Optimized determination of iron in grape juice, wines, and other alcoholic beverages by atomic absorption spectrometry

This paper describes a study of the different methods of sample preparation for the determination of iron in grape juice, wines, and other alcoholic beverages by atomic absorption spectrometry with electrothermal atomization; results are also reported for the practical application of these methods to the analysis of commercial samples produced in Spain. The methods examined include dealcoholization and dry and wet mineralization treatment using different acids and/or mixtures of them, both with and without heating. The sensitivity, detection limit, accuracy, precision, and selectivity of each method were established. The best results were obtained for wet mineralization with heated acid (HNO3-H2SO4); the results for table wines had an accuracy of 97.5-101.6%, a relative standard deviation of 3.51%, a detection limit of 19.2 micrograms/L, and a determination limit of 32.0 micrograms/L. The method was also sufficiently sensitive and selective. It was applied to the determination of iron in grape juice, different types of wines, and beverages with high alcoholic content, all of which are produced and widely consumed in Spain. The values obtained ranged from 3.394 +/- 2.15 mg/L for the juice, 2.938 +/- 1.47 mg/L for the white wines, 19.470 +/- 5.43 mg/L for the sweet wines, 0.311 +/- 0.07 mg/L for the brandies, and 0.564 +/- 0.12 mg/L for the anisettes. Thus, the method is useful for routine analysis in the quality control of these beverages.     

Validation of methodology for simultaneous determination of synthetic dyes in alcoholic beverages by capillary electrophoresis

In this work a method of analysis for synthetic dyes was developed using capillary electrophoresis in alcoholic beverages. The analyses were carried out with fused silica capillary, with 73 cm effective length, at 35 degrees C, buffer phosphate solution of 10 mmol/L with sodium dodecyl sulphate 10 mmol/L, pH 11, and +25 kV of voltage. For dye analyses, three wavelengths in the visible region were used for the qualitative and quantitative determination of the 11 synthetic dyes allowed in Brazil: 450, 525 and 625 nm for the yellow, red and blue dyes, respectively. The detection limits varied from 0.4 to 2.5 microg/mL and the quantification limits varied from 1.3 to 7.1 microg/mL. The average recovery was 92.6 and 104.0% at two levels of concentration. Repeatability for standards and spiked sample showed that the calculated values were greater than the observed values, demonstrating the precision of the method. The proposed and validated method was used to analyze some alcoholic beverage samples, consisting of 12 red wines, 9 coolers, 6 aromatized spirits, 7 bitters, 3 cocktails and 8 liquors from different Brazilian manufacturers. The results showed the coolers, bitters and red wines did not have synthetic dyes, but dyes were found in six of the eight analyzed liquor samples. In all the samples of cocktails and spirits, the presences of dyes were observed. No analyzed sample exceeded the limit established by Brazilian legislation (maximum 30 mg/100 mL).     

Determination of glutathione content in grape juice and wine by high-performance liquid chromatography with fluorescence detection

A modified preparation of sample was developed for the determination of glutathione content in grape juice and wine by high-performance liquid chromatography with fluorescence detection, using on-line pre-column derivatization. Ice-cold deoxygenated methanol was used to deactivate the oxidation enzymes in juices or wines and keep the glutathione stable. The optimum recovery of glutathione content in grape juice and wine was obtained when either the sample of grape juice or wine was mixed in ice-cold deoxygenated methanol in the ratio 10:90 (v:v) and further diluted in sodium acetate buffer in the ratio 1:1 (v:v). The optimized method was validated for linearity, limit of detection, limit of quantification, precision and uncertainty. According to the validation data the method is appropriate for the determination of glutathione content in grape juice and wine. Glutathione contents in grape juices made from White Muscat grapes and Sauvignon Blanc wines were analysed. The average glutathione content in 28 young Sauvignon Blanc wines was 12.5 mg L⁻¹.     

Comparison of extraction techniques for gas chromatographic determination of volatile carbonyl compounds in alcohols

Two extraction procedures, i.e. conventional liquid-liquid extraction (LLE) and liquid solid-phase microextraction (SPME) for extraction of the oximes formed after derivatization of carbonyl compounds with o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) in alcoholic solutions have been compared. The limit of detection for LLE followed by GC-ECD determination of C1-C6 was in the range of 0.23-3.3 microg/L, whereas for liquid SPME 0.005-0.33 microg/L. Both methods elaborated can be applied to the determination of carbonyl compounds present in spirits and alcoholic beverages.     

Comparison of volatile constituents extracted from model grape juice and model wine by stir bar sorptive extraction-gas chromatography-mass spectrometry

A stir bar sorptive extraction (SBSE) method coupled with gas chromatography-mass spectrometry was optimised for the analysis of volatile components of a model wine, based on a previously optimised method used for analysis of the same components in model grape juice. The presence of ethanol in the model wine sample matrix resulted in decreased sensitivity of the method toward most of the volatile constituents. Mean percent relative recoveries and reproducibilities (%CV) were 22.8% and 7.1%, respectively, compared with 28.4% and 8.5% for model grape juice. The mean limit of detection (LoD) ratio (juice:wine) was 0.25. Similar sensitivities for the two sample matrices using this method were achieved by changing the split ratio from 20:1 (grape juice) to 5:1 (wine), giving a mean limit of detection ratio (juice:wine) of 1.0, thus allowing direct comparison of chromatograms of volatile components in the two matrices. This enabled direct comparisons of grape juices and the wines derived from them by alcoholic yeast fermentation. The influence of ethanol concentration in the range 9-15% on method sensitivity is discussed, using an overlay of the total ion chromatograms. The use of a gas saver device for the 5:1 split ratio analysis of desorbed model wine aroma compounds is discussed in terms of preventing extraneous reaction of sorbent and stationary phases with air during analysis.     

Contactless conductivity detection of sodium monofluoroacetate in fruit juices on a CE microchip

Rapid and quantitative determination of sodium monofluoroacetate in diluted fruit juices (dilution 1:9 v/v in deionized water) and tap water was performed by microchip CE, using contactless conductivity detection. A separation buffer consisting of 20 mM citric acid and histidine at pH 3.5 enabled the detection of the monofluoroacetate (MFA) anion in diluted apple juice, cranberry juice, and orange juice without lengthy sample pretreatments. The analyte was very well separated from interfering anionic species present in juices and tap water. LODs in diluted juices and tap water were determined to be 125, 167, 138, and 173 microg/L for tap water, apple juice, cranberry juice, and orange juice, respectively, based upon an S/N of 3:1. Taking into account the dilution factor, the LODs for juice samples range from 1 to 2 mg/L, which is adequate for monitoring the toxicity of MFA in these juice beverages and tap water. The calibration curves for MFA in diluted fruit juices were linear over the range of 500 microg/L to 80 mg/L. The total analysis time for detecting the MFA anion in fruit juices was less than 5 min, which represents a considerable reduction in analysis time compared to other analytical methods currently used in food analysis.     

超高效液相色谱-串联四极杆质谱法测定葡萄中单咖啡酰酒石酸酯、单香豆酰酒石酸酯和单阿魏酰酒石酸酯

建立了超高效液相色谱-串联四极杆质谱测定葡萄汁、皮和籽中羟基桂皮酒石酰酯类化合物含量的方法。采用的色谱柱为Waters UPLC HSS T3 (150 mm×2.1 mm, 1.7 μm),流动相为含0.1%甲酸的水-乙腈体系,梯度洗脱,流速0.3 mL/min,柱温35 ℃;质谱采用电喷雾离子源、负离子多反应检测模式。对单香豆酰酒石酸酯和单阿魏酰酒石酸酯,其含量以单咖啡酰酒石酸酯当量表示。结果表明,单咖啡酰酒石酸酯在25～2000 μg/L范围内线性关系良好(r2=0.9989);检出限为0.25 μg/L,定量限为25 μg/L;在250、750、1200 μg/L添加水平下单咖啡酰酒石酸酯的平均回收率为97.7%～99.5%,相对标准偏差小于2.5%。实验结果表明,葡萄汁、皮和籽中羟基桂皮酒石酰酯类化合物的含量差异显著。该方法简单快速、灵敏度高、回收率高、准确性好,可用于葡萄产品中单咖啡酰酒石酸酯、单香豆酰酒石酸酯和单阿魏酰酒石酸酯的分析。     

Determination of metolcarb and diethofencarb in apples and apple juice by solid-phase microextraction-high performance liquid chromatography

A method for the determination of metolcarb and diethofencarb in apples and apple juice is developed using solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC). The experimental conditions of SPME, such as the kind of extraction fiber, extraction time, stirring rate, pH of the extracting solution, and desorption conditions are optimized. The SPME is performed on a 60 microm polydimethylsiloxane/divinylbenzene fiber for 40 min at room temperature with the solution being stirred at 1100 rpm. The extracted pesticides on the SPME fiber are desorbed in the mobile phase into SPME-HPLC interface for HPLC analysis. Separations are carried out on a Baseline C18 column (4.6 i.d. x 250 mm, 5.0 microm) with acetonitrile-water (55/45, v/v) as the mobile phase at a flow rate of 1.0 mL/min, and photodiode-array detection at 210 nm. For apple samples, the method is linear for both metolcarb and diethofencarb in the range of 0.05-1.0 mg/kg (r > 0.99), with a detection limit (S/N = 3 ) of 15 and 5 microg/kg, respectively. For apple juice, the method is linear for both metholcarb and diethofencarb over the range of 0.05-1.0 mg/L (r > 0.99) with the detection limit (S/N = 3 ) of 15 and 3 microg/L, respectively. Excellent recovery and reproducibility values are achieved. The proposed method is shown to be simple, sensitive, and organic solvent-free, and is suitable for the determination of the two pesticides in apples and apple juice.     

Evaluation of headspace solid-phase microextraction for the analysis of volatile carbonyl compounds in spirits and alcoholic beverages

A method was developed for the determination of C1-C6 carbonyl compounds in alcoholic solutions using pentafluorobenzoxymation followed by headspace sampling solid-phase microextraction and subsequent analysis by GC with electron-capture detection. Experimental conditions-alcohol content, exposure time, temperature and sample agitation were optimised. In this method, a spirit or distilled alcoholic beverage is first adjusted to 20% (v/v) alcohol. Detection limits for particular aldehydes and ketone varied from 0.05 to 0.5 microg/l and relative standard deviation was between 2.3 and 20%. Generally, the method showed good linearity for the tested concentration range 8 microg/l-0.32 mg/l with regression coefficients ranging between 0.9434 and 0.9983. The method was applied to the analysis of real alcoholic beverages (vodkas).     

Method Development and Validation for the Determination of Five Synthetic Food Colorants in Alcoholic Beverages by Reversed‐Phase High Performance Liquid Chromatography Coupled with Diode‐Array Detector

Abstract

An accurate method based on the use of reversed‐phase high performance liquid chromatography coupled with diode‐array detection was devised for the determination of five synthetic food colorants added to alcoholic beverages with natural colors. A C18 stationary phase was used and the mobile phase contained methanol and 40 mM ammonium acetate buffer solution. The synthetic food colorants were detected at their corresponding individual characteristic maxima of absorbance wavelength. Successful separation was achieved within 11 min for all the analytes using an optimized gradient elution, column temperature, buffer concentration and flow rate. Accurate sample quantification was feasible using matrix‐matched calibration curves. The method was successfully validated by determination of linearity ranges, the limits of quantification and detection, precision and recovery for all colorants tested. The proposed and validated method was used to analyze some alcoholic beverage samples, consisting of eight red wines, six coolers, four aromatized spirits, five bitters, three cocktails and four liquors from different Chinese manufacturers. The results showed the bitters and red wines did not have synthetic colorants, but colorants were found in all the samples of other kinds of alcoholic beverages. No analyzed sample exceeded the limit established by Chinese legislation.     

Determination of ethyl carbamate in alcoholic beverages: an interlaboratory study to compare HPLC-FLD with GC-MS methods

An international interlaboratory study on the determination of ethyl carbamate in alcoholic beverages by a new HPLC-FLD and by the official GC-MS methods is presented. The aim of this study was to improve the knowledge about precision and accuracy parameters of the new method and to compare the performance of both HPLC and GC methods. Five different samples representing table wines, fortified wines (red and white), distilled spirits, and wine spirits were available for analysis by each participant. Despite the low number of participants (6), the results obtained by the laboratories using the HPLC-FLD method are comparable to those obtained by GC-MS methods. The present study emphasizes the possibility to use, as routine, a much simpler analytical method than the current reference method by GC-MS for ethyl carbamate determination in alcoholic beverages.     

Multiple headspace solid-phase microextraction of ethyl carbamate from different alcoholic beverages employing drying agent based matrix modification

Multiple headspace solid-phase microextraction (MHS-SPME) combined with gas chromatography-nitrogen phosphorus detector is proposed to determine the toxic contaminant ethyl carbamate (EC) in various alcoholic beverages after matrix modification. The remarkable feature of this method is that matrix effect, which commonly appears in SPME-based analysis, is avoided by determining the total amount of the analyte in the sample. To increase the sensitivity of the method, a novel polyethylene glycol/hydroxy-terminated silicone oil fiber was developed by sol-gel technique and applied for the analysis. Owing to the high polarity and hydrophilia of EC, an important problem still remains because the adsorption by sample matrix causes low transport of EC to the headspace and thus invalidates MHS-SPME for quantification. Mixing with anhydrous sodium sulphate, the sensitivity of the method can be improved. A Taguchi's L(16) (4(5)) orthogonal array design was employed to evaluate potentially significant factors and screen the optimum conditions for MHS-SPME of EC. Under the optimized conditions, limit of detection of 0.034 mg L(-1) was obtained. Relative standard deviation of replicate samples (n=6) was 2.19%. The proposed method was linear in the range of 0.04-100 mg L(-1), and the coefficient of determination was 0.9997. The method was used to determine EC in various alcoholic beverages. The concentrations obtained were compared with those obtained by standard addition method and no statistically significant differences were observed.     

Coacervative extraction of Ochratoxin A in wines prior to liquid chromatography/fluorescence determination

Coacervates made up of reverse micelles of decanoic acid were assessed as a new strategy for the simplification of wine sample treatment in the determination of Ochratoxin A (OTA). Simultaneous extraction/concentration of this contaminant was based on both hydrophobic and hydrogen bond OTA:coacervate interactions. Parameters affecting extraction efficiency and concentration factors were studied. Concentrations of decanoic acid and tetrahydrofuran (THF) were the most influential parameters, being 0.5% of acid and 5% of THF the selected ones. The procedure was very robust, so that the extractions were not influenced by the pH and the nature or concentration of matrix components. OTA recoveries from different types of wines (white, rosé and red) ranged between 85 and 100% and the actual concentration factors varied from 105 to 125 for sample volumes of 15 mL. The detection limits for OTA, after liquid chromatography/fluorimetry (LC/FL) analysis of the coacervate (20 microL), were 4.5 ng L(-1) in white and rosé wines and 15 ng L(-1) in red wines, values which were far below the threshold limit established for OTA by EU directives (2.0 microg L(-1)). No clean-up of the extracts was required for any of the samples analysed. The overall sample treatment took about 15-20 min and several samples could be simultaneously treated using conventional lab equipment. The precision of the method, expressed as relative standard deviation, was about 5%. The approach developed was successfully applied to the determination of OTA in different wine samples from the South of Spain. The concentrations found ranged between 0.015 and 0.091 microg L(-1).     

Derivatization, identification and separation of carboxylic acids in wines and beverages by high-performance liquid chromatography

A high-performance liquid chromatographic method for the derivatization, identification and separation of carboxylic acids in beverages such as wines and other commercial drinks or natural fruit juices has been developed. The accuracy and precision of the method are discussed with reference to specific methods for the determination of single acids. Applications to the analysis of different wines and beverages are demonstrated.     

高效液相色谱法测定柑橘汁中的柠檬苦素和柚皮苷

柑橘汁的苦味主要是由于柚皮苷和柠檬苦素的存在所致,其含量的测定可用于控制柑橘类果汁的质量。采用高效液相色谱法在KR100-5C18(4.6 mm i.d.×250 mm,5 μm)上,分别以乙腈-四氢呋喃-水(体积比为17.5∶17.5∶65)和甲醇-冰醋酸-水(体积比为40∶1∶59)为流动相（流速均为1 mL/min）,在207 nm和283 nm检测波长下分别测定了柠檬苦素和柚皮苷。实验结果表明,柠檬苦素在1.00～50.00 mg/L时线性关系良好(r=0.9992),检出限为0.07 μg,平均加标回收率为98.69%,相对标准偏差（RSD）为2.5%;柚皮苷在20.00～160.00 mg/L时线性关系良好(r=0.9988),检出限为0.14 μg,平均加标回收率为100.13%,RSD为1.5%。用该法检测柑橘汁样品中的柠檬苦素与柚皮苷,方法简便、快速、准确。     

Determination of bisphenol A in sewage effluent and sludge by solid-phase and supercritical fluid extraction and gas chromatography/mass spectrometry

Methods have been developed for the determination of bisphenol A (BPA) residues in municipal sewage and sludge samples. BPA in wastewater samples was enriched with a C18 solid-phase extraction cartridge, eluted with acetone, and converted to the pentafluoropropionyl derivative. For sludge samples, BPA was acetylated and extracted with supercritical carbon dioxide. In both cases, BPA-d16 was used as a surrogate to monitor extraction efficiency. Final analyses of derivatized sample extracts were performed by gas chromatography/mass spectrometry operating in the electron impact mode. For water samples, mean recoveries and standard deviations were 89 +/- 6, 94 +/- 4, and 85 +/- 7% at fortification levels of 1, 0.1, and 0.025 microg/L, respectively, with a method detection limit of 0.006 microg/L. For solid waste samples, mean recoveries and standard deviations were 93 +/- 5 and 92 +/- 6% at fortification levels of 2.5 and 0.25 microg/g, respectively, and the method detection limit was 0.05 microg/g. For the Canadian samples under investigation, concentrations of BPA ranged from 49.9 to 0.031 microg/L in sewage influent and effluent, and from 36.7 to 0.104 microg/g in sludge.     

毛细管气相色谱法快速测定西瓜及饮料中的甜蜜素

建立了毛细管气相色谱法测定西瓜和饮料中甜蜜素的方法.甜蜜素在0.1-10.0g/L范围内线性关系良好,相关系数R2= 0.999 2.以10倍信噪比计算,方法的定量限为0.5 mg/kg.两种果味饮料样品测定结果的相对标准偏差分别为0.87%,1.03%(n=6),西瓜样品的加标回收率为96.0%-103.8%,饮料样...     

Comparison of extraction techniques for gas chromatographic determination of volatile carbonyl compounds in alcohols

Two extraction procedures, i.e. conventional liquid-liquid extraction (LLE) and liquid solid-phase microextraction (SPME) for extraction of the oximes formed after derivatization of carbonyl compounds with o-(2,3, 4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) in alcoholic solutions have been compared. The limit of detection for LLE followed by GC-ECD determination of C₁–C₆ was in the range of 0.23–3.3 μg/L, whereas for liquid SPME 0.005–0.33 μg/L. Both methods elaborated can be applied to the determination of carbonyl compounds present in spirits and alcoholic beverages. Received: 26 September 2000 / Revised: 14 January 2001 / Accepted: 16 January 2001     

毛细管离子色谱法测定酒和饮料中阳离子

建立了毛细管离子色谱测定酒、饮料等样品中阳离子的分析方法。使用毛细管离子色谱柱IonPac CS12A(250 mm×0.4 mm, 8 μm),以甲基磺酸淋洗液发生器(EGC-MSA)产生18 mmol/L的甲基磺酸为流动相,进样量0.4 μL,在流速0.01 mL/min的条件下,采用自循环抑制电导检测的方法对啤酒、葡萄酒、白酒、果汁及奶茶等样品中的阳离子含量进行检测。结果表明,毛细管离子色谱法能满足阳离子含量的测定要求,系统稳定不易堵,在灵敏度方面优于常规离子色谱系统。该方法能够快速、准确地测定酒、饮料等样品中的5种阳离子(钠、铵、钾、镁和钙),回归方程的相关系数在0.9997以上,实际样品的加标回收率为95.2%～103.3%。该方法具有灵敏度高,操作简单,环境友好的特点。     

Identification and Quantitation of Hydroxytyrosol in Italian Wines

Hydroxytyrosol (HTy) is a potent natural antioxidant found in olive oil and in mill waste waters. Although wines are rich in polyphenols, hydroxytyrosol has not been identified in wines so far. We have analyzed ten wines from different grape varieties grown in several Italian regions, using a gas-chromatograph coupled to a mass selective detector (GC-MS). Solid-phase extraction of wine samples was performed on a C18 column, with ethyl acetate used as eluting agent. Eluates were derivatized with bis(trimethylsilyl)trifluoroacetamide (BSTFA) and analyzed by GC-MS using one target and two qualifying ions. The detection limit was 15 pg/μL, with 49% average recovery. Under these experimental conditions hydroxytyrosol was detected in all wines analyzed. Its average concentrations in red and white wines were 4.0 mg/L and 1.9 mg/L, respectively.