Chromatographic Analysis of Trans Resveratrol in Italian Wines: Comparisons between FL, UV and MS Detection

Resveratrol (3,5,4′-trihydroxystilbene) is a phytoalexin that belongs to the group of stilbenes, known to occur in grapes and consequently in grape products. Its presence in wine is an important qualitative parameter because of the several beneficial effects on human health. The aim of this work is the development of a high-performance liquid chromatographic (HPLC) method for the determination of trans resveratrol in wines, and comparisons between the results obtained by different detection techniques: UV-vis spectroscopy, fluorescence spectroscopy and mass spectrometry. Resveratrol is analysed on a C-18 column using gradient elution. The method permits direct injection of sample, revealing to be time-saving, overcoming the need of sample pre-treatment steps. Detection limits were 154.8 ng mL⁻¹ by HPLC-UV, 118.0 ng mL⁻¹ by HPLC-FL and 48.0 ng mL⁻¹ by HPLC-MS. Trans resveratrol has been then quantified in a group of 52 wines derived from different Italian regions, cultivars and winemaking technologies by HPLC-UV.     

Use of the internal standardization for difficult sampling by graphite furnace atomic absorption spectrometry

This work shows the potentiality of As as internal standard to compensate errors from sampling of sparkling drinking water samples in the determination of selenium by graphite furnace atomic absorption spectrometry. The mixture Pd(NO₃)₂/Mg(NO₃)₂ was used as chemical modifier. All samples and reference solutions were automatically spiked with 500 μg l⁻¹ As and 0.2% (v/v) HNO₃ by the autosampler, eliminating the need for manual dilutions. For 10 μl dispensed sample into the graphite tube, a good correlation (r=0.9996) was obtained between the ratio of analyte absorbance by the internal standard absorbance and the analyte concentrations. The relative standard deviations (R.S.D.) of measurements varied from 0.05 to 2% and from 1.9 to 5% (n=12) with and without internal standardization, respectively. The limit of detection (LD) based on integrated absorbance was 3.0 μg l⁻¹ Se. Recoveries in the 94-109% range for Se spiked samples were obtained. Internal standardization (IS) improved the repeatability of measurements and increased the lifetime of the graphite tube in ca. 15%.     

Development of a Sequential Injection Analysis Device for the Determination of Total Polyphenol Index in Wine

A sequential injection analysis method is developed for the determination of the total polyphenol index in wines. The determination is based on the Folin-Ciocalteu reaction, which is monitored spectrophotometrically. Interactions between experimental variables and their optimal levels were investigated using factorial designs. The proposed system is fully computerised and is able to monitor polyphenol index in real samples of white, sweet and red wines. The calibration graph is linear from 5 to 200mg·L^–1 using Tannic acid as standard, with a detection limit of 3.2mg·L^–1. Interferences are studied. For validation purposes the proposed methodology was applied to the determination of the total polyphenol index in different types of wines and compared with earlier alternatives in order to assess their performance.     

Amperometric Detection of Ethanol Vapors by Screen Printed Electrodes Modified by Paper Crowns Soaked with Room Temperature Ionic Liquids

A convenient assembly recently proposed for screen printed gold electrodes (SPEs) suitable for measurements in gaseous samples is here tested for the analysis of the ethanol content in alcoholic drinks. This assembly involves the use of a circular crown of filter paper, soaked in the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hydrogen sulfate, which is simply placed upon a disposable screen printed cell, so as to contact the outer edge of the gold disc working electrode, as well as peripheral counter and reference electrodes. The electrical contact between the paper crown soaked in RTIL and the SPE electrode is assured by a gasket and all components are installed in a polylactic acid holder. This assembly provides a portable and disposable electrochemical platform, assembled by the easy immobilization onto a porous and inexpensive supporting material such as paper of a RTIL characterized by profitable electrical conductivity and negligible vapor pressure. The electroanalytical performance of this device was assayed for the flow injection analysis of the ethanol concentration in some real samples of wine and beer and the results obtained are compared with the alcoholic degree reported in the relevant bottle-labels, thus highlighting a substantially satisfactory agreement. Repeatable sharp peaks (RSD=6–8 %) were detected for ethanol over a wide linear range (1–20 % v/v in water) and a detection and quantitation limit of 0.55 % v/v and 1.60 % v/v were inferred for a signal-to-noise ratio of 3 and 10, respectively.     

Determination of monomethylmercury in low- and high-polluted sediments by microwave extraction and gas chromatography with atomic fluorescence detection

Laser tomography techniques were used in order to make visible the flow patterns induced by ascending bubbles in flutes poured with champagne. The stability of flow patterns was investigated in flutes showing natural (without any specific surface treatment) as well as artificial effervescence (i.e., engraved at their bottom), all along the first 15 min after pouring. Engravement conditions were found to strongly influence the kinetics and the stability with time of the mixing flow phenomena found in champagne glasses.     

Phenolic natural products of the wines obtained from three new Merlot clone candidates

This work aimed to evaluate the total contents of polyphenolics (the Ribereau-Gayon–Maurié procedure), anthocyanins (using pH differential method) and tannins (the Nègre procedure) as well as the content of phenolic acids (using UPLC/MS chromatography), respectively of the wines obtained from three new Merlot clone candidates in the perennial clonal selection. The aforementioned chemical parameters were determined in the samples covering the period 2009–2012. In comparison both with the standard Merlot wine (mother vine) and the wines obtained from other two clone candidates, the Merlot wine of the clone candidate No. 022 was found to have the highest total content of all three examined components 1.89 ± 0.05 g/L (polyphenolics), 185.59 ± 5.00 mg/L (anthocyanins) and 1.11 ± 0.03 g/L (tannins), as well as six phenolic acids including gallic acid (25.49 ± 0.27 mg/L). These findings are in good agreement with the observed trend for the viticultural parameters indicating the clone candidate No. 022 as more promising than mother.     

线性扫描阳极溶出伏安法测定酒中的铅

采用线性扫描阳极溶出伏安法测定酒中铅的含量，在0．1mol/L盐酸底液中，铅的加标回收率为97．4％～101．3％，测定结果的相对标准偏差为0．76％～3．32％，线性范围为0．02～1．10mg／L。     

Evaluation of Italian wine by the electronic tongue: recognition, quantitative analysis and correlation with human sensory perception

The electronic tongue based on a sensor array comprising 23 potentiometric cross-sensitive chemical sensors and pattern recognition and multivariate calibration data processing tools was applied to the analysis of Italian red wines. The measurements were made in 20 samples of Barbera d’Asti and in 36 samples of Gutturnio wine. The electronic tongue distinguished all wine samples of the same denomination and vintage, but from different vineyards. Simultaneously the following quantitative parameters of the wines were measured by the electronic tongue with precision within 12%: total and volatile acidity, pH, ethanol content, contents of tartaric acid, sulphur dioxide, total polyphenols, glycerol, etc. The electronic tongue is sensitive to multiple substances that determine taste and flavour of wine and, hence, the system was capable of predicting human sensory scores with average precision of 13% for Barbera d’Asti wines and 8% for Gutturnio wines.     

Phenolic Composition and Total Antioxidant Capacity by Electrochemical,Spectrophotometric and HPLC‐EC Evaluation in Portuguese Red and White Wines

Phenolic composition and in vitro total antioxidant capacity have been evaluated, in red and white Portuguese wines, by electrochemical methods, spectrophotometric methods, and reverse‐phase high performance liquid chromatography with electrochemical detection (HPLC‐EC). The different phenolic compounds present in seventeen red and white wines, with different grape varieties, and from different geographical locations, were successfully identified and detected. The wines in vitro total antioxidant capacity, using the method of capture of diphenilpicrilhydrazil (DPPH^.) free radical “efficient concentration” (EC₅₀), and the electrochemical quantitative index (EI), was determined. The wine with the highest total antioxidant capacity exhibited the lowest antioxidant power, and the EI and EC₅₀ assays had a very good correlation.     

Recognition of adulteration of Italian wines by thin-film multisensor array and artificial neural networks

The paper reports the use of a chemoresistive multisensor array for recognition of some adulterated Italian wines (two white, four red, two rosè) added with methanol, ethanol or other same-colour wine. A multisensor array constituted by four thin-film semiconducting metal oxide sensors, surface-activated by Pt, Au, Pd, Bi metal catalysts, has been used to generate the chemical pattern of the volatile compounds present in the wine samples. The responses of the multisensor array towards wines tested by headspace sampling have been evaluated. Multivariate analysis including principal component analysis (PCA) as well as back-propagation method trained artificial neural networks (ANNs) have been applied to analytical data generated from the multisensor array to identify both the adulteration of wines and to determine the added content of adulterant agent of methanol or ethanol up to 10 vol.%. The cross-validated ANNs provide the highest achieved percentage of correct classification of 93% and the highest achieved correlation coefficient of 0.997 and 0.921 for predicted-versus-true concentration of methanol and ethanol adulterant agent, respectively.