Sensitized synchronous fluorimetric determination of trans-resveratrol and trans-piceid in red wine based on their immobilization on nylon membranes

It has been carried out the determination of trans-resveratrol and trans-piceid in red wine samples by using room temperature synchronous fluorescence, sensitized through their retention on nylon membranes, in front-face mode. These compounds are weakly fluorescent in solution but their retention allows using the native fluorescence of these compounds as analytical signal, due to the increase in the medium rigidity. To determine these compounds in red wine, a previous liquid-liquid extraction is necessary and in the case of trans-resveratrol it is also necessary a previous cleanup stage using C18 cartridges. Diethylether and ethyl acetate are the selected extractant solvents for trans-resvertarol and trans-piceid, respectively. The retention on nylon membranes was carried out by immersion of the membranes in solutions of these compounds. Variables involved in the retention and measurement processes were optimized, and the analytical figures of merit were obtained under optimal conditions. Ethanol:water 10:90 v:v and ethyl acetate were the solvents used for the retention of trans-resveratrol and trans-piceid, respectively and, for each case a immersion time of 300 and 600 s was selected. Satisfactory linear relation between fluorescence intensity and concentration was found in the intervals 0.040 and 0.242 mg L⁻¹ of trans-resvertarol and 0.009 and 0.288 mg L⁻¹ of trans-piceid. Concentration of 1.08 ± 0.21 mg L⁻¹ for trans-resveratrol and 1.49 ± 0.36 mg L⁻¹ for trans-piceid were found in a wine sample obtained from a pool of commercial red wines.     

Thermal stability of high surface area silicon carbide materials

The synthesis of mesoporous silicon carbide by chemical vapor infiltration of dimethyl dichlorosilane into mesoporous silica SBA-15 and subsequent dissolution of the silica matrix with HF was investigated. The influence of the synthesis parameters of the composite material (SiC/SBA-15) on the final product (mesoporous SiC) was determined. Depending on the preparation conditions, materials with specific surface areas from 410 to 830 m² g⁻¹ and pore sizes between 2 and 10 nm with high mesopore volume (0.31-0.96 cm³ g⁻¹) were prepared. Additionally, the thermal stability of mesoporous silicon carbide at 1573 K in an inert atmosphere (argon) was investigated, and compared to that of SBA-15 and ordered mesoporous carbon (CMK-1). Mesoporous SiC has a much higher thermal textural stability as compared to SBA-15, but a lower stability than ordered mesoporous carbon CMK-1.     

Determination of total polyphenol index in wines employing a voltammetric electronic tongue

This work reports the application of a voltammetric electronic tongue system (ET) made from an array of modified graphite-epoxy composites plus a gold microelectrode in the qualitative and quantitative analysis of polyphenols found in wine. Wine samples were analyzed using cyclic voltammetry without any sample pretreatment. The obtained responses were preprocessed employing discrete wavelet transform (DWT) in order to compress and extract significant features from the voltammetric signals, and the obtained approximation coefficients fed a multivariate calibration method (artificial neural network-ANN-or partial least squares-PLS-) which accomplished the quantification of total polyphenol content. External test subset samples results were compared with the ones obtained with the Folin–Ciocalteu (FC) method and UV absorbance polyphenol index (I₂₈₀) as reference values, with highly significant correlation coefficients of 0.979 and 0.963 in the range from 50 to 2400 mg L⁻¹ gallic acid equivalents, respectively. In a separate experiment, qualitative discrimination of different polyphenols found in wine was also assessed by principal component analysis (PCA).     

Modified mesoporous silica materials for on-line separation and preconcentration of hexavalent chromium using a microcolumn coupled with flame atomic absorption spectrometry

A modified SBA-15 mesoporous silica material NH₂-SBA-15 was synthesized successfully by grafting γ-aminopropyl-triethoxysilane. The material was characterized using transmission electron microscopy (TEM) and Fourier transform infrared/Raman (FT-IR/Raman) spectroscopy, and used for the first time in a flow injection on-line solid phase extraction (SPE) coupled with flame atomic absorption spectrometry (FAAS) to detect trace Cr (VI). Effective sorption of Cr (VI) was achieved at pH 2.0 with no interference from Cr (III) and other ions and 0.5 mol L⁻¹ NH₃·H₂O solution was found optimal for the complete elution of Cr (VI). An enrichment factor of 44 and was achieved under optimized experimental conditions at a sample loading of 2.0 mL min⁻¹ sample loading (300 s) and an elution flow rate of 2.0 mL min⁻¹ (24 s). The precision of the 11 replicate Cr (VI) measurements was 2.1% at the 100 μg L⁻¹ level with a detection limit of 0.2 μg L⁻¹ (3 s, n = 10) using the FAAS. The developed method was successfully applied to trace chromium determination in waste water. The accuracy was validated using a certified reference material of riverine water (GBW08607).     

Mixed-mode solid-phase extraction followed by acetylation and gas chromatography mass spectrometry for the reliable determination of trans-resveratrol in wine samples

This work presents an advantageous analytical procedure for the accurate determination of free trans-resveratrol in red and white wines. The proposed method involves solid-phase extraction (SPE), acetylation of the analyte in aqueous media and further determination by gas chromatography (GC) with mass spectrometry detection (MS). The use of a mixed-mode SPE sorbent provides an improvement in the selectivity of the extraction step; moreover, the presence of several intense ions in the electron impact mass spectra of its acetyl derivative guarantees the unambiguous identification of trans-resveratrol. Considering a sample intake of 10 mL, the method provides a limit of quantification (LOQ) of 0.8 ng mL⁻¹ and linear responses for concentrations up to 2.5 μg mL⁻¹, referred to wine samples. The average recovery, estimated with samples fortified at different concentrations in the above range, was 99.6% and the inter-day precision stayed below 8%. Trans-resveratrol levels in the analyzed wines varied from 3.4 to 1810 ng mL⁻¹. Cis-resveratrol was also found in all samples. In most cases, equal or higher responses were measured for this latter form than for the trans-isomer. The reduced form of resveratrol, dihydro-resveratrol, was systematically identified in red wines.     

Solid-phase microextraction on-fiber derivatization for the analysis of some polyphenols in wine and grapes using gas chromatography–mass spectrometry

The present study describes a new environmentally friendly sample pretreatment system based on solid-phase microextraction (SPME) for the sensitive determination of polyphenols. A derivatization process was necessary to convert the polar non-volatile compounds into volatile derivatives. Direct immersion (DI) SPME was used for the adsorption of polyphenols, and then the fiber was placed in the headspace of the derivatizing reagent, bis(trimethylsilyl)trifluoroacetamide (BSTFA). The separation was carried out by coupling gas chromatography with mass spectrometry in the selected ion monitoring mode, after silylation. Optimal extraction conditions were 25 °C for 10 min under continuous stirring using DI and a polyacrylate fiber. After extraction, the fiber was inserted into the headspace of BSTFA (10 μL) and the polyphenols were derivatized for 15 min at 50 °C. Desorption was carried out at 280 °C for 5 min. The method allowed the determination of both isomers cis- and trans-resveratrol, piceatannol, catechin and epicatechin in wine and grapes, and it was validated for linearity, detection and quantitation limits, selectivity, accuracy and precision. Detection limits ranged from 0.05 to 0.9 ng mL⁻¹ at a signal-to-noise ratio of 3, depending on the compound. Recoveries obtained for spiked samples were satisfactory for all compounds.     

The use of cyclic voltammetry for wine analysis: Determination of polyphenols and free sulfur dioxide

The use of cyclic voltammetry to characterize wines and wine polyphenols in a pH 3.3 model wine solution has been extended to take into account the effects of sulfur dioxide and polyphenol adsorption processes. A good correlation was obtained between a cyclic voltammetric measure, based upon the response produced before and after acetaldehyde additions, and the concentration of free sulfur dioxide in eight white wines (r² = 0.974). By the addition of acetaldehyde to the white wines, an important new step in the methodology, the area under the anodic scan in the potential range from −100 to 1200 mV (Ag/AgCl) closely matched the spectroscopic measure of total polyphenols (absorbance at 280 nm) for the white wines, when both were measured in terms of caffeic acid equivalents (r² = 0.949). The anodic peak area accounted for about 70% of the 280 nm total phenols measure, in catechin equivalents, for the red wines, and a good linear correlation was also obtained (r² = 0.942). The level of catechol and galloyl-containing polyphenols in the wines was calculated by measuring the size of the first anodic peak at around 450 mV after treatment of the wines with acetaldehyde; the peak current correlated well with the total caffeic acid derivatives in the white wines determined by HPLC (r² = 0.982). The concentration of flavonols was estimated by selective adsorption of these compounds onto the carbon electrode and determining the anodic peak current at 1120 mV, with good correlations obtained when compared to total flavonols as measured by HPLC (r² = 0.984 for the red wines, and r² = 0.987 for the white wines).     

Rapid determination of trans-resveratrol in red wine by solid-phase microextraction with on-fiber derivatization and multidimensional gas chromatography–mass spectrometry

There has been considerable public interest and a growing number of scientific studies linking certain phenolic compounds in grapes and wines, particularly trans-resveratrol (trans-3,5,4′-trihydroxystilbene, TRA), to human health benefits. Typical TRA concentrations in wine are very low. It is a polar compound with very low volatility, which makes it difficult to extract and to separate on a gas chromatography (GC) column without derivatization. In this study, a new method for trace analysis of TRA was developed using solid-phase microextraction (SPME) with on-fiber silylation derivatization. Multidimensional GC equipped with a heartcut valve and cryogenic focusing was coupled with a mass-selective detector and used for improved separations and analysis. The effects of SPME fiber selection, extraction time, temperature, and desorption time were investigated. The derivatization conditions, time/temperature and the volume of derivatization reagent were also optimized. The calibration curve was linear over the concentration range from 10 ng L⁻¹ to 5 mg L⁻¹, with a correlation coefficient of 0.9996. The average recovery of TRA in red wine was 83.6 ± 5.6%. The method detection limit (MDL) for TRA in ethanol:water (12.5:87.5, v/v) solution in this study was 7.08 ng L⁻¹ whereas the MDL for TRA in pure water was 2.85 ng L⁻¹. The new method was used to test the TRA content in six selected Iowa red wine samples. Measured concentrations varied from 12.72 to 851.9 μg L⁻¹.     

A comparison of solid-phase microextraction and stir bar sorptive extraction coupled to liquid chromatography for the rapid analysis of resveratrol isomers in wines, musts and fruit juices

A comparison of direct immersion solid-phase microextraction (DI-SPME) and stir bar sorptive extraction (SBSE) coupled to liquid chromatography (HPLC) with fluorimetric detection for the rapid analysis of resveratrol isomers is described. For DI-SPME, a polar Carbowax-template resin (CW/TPR) 50 μm fiber was the most efficient and optimum extraction conditions were 40 °C and an extraction time of 30 min, stirring in the presence of 5% (m/v) sodium chloride and 0.07 M acetate/acetic acid buffer (pH 6). Desorption was carried out using the static mode for 10 min. Linearity was obtained in the 5-150 and 2-150 ng mL⁻¹ ranges for trans- and cis-resveratrol, with detection limits of 2 and 0.5 ng mL⁻¹, respectively. When using SBSE, a polydimethylsiloxane (PDMS) twister provided best extraction by means of a derivatization reaction in the presence of acetic anhydride and potassium carbonate. The same time and temperature were used for the extraction step in the presence of 2.5% (m/v) sodium chloride, and liquid desorption was performed with 150 μL of a 50/50 (v/v) acetonitrile/1% (v/v) acetic acid solution in a desorption time of 15 min. Linearity was now between 0.5 and 50 ng mL⁻¹ for trans-resveratrol with a detection limit of 0.1 ng mL⁻¹, while cis-resveratrol could not be extracted. The proposed methods were successfully applied to determining the resveratrol isomer content of wine, must and fruit juices.     

Highly ordered Ti-SBA-15: Efficient H2 adsorbent and photocatalyst for eco-toxic dye degradation

Highly ordered 2D-hexagonal mesoporous titanium silicate Ti-SBA-15 materials (space group p6mm) have been synthesized hydrothermally in acidic medium employing amphiphilic tri-block copolymer, Pluronic F127 as structure directing agent. Samples are characterized by powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, FT IR spectroscopy, UV-visible diffuse reflectance measurements, N₂ adsorption/desorption and TG-DTA analysis. XRD and TEM results suggested the presence of highly ordered mesophase with hexagonal pore arrangements. BET surface area for Ti-SBA-15 (924 m² g⁻¹) is considerably higher than the pure silica SBA-15 (611 m² g⁻¹) prepared following the same synthetic route. UV-visible and FT-IR studies suggested the incorporation of mostly tetrahedral titanium (IV) species, along with some six-coordinated sites in the silicate network. This material shows very good H₂ adsorption capacity at higher pressure and excellent catalytic activity in the photocatalytic degradation of ecologically abundant dye methylene blue.     

Flow injection chemiluminescence determination of the total phenolics levels in plant-derived beverages using soluble manganese(IV)

This study established a flow injection (FI) methodology for the determination of the total phenolic content in plant-derived beverages based on soluble manganese(IV) chemiluminescence (CL) detection. It was found that mixing polyphenols with acidic soluble manganese(IV) in the presence of formaldehyde evoked chemiluminescence. Based on this finding, a new FI-CL method was developed for the estimation of the total content of phenolic compounds (expressed as milligrams of gallic acid equivalent per litre of drink) in a variety of wine, tea and fruit juice samples. The proposed method is sensitive with a detection limit of 0.02 ng mL⁻¹ (gallic acid), offers a wide linear dynamic range (0.5-400 ng mL⁻¹) and high sample throughput (247 samples h⁻¹). The relative standard deviation for 15 measurements was 3.8% for 2 ng mL⁻¹ and 0.45% for 10 ng mL⁻¹ of gallic acid. Analysis of 36 different samples showed that the results obtained by the proposed FI-CL method correlate highly with those obtained by spectrophotometric methods commonly used for the evaluation of the total phenolic/antioxidant level. However, the FI-CL method was found to be far simpler, more rapid and selective, with almost no interference from non-phenolic components of the samples examined.     

Hybrid sequential injection-flow injection manifold for the spectrophotometric determination of total sulfite in wines using o-phthalaldehyde and gas-diffusion

A new automated spectrophotometric method for the determination of total sulfite in white and red wines is reported. The assay is based on the reaction of o-phthalaldehyde (OPA) and ammonium chloride with the analyte in basic medium under SI conditions. Upon on-line alkalization with NaOH, a blue product is formed having an absorption maximum at 630 nm. The parameters affecting the reaction - temperature, pH, ionic strength, amount concentration and volume of OPA, amount concentration of ammonium chloride, flow rate and reaction coil length - and the gas-diffusion process - sample and HCl volumes, length of mixing coil, donor flow rate - were studied. The proposed method was validated in terms of linearity (1-40 mg L⁻¹, r = 0.9997), limit of detection (c_L = 0.3 mg L⁻¹) and quantitation (c_Q = 1.0 mg L⁻¹), precision (s_r = 2.2% at 20 mg L⁻¹ sulfite, n = 12) and selectivity. The applicability of the analytical procedure was evaluated by analyzing white and red wine samples, while the accuracy as expressed by recovery experiments ranged between 96% and 106%.     

Non-chromatographic determination of ultratraces of V(V) and V(IV) based on a double column solid phase extraction flow injection system coupled to electrothermal atomic absorption spectrometry

In this work, a non-chromatographic procedure for the on-line determination of ultratraces of V(V) and V(IV) is presented. The method involves a solid phase extraction-flow injection system coupled to electrothermal atomic absorption spectrometry (SPE-FI-ETAAS). The system holds two microcolumns (MC) set in parallel and filled with lab-made mesoporous silica functionalized with 3-aminopropyltriethoxy silane (APS) and mesoporous silica MCM-41, respectively. The pre-concentration of V(V) is performed by sorption onto the first MC (C1) filled with APS at pH 3, whilst that of V(IV) is performed by sorption onto the second column (C2) filled with mesoporous silica MCM-41 at pH 5. Aqueous samples containing both analytes are loaded and, after pre-concentration (pre-concentration factor PCF = 10, sorption flow rate = 1 mL min⁻¹, sorption time = 10 min), they are eluted in separate vessels with hydroxylammonium chloride (HC) 0.1 mol L⁻¹ in HCl 0.5 mol L⁻¹ (elution volume = 1 mL, elution flow rate = 0.5 mL min⁻¹). Afterwards, both analytes are determined through ETAAS with graphite furnace. Under optimized conditions, the main analytical figures of merit for V(V) and V(IV) are, respectively: detection limits (3 s): 0.5 and 0.6 μg L⁻¹, linear range: 2-100 μg L⁻¹ (both analytes), sensitivity: 0.015 and 0.013 μg⁻¹ L and sample throughput: 6 h⁻¹ (both analytes). Recoveries of both species were assayed in different water samples. Validation was performed through certified reference materials for ultratraces of total vanadium in river water.     

Optimization and validation of a method for the direct determination of catechin and epicatechin in red wines by HPLC/fluorescence

The present paper describes a direct procedure for the determination of catechin and epicatechin concentrations in red wines employing reverse-phase high performance liquid chromatography (RP HPLC) and detection by fluorescence. The method was performed using a sample volume of 10 µL without dilution. The separation process employed a Chromolith performance RP-18e (100 mm × 4.6 mm) column, and the mobile phase was composed of solvent A: methanol-acetic acid-water (90:8:2) and solvent B: water-acetic acid-methanol (10:2:88) at a flow rate of 1.0 mL min^− 1. Linearity was observed in the range of 1 to 30 mg L^− 1, with limits of detection and quantification of 0.27 and 0.89 mg L^− 1, respectively, for catechin and 0.33 and 1.01 mg L^− 1, respectively, for epicatechin. The precisions estimated by the relative standard deviation were 3.34 and 1.09% for catechin concentrations of 0.5 and 20 mg L^− 1 respectively and 2.82 and 0.49% for epicatechin concentrations of 0.5 and 20 mg L^− 1, respectively. The evaluation of the accuracy was done using an addition/recovery assay. Four wine samples were used, and the recoveries varied from 105 to 108% for catechin and from 97 to 119% for epicatechin. The method was applied to the analysis of red wine samples collected from the São Francisco region, Bahia State, Brazil. Nine samples were analyzed, and the catechin and epicatechin concentrations varied from 7.51 to 73.20 and from 5.08 to 43.32 mg L^− 1, respectively. The concentrations found agree with data reported in the literature.     

Hybrid mesoporous materials for on-line preconcentration of Cr(VI) followed by one-step scheme for elution and colorimetric determination at ultratrace levels

An hybrid mesoporous material synthesised in our laboratories for solid phase extraction (SPE) in flow through systems has been used for analytical purposes. The solid was obtained from mesoporous silica MCM-41 functionalized with 3-aminopropyltriethoxy silane by Sol-Gel methodology. In order to exploit the large sorption capacity of the material together with the possibility of modeling it for anions retention, a microcolumn (MC) filled with the solid was inserted in a flow system for preconcentration of Cr(VI) and its determination at ultratrace levels in natural waters. The analytical methodology involved a reverse flow injection system (rFI) holding a MC filled with the solid for the analyte extraction. Elution and colorimetric detection were carried out with 1-5 diphenylcarbazide (DPC) in sulfuric acid. DPC produced the reduction of Cr(VI) to Cr(III) together with the generation of a cationic red complex between Cr(III) and 1-5 diphenylcarbazone which was easily eluted and detected with a visible spectrophotometer. Moreover, the filling material got ready for the next sample loading remaining unspoiled for more than 300 cycles.The effect of several variables on the analytical signal as well as the influence of cationic and anionic interferences were discussed. Particular attention was given to sulfuric acid interference since it is the required media for the complex generation.Under optimal conditions, 99.8% of Cr(VI) recovery was obtained for a preconcentration time of 120 s (sample and DPC flow rates = 1 mL min⁻¹) and an elution volume of 250 μL. The limit of detection (3 s) was found to be 0.09 μg L⁻¹ Cr(VI) with a relative standard deviation (n = 10, 3 μg L⁻¹) of 1.8.Since no Cr(III) was retained by the solid material and Cr(VI) was completely adsorbed, electrothermal atomic absorption spectrometry (ET AAS) determinations of Cr(III) were also performed by simply measuring its concentration at the end of the microcolumn after Cr(VI) retention by the mesoporous solid.Applications to the determination of Cr(VI) and Cr(III) in natural waters and the validation of the methodology were also studied.     

Determination of 4-ethylcatechol in wine by high-performance liquid chromatography-coulometric electrochemical array detection

A HPLC method using a coulometric electrode array detector (CEAD) to analyse 4-ethylcatechol in wine was established. The procedure does not require any sample preparation or analyte derivatisation and performs chromatographic separation in a short time. The assay method is linear up to 1520 μg L⁻¹ and precise (R.S.D. < 3%), with limits of detection and quantitation of 1.34 μg L⁻¹ and 2.2 μg L⁻¹, respectively. Recoveries in spiked wine samples ranged from 95% to 104% with a median value of 102% and matrix effects were not observed. The method was applied to the evaluation of the concentration of 4-EC in 250 commercial Italian wines. The red wines analysed had median, 75° percentile and maximum values of 37 μg L⁻¹, 89 μg L⁻¹ and 1610 μg L⁻¹, respectively. For Sangiovese-based wines the mean ratios of 4-EP and 4-EG to 4-EC were 3.7:1 and 0.7:1, respectively. The feasibility of a cheaper fluorimetric approach to 4-EC quantification was investigated.     

The antioxidant activity of wines determined by the ABTS(+) method: influence of sample dilution and time

The free radical scavenging activity of 42 Spanish commercial wines was determined using the 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS⁺). The ABTS⁺ radical was generated enzymatically using a horseradish peroxidase and hydrogen peroxide. The presence of wine phenolic compounds caused the absorbance of the radical to decay at 414 nm. The measurement conditions were optimised. The total phenolic content of wines ranged from 1262 to 2389 mg l⁻¹ for red wines and 70 to 407 mg l⁻¹ for white wines, expressed as gallic acid equivalents. The phenolic content of Sherry wines was similar to that of white wines. Optimum dilutions for white and Sherry wines were set up as a function of their total phenolic content (for total phenol index, TPI<300 mg gallic acid per liter, dilution 2.5:10 to 5:10; for TPI>300 mg gallic acid per liter, dilution 1:10 to 3:10). Red wines absorb at the wavelength of measurement and dilutions between 0.35:10 and 0.1:10 are advisable. Reaction kinetics were also monitored and the antioxidant activity, expressed as Trolox Equivalent Antioxidant Capacity (TEAC), was determined at 2 and 15 min of reaction. The mean values for TEAC_2 min were 5.01±1.40 mM for red wines, 0.46±0.32 mM for white wines and 0.26±0.19 mM for Sherry wines. At 15 min, mean values were 6.93±2.41 mM for red wines, 0.67±0.47 mM for white wines and 0.26±0.19 mM for Sherry wines. The correlation coefficients were better at 2 min (r=0.9012) than at 15 min (r=0.8462) when compared with TPI. Hence, TEAC_2 min seems to be a more appropriate measure.     

Trace level determination of cadmium in wine by on-line preconcentration in a 5-Br-PADAP functionalized wool-packed microcolumn coupled to flame atomic absorption spectrometry

An on-line retention and preconcentration system based on a sheep wool-packed microcolumn combined with flame atomic absorption spectrometry is proposed for trace level determination of Cd in wine. A chelating reagent 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol was immobilized onto the wool before retention of the analyte. Several factors influencing the preconcentration efficiency of Cd and his subsequent determination, such as pH, eluent type, sample and eluent flow rates, interfering effects, were studied. A preconcentration factor of 39 was obtained with only 20 mL of sample. The relative standard deviation for five determinations of 1 μg L⁻¹ Cd was 3.4%. The calibration graph was linear with a correlation coefficient of 0.998 at levels near the detection limit and up to at least 25 μg L⁻¹. The limit of detection was 37 ng L⁻¹. The accuracy of the proposed methodology was tested by comparison of the results with those obtained by electrothermal atomic absorption spectrometry analysis along with a recovery study. Finally, the method was employed for evaluating Cd levels in different wines including, blank, rose, and red.     

Determination of azoxystrobin residues in grapes, musts and wines with a multicommuted flow-through optosensor implemented with photochemically induced fluorescence

In this paper, the conversion of azoxystrobin in a strongly fluorescent degradation product by UV irradiation with quantitative purposes and its fluorimetric determination are reported for the first time. A multicommuted flow injection-solid phase spectroscopy (FI-SPS) system combined with photochemically-induced fluorescence (PIF) is developed for the determination of azoxystrobin in grapes, must and wine. Grape samples were homogenized and extracted with methanol and further cleaned-up by solid-phase extraction on C₁₈ silica gel. Wine samples were solid-phase extracted on C₁₈ sorbent using dichloromethane as eluent. Recoveries of azoxystrobin from spiked grapes (0.5-2.0 mg Kg⁻¹), must (0.5-2.0 μg mL⁻¹) and wine (0.5-2.0 μg mL⁻¹) were 84.0-87.6%, 95.5-105.9% and 88.5-111.2%, respectively. The quantification limit for grapes was 0.021 mg Kg⁻¹, being within European Union regulations, and 18 μg L⁻¹ and 8 μg L⁻¹ for must and wine, respectively.