Study of spectral analytical data using fingerprints and scaled similarity measurements

A new chemoinformatic model has been developed for enlarging the differences between spectra and applied to differentiation of wines according to the criteria grape origin and variety and ageing process. The model is based on generation of fingerprints from normalised spectra, using empirical parameters and a set of 120 samples. After generation of the fingerprints, similarity matrixes were built on the basis of the Tanimoto similarity index between the fingerprints of the samples. Calculation of the Tanimoto index was modified to adapt the index to the characteristics of the analytical measurements. Thus, scaling factors taking into account pattern fingerprints generated from a group of samples with common characteristics were used. In addition, a modified expression for calculating the Tanimoto index was employed. Principal-components analysis (PCA) and soft independent modelling of class analogy (SIMCA) were applied to the similarity matrixes. The results obtained are discussed as a function of the normalisation method employed, the empirical factor used in generation of the fingerprints, and selection of samples for building the pattern fingerprint, etc. Finally, results from differentiation of wines are compared with those obtained by applying PCA to the unprocessed spectra as stated by the proposed model.     

Rapid fingerprinting of red wines by MALDI mass spectrometry

Here we report a simple and fast method for wine fingerprinting based on direct matrix-assisted laser desorption/ionization (MALDI) mass spectrometry analysis of different red wine samples, useful for batch-to-batch analysis and for the detection of key compounds even in trace amounts which may vary from vintage to vintage, and from one treatment to another one. A series of 20 samples from different wines were subjected to MALDI mass spectrometry. We found that 2,5-dihydroxybenzoic acid is far superior with respect to all the matrices tested To the best of our knowledge this is the first application of an effective wine profiling not limited to detection of anthocyanins. More than 80 molecular species were detected. Moreover, qualitative and quantitative differences were observed, owing to the nature and relative abundance of different chemical compounds among the wines.     

Exploiting the bead injection LOV approach to carry out spectrophotometric assays in wine: application to the determination of iron

A sequential injection lab-on-valve (SI-LOV) system was used to develop a new methodology for the determination of iron in wine samples exploiting the bead injection (BI) concept for solid phase extraction and spectrophotometric measurement. Nitrilotriacetic Acid (NTA) Superflow resin was used to build the bead column of the flow through sensor. The iron (III) ions were retained by the bead column and react with SCN⁻ producing an intense red colour. The change in absorbance was monitored spectrophotometrically on the optosensor at 480 nm. It was possible to achieve a linear range of 0.09-5.0 mg L⁻¹ of iron, with low sample and reagent consumption; 500 μL of sample, 15 μmol of SCN⁻, and 9 μmol of H₂O₂, per assay. The proposed method was successfully applied to the determination of iron in wine, with no previous treatment other than dilution, and to other food samples.     

Characterization of low-molecular weight peptides in champagne wine by liquid chromatography/tandem mass spectrometry

This paper reports the use of an on-line LC–ESI–MS/MS method for the identification and quantification of di- and tripeptides in champagne wine without laborious sample pretreatment. The identification of these compounds, in their underivatised form, is based on identical retention times and ESI–MS spectra to those of reference standards. The presence of nine dipeptides (Arg–Ile, Ile–Arg, Ile–Val, Lys–Phe, Lys–Tyr, Phe–Lys, Tyr–Gln, Tyr–Lys, Val–Ile) and the absence of two tripeptides (Phe–Arg–Arg and Lys–Met–Asn) have been evidenced in the matrix. Calibration curves for each analyte were established using Phe–Arg as internal standard. The calibration curves were linear in the concentration range 0.1–10 mg L⁻¹ with a determination coefficient, r², better than 0.992. The accuracy for the calibration standard was estimated at between 92 and 102%. This method allows high recovery and satisfies the necessary requirements with respect to accuracy, repeatability and sensitivity. The first application of this analytical method to the measurement of di- and tri-peptides in different vintages of champagne wine is reported. Compositional changes in the peptides occurred depending on the vintage.     

Determination of the carboxylic acids in acidic and basic process samples by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) with indirect UV detection was used in developing a method for the simultaneous determination of inorganic anions, aliphatic and heterocyclic organic acids in various processed samples. The analytes were determined simultaneously in 10 min using an electrolyte containing 20 mM 2,3-pyrazine dicarboxylic acid, 65 mM tricine, 2 mM BaCl₂, 0.5 mM cetyltrimethylammonium bromide, and 2 M urea at pH 8.06. Linear plots for the analytes were obtained in the concentration range of 2–150 mg L⁻¹. Relative standard deviations (RSDs) of peak areas during a 3-day analysis period varied from 5.5% for glycolate to 9.5% for oxalate. RSDs of migration times varied between 0.4% and 1.1%. The detection limit (at S/N 3) was 1 mg L⁻¹ for all the analytes studied. The proposed method was successfully demonstrated for the determination of carboxylic acids in eight oxygen treated samples of commercial softwood and hardwood kraft lignin and two red wine samples of Pinot Noir grapes. In the kraft lignin samples the concentrations of carboxylic acids correspond to the oxidation time. The acid concentrations of wine varied considerable.     

Application of tandem column solid phase extraction and flame atomic absorption spectrometry for the determination of inorganic and organically bound forms of iron in wine

A tandem column solid phase extraction (SPE) procedure has been devised to examine the fractionation of Fe in wine. Wine was filtered through a 0.45 μm filter and then, the filtrate was driven through an adsorbing Amberlite XAD-7HP column followed by a cation exchange Dowex 50W-x8-200 column. Three different Fe groupings are discriminated and assessed, including hydrophobic species of Fe bound to phenolic substances and related species (phenolic fraction), cationic species comprising simple Fe ions and labile Fe forms (cationic fraction), in addition to anionic and/or neutral Fe complexes with organic acids (residual fraction). The suitability of the procedure has been evaluated analyzing four bottled red wines. The results obtained were verified using another tandem column assemblage in which an adsorbing Amberlite XAD-16 column was exchanged by the Amberlite XAD-7HP column. The fractionation pattern ascertained for Fe in analyzed wines is discussed in reference to previously published works. In addition, a conditioning treatment and preparation of Amberlite XAD resins have been revised.     

Determination of fungicides in wine by mixed-mode solid phase extraction and liquid chromatography coupled to tandem mass spectrometry

A novel procedure for the determination of nine selected fungicides (metalaxyl-M, azoxystrobin, myclobutanil, flusilazole, penconazole, tebuconazole, propiconazole, diniconazole and difenoconazole) in wine samples is presented. Sample enrichment and purification is simultaneously performed using mixed-mode, anion exchange and reversed-phase, OASIS MAX solid-phase extraction (SPE) cartridges. Analytes were determined by liquid chromatography coupled to tandem mass spectrometry using atmospheric pressure electrospray ionization (LC-ESI-MS/MS). Parameters affecting the chromatographic determination and the extraction-purification processes were thoroughly investigated. Under optimized conditions, 10 mL of wine were firstly diluted 1:1 with ultrapure water and then passed through the mixed-mode SPE cartridge at a flow of ca. 5 mLmin(-1). After a washing step with 5 mL of an aqueous NH(4)OH solution (5%, w:v), analytes were recovered with just 1 mL of methanol and injected in the LC-MS/MS system without any additional purification. The selective extraction process avoided significant changes in the ionization efficiency for red and white wine extracts in comparison with pure standards in methanol. Performance of the method was good in terms of precision (RSDs<11%) and accuracy (absolute recoveries>72%, determined against pure standards in methanol) reporting method LOQs in the range of 0.01-0.79 ngmL(-1) for target compounds, which are far below the EU maxima residue levels (MRLs) for fungicides in vinification grapes and wine. Several commercial wines from different geographic areas in Spain were analyzed. In most samples, metalaxyl-M and azoxystrobin were found at concentrations up to several ngmL(-1).     

乙酰丙酮吸光光度法测定白酒中甲醇含量

乙酰丙酮法测定白酒中甲醇是一种新的测试方法。白酒样品用高锰酸钾氧化后，加草酸除去过量的氧化剂，在pH3～4范围内，加入乙酰丙酮溶液，在沸水浴中显色，于418nm波长处测量其吸光度。方法步骤简单，具有较高的灵敏度和较高的重现性。     

Bismuth Modified Gold Microelectrode for Pb(II) Determination in Wine Using Alkaline Medium

Electrodeposition of bismuth on gold microelectrodes for determination of Pb(II) by square wave anodic stripping voltammetry (SWASV) was accomplished by an in situ procedure in alkaline solution. A linear calibration plot for Pb(II) in the concentration range 40 to 6700 nmol L^?1 (r=0.998) was obtained, the detection limit was found to be 12.5 nmol L^?1 (S/N=3) and the relative standard deviation in solutions containing 1 μmol L^?1 Pb(II) was 4% (n=12). The analytical performance of the proposed sensor was tested by measuring the Pb(II) concentration in a wine sample. The result was in good agreement with the one obtained by GFAAS.