Determination of histamine in wines with an on-line pre-column flow derivatization system coupled to high performance liquid chromatography

A new rapid and sensitive high performance liquid chromatography (HPLC) method for determining histamine in red wine samples, based on continuous flow derivatization with 1,2-naphthoquinone-4-sulfonate (NQS), is proposed. In this system, samples are derivatized on-line in a three-channel flow manifold for reagent, buffer and sample. The reaction takes place in a PTFE coil heated at 80 degrees C and with a residence time of 2.9 min. The reaction mixture is injected directly into the chromatographic system, where the histamine derivative is separated from other aminated compounds present in the wine matrix in less than ten minutes. The HPLC procedure involves a C18 column, a binary gradient of 2% acetic acid-methanol as a mobile phase, and UV detection at 305 nm. Analytical parameters of the method are evaluated using red wine samples. The linear range is up to 66.7 mg L(-1) (r = 0.9999), the precision (RSD) is 3%, the detection limit is 0.22 mg L(-1), and the average histamine recovery is 101.5% +/- 6.7%. Commercial red wines from different Spanish regions are analyzed with the proposed method.     

Dispersive liquid-liquid microextraction using non-chlorinated, lighter than water solvents for gas chromatography-mass spectrometry determination of fungicides in wine

A novel and low solvent consumption method for the sensitive determination of fungicide residues in wine samples is proposed. Analytes were extracted by dispersive liquid-liquid microextraction (DLLME) and further determined by gas chromatography-mass spectrometry (GC-MS). Under optimized conditions, a binary mixture of acetone and 1-undecanol (0.5 and 0.05 mL, respectively) was used to extract target compounds from diluted (1:1) wine samples. After centrifugation, the floating phase of 1-undecanol was solidified and separated from the liquid hydro-alcoholic matrix. Thereafter, it was allowed to melt at room temperature and injected in the GC-MS system. The method showed relative standard deviations (RSDs, %) below 13%, limits of quantification (LOQs) between 0.2 and 3.2 ng mL(-1) and linear responses for concentrations up to 300 ng mL(-1). The efficiency of the liquid-phase microextraction process was scarcely affected by the characteristics of wine samples, consequently pseudo-external standard calibration (using matrix matched standards of red and white wine) sufficed to achieve acceptable accuracy values: relative recoveries from 81 to 120%. The applicability of the method was demonstrated with commercial wine samples.     

Quantitative determination of wine highly volatile sulfur compounds by using automated headspace solid-phase microextraction and gas chromatography-pulsed flame photometric detection. Critical study and optimization of a new procedure

The quantitative determination of wine volatile sulfur compounds by automated headspace solid-phase microextraction (HS-SPME) with a carboxen-polydimethylsiloxane (CAR-PDMS) fiber and subsequent gas chromatography-pulsed flame photometric detection (GC-PFPD) has been evaluated. The direct extraction of the sulfur compounds in 5 ml of wine has been found to suffer from matrix effects and short linear ranges, problems which could not be solved by the use of different internal standards or by multiple headspace SPME. These problems were attributed to saturation of the fiber and to competitive effects between analytes, internal standards and other wine volatiles. Another problem was the oxidation of analytes during the procedure. The reduction in sample volume by a factor 50 (0.1 ml diluted with water or brine) brought about a reduction in the amount of sulfur compounds taken in the fiber by a factor just 3.3. Consequently, a new procedure has been proposed. In a sealed vial containing 4.9 ml of saturated NaCl brine, the air is thoroughly displaced with nitrogen, and the wine (0.1 ml) and the internal standards (0.02 ml) are further introduced with a syringe through the vial septum. This sample is extracted at 35 degrees C for 20 min. This procedure makes a satisfactory determination possible of hydrogen sulfide, methanethiol, ethanethiol, dimethyl sulfide, diethyl sulfide and dimethyl disulfide. The linear dynamic ranges cover the normal ranges of occurrence of these analytes in wine with typical r2 between 0.9823 and 0.9980. Reproducibility in real samples ranges from 10 to 20% and repeatability is better than 10% in most cases. The method accuracy is satisfactory, with errors below 20% for hydrogen sulfide and mostly below 10% for the other compounds. The proposed method has been applied to the analysis of 34 Spanish wines.     

Development of a SPME-GC-ECD methodology for selected pesticides in must and wine samples

A method for the determination of some pesticide residues in must and wine samples was developed using solid-phase microextraction (SPME) and gas chromatography-electron capture detection (GC/ECD). The procedure only needs dilution as sample pre-treatment and is therefore simple, fast and solvent-free. Eight fungicides (vinclozolin, procymidone, iprodione, penconazole, fenarimol, folpet, nuarimol and hexaconazole), one insecticide (chlorpyriphos) and two acaricides (bromopropylate and tetradifon) can be quantified. Good linearity was observed for all the compounds in the range 5-100 microg/L. The reproducibility of the measurements was found acceptable (with RSD's below 20%). Detection limits of 11 microg/L, on average, are sufficiently below the proposed maximum residue limits (MRL's) for these compounds in wine. The analytical method was applied to the determination of these compounds in Portuguese must and wine samples from the Demarcated Region of Alentejo, where any residues could be detected.     

Development of a SPME-GC-ECD methodology for selected pesticides in must and wine samples

A method for the determination of some pesticide residues in must and wine samples was developed using solid-phase microextraction (SPME) and gas chromatography – electron capture detection (GC/ECD). The procedure only needs dilution as sample pre-treatment and is therefore simple, fast and solvent-free. Eight fungicides (vinclozolin, procymidone, iprodione, penconazole, fenarimol, folpet, nuarimol and hexaconazole), one insecticide (chlorpyriphos) and two acaricides (bromopropylate and tetradifon) can be quantified. Good linearity was observed for all the compounds in the range 5–100 μg/L. The reproducibility of the measurements was found acceptable (with RSD’s below 20%). Detection limits of 11 μg/L, on average, are sufficiently below the proposed maximum residue limits (MRL’s) for these compounds in wine. The analytical method was applied to the determination of these compounds in Portuguese must and wine samples from the Demarcated Region of Alentejo, where any residues could be detected.     

Multiple headspace solid-phase microextraction for eliminating matrix effect in the simultaneous determination of haloanisoles and volatile phenols in wines

This paper proposes a multiple headspace solid-phase microextraction (MHS-SPME) method coupled to gas chromatography-tandem mass spectrometry detection (GC/MS/MS) for the simultaneous determination of 2,4,6-trichloroanisole, 2,3,4,6-tetrachloroanisole, pentachloroanisole, 2,4,6-tribromoanisole, 4-ethylphenol, 4-ethylguaiacol, 4-vinylphenol and 4-vinylguaiacol in wines. These compounds are involved in the presence of "cork taint" and Brett character in wines. The MHS-SPME method is a modification of SPME developed for quantitative analysis that avoids possible matrix effects based on an exhaustive analyte extraction from the sample. After demonstrating the existence of matrix effect in the analysis of the target compounds by HS-SPME with a divinylbenzene/Carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibre, the MHS-SPME method was developed and validated. The proposed method showed satisfactory linearity, precision and detection limits, all below the odour detection thresholds of the compounds in wine matrices. Good recoveries were observed for all compounds, always above 90%, and the repeatability obtained was considered acceptable, ranging between 2 and 11%. After checking the applicability of the method by comparing the results recorded with those obtained with the standard addition method, the method was applied successfully to the analysis of wine samples. To our knowledge, this is the first time that MHS-SPME combined with GC/MS/MS has been applied to simultaneously determine haloanisoles and volatile phenols in wine.     

Autoanalyzer for continuous fractionation and quantitation of the polyphenols content in wines

A simple continuous flow autoanalyzer for the on-line fractionation of the polyphenols content in wines is proposed. The target compounds are isolated from the matrix by solid-phase extraction on an RP-C18 sorbent column, using selective solvents for the sequential elution of each polyphenol family. Moreover, evaporative light scattering detection (ELSD) is used for the first time for the on-line monitorization of the three polyphenol fractions present in the wine samples. Thus, a single sample injection is required to determine the global concentration of the three selected polyphenol fractions and the whole analysis is completed within a few minutes. Three calibration graphs were constructed for quantitative analysis of the global compounds concentration in every fraction and covered the range 5-300 mg l(-1) (expressed as gallic acid). Average repeatability, expressed as relative standard deviation, was 4%. The proposed autonalyzer was applied to the analysis of a variety of commercial wine samples. The results obtained were compared with those provided by the Folin-Ciocalteau method, being similar in all instances.     

Optimization of ultrasound assisted-emulsification-dispersive liquid-liquid microextraction by experimental design methodologies for the determination of sulfur compounds in wines by gas chromatography-mass spectrometry

A new method was developed for analyzing sulfur compounds in the aroma of white wines using ultrasound assisted-emulsification-dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry detection. In the present work, the analytical method for simultaneous determination of seven sulfur compounds (methylmercaptoacetate, methyl(methylthio)acetate, 2-methylthioethanol, 3-methylthiopropanol, 3-methylthiohexanol, 4-methylthio-4-methyl-2-pentanone and hexanethiol) is reported. Parameters that affect the efficiency of the methodology such as extracting and dispersing solvents, sample volume, ion strength, cavitation time and centrifugation time were investigated using a fractionated factorial 2^6-1 (R = V) screening design. Then, the factors presenting significant positive effects on the analytical response (extracting volume, ion strength, cavitation time and centrifugation time) were considered in a further central composite design to optimize the operational conditions for the ultrasound assisted-emulsification-dispersive liquid-liquid microextraction procedure. Additionally, multiple response simultaneous optimization by using the desirability function was used to find the optimum experimental conditions. The best results were obtained using pH sample 4.25, extractant volume 150 μL, ionic strength 8.75% NaCl, cavitation time 20 s and centrifugation time 50 s. The use of the optimized ultrasound assisted-emulsification-dispersive liquid-liquid microextraction technique allowed to obtain the best extraction results with the minimum interference from other substances from the matrix, and it allowed to quantify the analytes in white wine samples by calibration graphs. Recoveries ranging from 91.99% to 125.87% for all sulfur compounds proved the accuracy of the proposed method in white wine samples. Method detection limits were in the range of 0.36-1.67 ng mL⁻¹ and limits of quantitation were between 0.63 and 3.02 ng mL⁻¹ for sulfur compounds in white wine samples. The proposed methodology was successfully applied for the determination concentrations of sulfur compounds in different commercial Chardonnay wine samples from Mendoza, Argentine.     

Determination of Brett character responsible compounds in wines by using multiple headspace solid-phase microextraction

This study presents a method based on the use of multiple headspace solid-phase microextraction (MHS-SPME) for the quantitative analysis of 4-ethylphenol, 4-ethylguaiacol, 4-vinylphenol and 4-vinylguaiacol. MHS-SPME is a modification of SPME that implies several consecutive extractions from the same sample and avoids possible matrix effects. This study demonstrates the existence of a matrix effect in the analysis of compounds responsible for Brett character in wine when an HS-SPME based method is used with a carbowax/divinylbenzene (CW/DVB) fibre. For this reason, MHS-SPME is proposed as an alternative technique with respect to HS-SPME. The method proposed was validated and the detection limits obtained were 0.06 microg/l for 4-ethylguaiacol and 4-ethylphenol and, 0.20 microg/l for 4-vinylguaiacol and 0.12 microg/l for 4-vinylphenol. These detection limits are below the odour detection thresholds of the compounds in wine matrices. The repeatability obtained, in terms of relative standard deviation (RSD), was considered acceptable, ranging from 1 to 12%. To evaluate the applicability of the proposed MHS-SPME method, concentration results were compared with those obtained with the standard addition method, and the results were similar with both methods. Furthermore, the new method was satisfactorily applied to a number of commercial red, white and rosé wines. Therefore, MHS-SPME can be considered as an alternative to avoid the matrix effect in wine samples.     

Determination of Procymidone, Pentachloroaniline and Methyl-pentachloro-phenylsulfide Residues in Wine by MSPD-GC-ECD

A rapid method based on matrix solid-phase dispersion (MSPD) was developed for the determination of procymidone, pentachloroaniline and methyl-pentachloro-phenylsulfide in wine. After the optimisation of different parameters such as the type of adsorbent, the extraction solvent, and the extraction assistance by sonication. The analysis of samples was accomplished using gas chromatography with electron-capture detector (GC-ECD). Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. The recovery of the method was in the range 82.4–93.7% and a good linear relationship (R ² ≥ 0.9992) with relative standard deviations lower than 8%. The limits of detection (LOD) ranged from 0.1 to 0.4 μg L^?1. The proposed method was applied to the analysis of these compounds in commercial wine samples.     

Determination of minor and trace volatile compounds in wine by solid-phase extraction and gas chromatography with mass spectrometric detection

A new method for the quantitative determination of important wine odorants has been developed. The wine (50 ml) is extracted in a 200 mg solid-phase extraction (SPE) cartridge filled with Lichrolut-EN resins from Merck. The elution is carried out with 1.3 ml of dichloromethane. These extracts are directly analyzed by GC-Ion Trap-MS without further concentration. Twenty-seven important wine odorants, such as volatile phenols, vanillin derivatives, aliphatic lactones, nor-isoprenoids, minor esters and terpenols, can be quantitatively determined in a single gas chromatography-mass spectrometry (GC-MS) run. The recoveries in the SPE isolation are in good agreement with those expected from the calculation of breakthrough volumes from solid-liquid distribution coefficients and are higher than 90%, except for guaiacol, vanillin, 2,6-dimethoxyphenol and 4-vinylphenol. In most cases, precision is below 10%. Method linearity is satisfactory, with r2 higher than 0.99 in all cases. The analysis of spiked samples has shown that there is good agreement between the real mass of compound added to the wine and that determined by analysis. In all cases detection limits are below the odor detection threshold of the compounds, and the calibrated interval covers the natural range of occurrence of the compounds in wine.     

Fast analysis of important wine volatile compounds development and validation of a new method based on gas chromatographic-flame ionisation detection analysis of dichloromethane microextracts

A method for the simultaneous determination of major (10-200 mg/l) and minor (0.1-10 mg/l) volatile compounds from wine has been optimised and validated. A 3-ml volume of wine is diluted with water (7 ml), salted with 4.5 g of ammonium sulfate and extracted with 0.2 ml of dichloromethane. The extract is injected in the split mode in a GC system, separated on a Carbowax 20M capillary column and detected by flame ionisation detection. Volatiles from wine are divided into four groups according to their behaviour in the extraction, and a specific internal standard has been selected for each group. The method allows satisfactory determination of more than 30 volatile compounds of wine. Compounds analysed include acetaldehyde, diacetyl, acetoine (3-hydroxy butanone), fusel alcohols and their acetates, and fatty acids and their ethyl esters. The linear dynamic range of the method covers the normal range of occurrence of analytes in wine and extends from at least one magnitude order to more than two, with typical r2 between 0.9938 and 0.9998. Reproducibility ranges from 3.1 to 10% (as RSD) with 5.5% as the average. The analysis of spiked samples has shown that matrix effects do not significantly affect method performance.     

Sequential injection system for the spectrophotometric determination of reducing sugars in wines

A sequential injection system for the spectrophotometric determination of reducing sugars in wines is described. The methodology is based on the formation of a coloured complex produced by the reaction of copper (I) with 2,9-dimethyl-1,10-phenanthroline (neocuproine), after reduction of copper (II) to copper (I) by reducing sugars. In the present SI system, a dialysis unit was incorporated not only to allow the sample dilution, but also to minimise the interference of some coloured compounds. In this way, direct sample introduction into the system was possible, without any previous treatment of the wine samples. The proposed method can be applied to the determination of reducing sugars in two concentration ranges: from 2 to 25 g l(-1) (table wines) and from 20 to 140 g l(-1) (Port wines). To perform determinations in these two ranges, the manifold configuration remained the same; just a few operational parameters were changed in the controlling software. A sampling-rate of 14-18 samples per hour was obtained with good repeatability for ten consecutive injections of wine samples (relative standard deviations (RSD) <2.1%). The results obtained from 19 wine samples were comparable to those obtained by the reference method.     

Development of headspace solid-phase microextraction-gas chromatography-mass spectrometry methodology for analysis of terpenoids in Madeira wines

A dynamic headspace solid-phase microextraction methodology was developed for analysis of varietal aroma compounds in must and Madeira wine samples, a spirit wine with an ethanol content of 18% (v/v). The factors with influence in the headspace solid-phase microextraction efficiency such as: fibre coating, extraction time and temperature, pH, ionic strength, ethanol content, desorption time and temperature, were optimised and the method validated. The best results were obtained for a 85 μm polyacrylate fibre, with a 60 min headspace for must and 120 min for wine samples, in a 2.4 ml sample at 40 °C with 30% of NaCl. The extract is injected in the splitless mode in a GC-MS Varian system, Saturn III, and separated on a Stabilwax capillary column. The linear dynamic range of the method covers the normal range of occurrence of analytes in wine with typical r² between 0.985 (β-ionone) and 0.998 (linalool) for musts and between 0.980 (α-terpineol) and 0.999 (linalool) for must and wine samples, respectively. For must samples the reproducibility ranges from 2.5% (citronellol) to 14.4% (nerolidol) (as R.S.D.), and from 4.8% (citronellol) to 14.2% (nerolidol) for wine samples. The analysis of spiked samples has shown that matrix effects do not significantly affect method performance. Limits of detection obtained are in low μg l⁻¹ range for all compounds analysed in this study.     

Microextraction of volatile compounds from wine samples and their determination by GC-FID. The effect of the salts and extraction solvents used

Summary This study describes the optimization of microextraction as a method for extracting volatile compounds from wine. The study has been applied to twelve compounds present in wine: 3-methylbutyl acetate, 3-methyl-1-butanol, ethyl hexanoate, hexanol, ethyl octanoate, butanoic acid, ethyl decanoate, diethyl succinate, hexanoic acid, phenylethanol, octanoic acid, and decanoic acid. These compounds were selected from those identified by GC-MS analysis of a real wine sample. By means of a synthetic wine, the study investigated the influence on extraction yield of the solvents and salts used, the proportion of salts, and the agitation time. The determination was performed by GC with flame ionization detection and an internal standard was used for quantification. The method was applied to samples of white wine from La Rioja.     

Rapid Separation of Antioxidants in Food Samples by Coelectroosmotic CE

Rapid separation of a group of eight antioxidants by coelectroosmotic capillary electrophoresis and their preliminary determination in foods (cereal, wine, and beer) is described. The compounds studied were protocatechuic acid, salicylic acid, p-hydroxybenzoic acid, vanillic acid, syringic acid, p-coumaric acid, ferulic acid, and sinapic acid. The best separation was achieved by use of a running buffer consisting of 125 mM boric acid, 49 mM disodium hydrogen phosphate, 0.002% (w/v) hexadimethrine bromide, and 2.5 mM α-cyclodextrin, at pH 7.5; the analysis time was less than 3.5 min. Ligration time and peak area reproducibility, studied on the same day (n=4) and on three different days (n=12), showed the method is reproducible. A study of the antioxidant content of cereal, wine, and beer samples was conducted to evaluate the usefulness of the method. Antioxidants were extracted from cereal samples by sonication with methanol and from wine and beer samples by solid-phase extraction with C₁₈ cartridges. This preliminary study showed that seven of the eight compounds could be detected in wine and cereal samples whereas only five were detected in beer samples.     

Optimisation of a dispersive liquid-liquid microextraction method for the simultaneous determination of halophenols and haloanisoles in wines

A dispersive liquid-liquid microextraction (DLLME) method has been optimised for simultaneously extracting 2,4,6-trichloranisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA), 2,4,6-tribromoanisole (TBA), pentachloroanisole (PCA), 2,4,6-trichlorophenol (TCP), 2,3,4,6-tetrachlorophenol (TeCP), 2,4,6-tribromophenol (TBP) and pentachlorophenol (PCP) from wine. The haloanisoles and halophenols were automatically determined using a gas chromatography-electron-capture detection (GC-ECD) system. Derivatisation of halophenols was performed at the same time as DLLME. Firstly, disperser and extraction solvents, salt addition and temperature conditions were selected. Then, the volume of disperser solvent, extraction solvent and derivatisation agent, and the percentage of base were optimised by means of a central composite design combined with desirability functions. The optimal extraction-derivatisation conditions found were 1.3 mL of acetone, 150 μL of carbon tetrachloride, 75 μL of acetic anhydride and a percentage of base of 0.7%; with no salt addition and at room temperature. Under these conditions, the proposed method showed satisfactory linearity (with correlation coefficients over 0.994), repeatability (below 9.7%) and reproducibility (below 9.9%). Moreover, detection limits were lower than the olfactory threshold of the compounds. The developed method was successfully applied to the analysis of red wine samples. To our knowledge, this is the first time that DLLME has been applied to determine cork taint responsible compounds in wine.     

Optimization of detection conditions and single-laboratory validation of a multiresidue method for the determination of 135 pesticides and 25 organic pollutants in grapes and wine by gas chromatography time-of-flight mass spectrometry

This paper describes single-laboratory validation of a multiresidue method for the determination of 135 pesticides, 12 dioxin-like polychlorinated biphenyls, 12 polyaromatic hydrocarbons, and bisphenol A in grapes and wine by GC/time-of-flight MS in a total run time of 48 min. The method is based on extraction with ethyl acetate in a sample-to-solvent ratio of 1:1, followed by selective dispersive SPE cleanup for grapes and wine. The GC/MS conditions were optimized for the chromatographic separation and to achieve highest S/N for all 160 target analytes, including the temperature-sensitive compounds, like captan and captafol, that are prone to degradation during analysis. An average recovery of 80-120% with RSD < 10% could be attained for all analytes except 17, for which the average recoveries were 70-80%. LOQ ranged within 10-50 ng/g, with < 25% expanded uncertainties, for 155 compounds in grapes and 151 in wine. In the incurred grape and wine samples, the residues of buprofezin, chlorpyriphos, metalaxyl, and myclobutanil were detected, with an RSD of < 5% (n = 6); the results were statistically similar to previously reported validated methods.     

Individual and simultaneous enzymatic determination of ethanol and acetaldehyde in wines by flow injection analysis

The individual and simultaneous enzymatic determination of ethanol and acetaldehyde in wine by flow injection analysis is described. Individual determinations of 0.002–0.016% (v/v) ethanol or 1.0–8.0 μg ml^?1 acetaldehyde with r.s.d. 0.7% and 0.5%, respectively, are done with a single-beam spectrophotometer, based on the use of alcohol dehydrogenase and aldehyde dehydrogenase. A diode-array detector and dual reagent injections are used for the simultaneous determination of the two compounds. The errors are 〈 3.5% and 〈 2.0% for ethanol and acetaldehyde, respectively, when the method is applied to wine samples.     

Simultaneous Determination of Phenolic Compounds in Red Wines by HPLC‐UV

Abstract

Ten samples of commercially Italian red wines were analyzed in order to determine the phenolic content. Variations in wine types are largely due to differences in concentration and composition of these compounds. Polyphenolic compounds are a large and complex group of substances which constitute one of the most important quality parameters of wine. These constituents of red wine contribute to organoleptic characteristics and to antioxidant and anti‐inflammatory properties. Moderate wine consumption is associated with several beneficial physiological effects, which include anticancer activities, inhibition of platelet aggregation, and inhibition of LDL oxidation which constitutes the initial stage of the pathogenesis of arteriosclerosis.

For the analysis, reversed‐phase high performance liquid chromatography (HPLC) method coupled with UV‐Vis detection was used. The method uses a gradient elution to identify nine biologically active phenolic constituents: catechin; epicatechin; trans‐ and cis‐resveratrol; gallic, chlorogenic and caffeic acid; rutin and quercetin in red wine samples. The samples are injected directly without any pretreatment. The method is simple, fast, not expensive and shows good linearity for all constituents, and the detection limits ranged from 0.3–1.6 µg/ml for trans‐resveratrol and gallic acid, respectively. Moreover, the samples were analyzed in different times for estimation of stability of these compounds.