a need for precise, fast and simple methods for toxin quantification. Herein, a novel sensor based on a quartz crystal microbalance with dissipation monitoring (QCM-D) and antibodies for specific analyte recognition was developed for rapid and sensitive detection of OTA in red wine. The combination of indirect competitive assay with QCM-D gives a straightforward device, which can simultaneously measure frequency (Δf) and dissipation (ΔD) changes resulting in 2 detailed information about the mass attached to the sensor surface as well as conformational changes, viscoelastic properties and the hydration state of the film. Small molecules (such as OTA) suffer from poor LOD due to the high concentration of primary antibody needed to generate adequate signal. In the present study, amplification of the QCM-D signal was obtained by applying secondary antibodies conjugated with gold nanoparticles (AuNPs). Thanks to this, a linear detection range of 0.2-40 ng mL-1 has been achieved with an excellent LOD of 0.16 ng mL-1 , which is one order of magnitude lower than LOD specified by European Union legislation concerning the limit of OTA in food. Moreover, a matrix effect (caused by the occurrence of polyphenols in wine) and associated non-specific interactions with the sensor surface was completely eliminated by a simple pretreatment of the wine with the addition of 3% poly(vinylpyrrolidone) (PVP).
Food Control, 2019
We have developed a new method for the rapid and inexpensive determination of the total polyphenol index (TPI) in wines by simply immersing our sensory film in red or white wines and visually checking the colour change (qualitative analysis) or by analysing a photo taken of the film with a smartphone (quantitative analysis). This sensory material is straightforward and inexpensively prepared; it requires no monomer synthesis, is based on 100% commercially available monomers, and contains benzenediazonium salt motifs, which in the presence of phenols and/or polyphenol-based structures produce coloured diazo compounds. These sensory motifs are chemically anchored to the polymeric structure, and, accordingly, no migration of organic substances from the material occurs in the sensing process. Our method needs neither reagents nor sample pretreatment and has been contrasted with the standard TPI determination, i.e., measuring the absorbance of diluted wine at 280 nm, obtaining reliable data for white and red wines.
Sensing Free Sulfur Dioxide in Wine
Sensors, 2012
Sulfur dioxide (SO 2) is important in the winemaking process as it aids in preventing microbial growth and the oxidation of wine. These processes and others consume the SO 2 over time, resulting in wines with little SO 2 protection. Furthermore, SO 2 and sulfiting agents are known to be allergens to many individuals and for that reason their levels need to be monitored and regulated in final wine products. Many of the current techniques for monitoring SO 2 in wine require the SO 2 to be separated from the wine prior to analysis. This investigation demonstrates a technique capable of measuring free sulfite concentrations in low volume liquid samples in white wine. This approach adapts a known colorimetric reaction to a suspended core optical fiber sensing platform, and exploits the interaction between guided light located within the fiber voids and a mixture of the wine sample and a colorimetric analyte. We have shown that this technique enables measurements to be made without dilution of the wine samples, thus paving the way towards real time in situ wine monitoring.
Biosensors for the Polyphenolic Content of Wine Determination
Portugaliae Electrochimica Acta, 2007
Laccase of different lots was used in the construction of biosensors for the determination of polyphenolic content of wine. Laccase was immobilized on modified polyethersulfone membranes and applied to a Universal Sensor electrode base system. Parameters of the biosensors thus prepared were studied with respect to caffeic acid as the model substrate. Sensitivity of 0.102 mA × M −1 , RSD of 1.9%, linear range of 5 to 35 × 10-6 M, limit of detection of 8.8 × 10 −7 M, were determined. Different values of the applied potential near 0 V were tested in order to choose that one which gives the best performance of the present biosensors. Citrate and tartarate buffer solutions at pH 3.5 were used. Polyphenolic content of different red wines was determined at +100 mV vs. Ag/AgCl.
Biosensors and Bioelectronics, 2004
Research was carried out to experimentally evaluate the antioxidant capacity of several red and white wines using a superoxide dismutase (SOD) biosensor recently developed by the present authors. Measurements were performed by comparing the biosensor response to increasing concentration of the superoxide radical produced in solution by the xanthine/xanthine oxidase system, both in the presence and absence of the test sample. The results were compared with those of two traditional spectrophotometric methods and of a spectrofluorimetric method described in literature. Lastly, also the polyphenol, sulfite and ascorbic acid contents of the different wine samples examined were measured using a tyrosinase biosensor, a sulfite oxidase biosensor and an ascorbate oxidase biosensor, respectively.
A New Optic Fiber Sensor for Measuring the Concentration of Ethanol in Wine
Revista de Chimie -Bucharest- Original Edition-
This paper presents the development of a new optic fiber sensor for measuring ethanol concentration in real time, obtained by simultaneous immobilization of alcohol dehydrogenase and NAD + onto optical fiber by sol-gel technique in MTMOS/TEOS matrix. Biosensor was tested in a concentration range of 2-18% ethanol and the results were compared with standard spectrophotometric enzyme assay determinations, indicating that the sensor has a good functionality in the range of the analyzed concentrations.
Journal of Biochemical and Biophysical Methods, 2008
The possibility to use the photoluminescence of Ru(II) tris(4,7-diphenyl-1,10-phenathroline) dichloride, immobilized in sol-gel produced SiO 2 -based matrix for the determination of dissolved oxygen concentration in beer is studied. Organically-modified silane (octyltriethoxysilane) and mixtures from tetraethoxysilane and octyltriethoxysilane are used as precursors for matrix production. Spin-and dip-coating techniques are applied for films deposition. The predeposition ultrasound treatment of the sol ensures a good sensitivity and a linear sensor quenching response to oxygen in 1 ÷ 6 ppm O 2 -concentration interval. The CO 2 present practically has no effect on the films performance. Their photoluminescence show rather good stability on prolonged storage in beer.