Relationship between sensory and instrumental analysis of 2,4,6-trichloroanisole in wine and cork stoppers

The effect of different corks stoppers on the sensory and instrumental determination of 2,4,6-trichloroanisole (TCA) was studied in wine and cork. A relationship between both measurements was also established.Four types of cork were used to seal white wine bottles for 8 months. The stoppers were from different raw material: a high quality commercial batch (C), slabs with yellow stain (YS) and slabs with a high musty and mouldy taint (T). Spiked samples (S) were prepared from C batch by injecting 1002 ng of TCA into the cork stoppers.TCA was determined by gas chromatography with electron capture detection after headspace solid phase microextraction in bottled wine (12 per group) and after extraction with pentane in the case of corks (six per group). Seven semi-trained assessors evaluated the different samples using a ranking test in 12 and six sessions for wine and cork stoppers, respectively.Wines and corks from S samples showed the highest TCA values in both sensory and instrumental measurements, the lowest values being for C samples. YS and T corks had intermediate values, although in general TCA concentration was higher in T. A slight tendency to increase the TCA content in stoppers with yellow stain compared to C samples was observed in wine. A high correlation coefficient (r=0.82) was found between sensory and instrumental analysis for wine, whereas this coefficient was much lower (r=0.56) for cork stoppers. Some hypotheses are given in order to explain these differences.     

Optimisation of a microwave-assisted extraction method for the simultaneous determination of haloanisoles and halophenols in cork stoppers

This study presents a method based on the use of microwave-assisted extraction (MAE) for the quantitative analysis of 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA), pentachloroanisole (PCA), 2,4,6-tribromoanisole (TBA), 2,4,6-trichlorophenol (TCP), 2,3,4,6-tetrachlorophenol (TeCP), pentachlorophenol (PCP) and 2,4,6-tribromophenol (TBP) in cork stoppers. The influential parameters of the MAE procedure (extraction time, temperature and solvent volume) were optimised using a central composite experimental design combined with desirability functions. The optimal conditions identified were temperature 170 degrees C, solvent volume 35 mL and extraction time 90 min. MAE extracts were concentrated and derivatised prior to separation and quantification by gas chromatography with electron capture detection. To evaluate the applicability of the proposed MAE method, recovery results were compared with those obtained with the Soxhlet extraction method; the results were similar with both extraction methods. The new method was also satisfactorily applied to real cork stopper samples.     

Purge-and-trap preconcentration system coupled to capillary gas chromatography with atomic emission detection for 2,4,6-trichloroanisole determination in cork stoppers and wines

A method based on solvent extraction and purge-and-trap capillary gas chromatography with atomic emission detection (PT-GC-AED) for the determination of 2,4,6-trichloroanisole (TCA) in wines and cork stoppers was optimized and evaluated. TCA was previously extracted from the samples in pentane and the preconcentrated extract was reconstituted in water before being injected into the chromatograph by means of the PT system. Element-specific detection and quantification was carried out by monitoring the chlorine (479 nm) emission line. Two different calibration graphs were used to quantify TCA in the cork or the wine samples, owing to the interference produced by the ethanol content in the wines. Detection limits of 25 pg g(-1) and 5 ng l(-1) were obtained for corks and wines, respectively. The method provided recoveries from spiked samples ranging from 88.5 to 102.3%, confirming the reliability of the procedure and its suitability for routine monitoring.     

Determination of odour-causing volatile organic compounds in cork stoppers by multiple headspace solid-phase microextraction

Multiple headspace solid-phase microextraction (MHS-SPME) coupled with gas chromatography-mass spectrometry has been applied in order to determine 2,4,6-trichloroanisole (2,4,6-TCA), guaiacol, 1-octen-3-ol and 1-octen-3-one in three samples of cork stoppers. These compounds are responsible for cork taint in wine and can modify the organoleptic properties of bottled wine. Variables such as temperature, addition of water, extraction time, and amount of cork were studied. The extractions were performed with a 50/30 microm divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fibre for 45 min at 100 degrees C using 20 mg of cork. For calibration, 50 microL of VOC aqueous solutions were used and the extraction were carried out for 45 min at 75 degrees C. The limits of detection of the method expressed as ng of VOC per g of cork were 0.3 for 2,4,6-TCA, 7.5 for guaiacol, 1.7 for 1-octen-3-one and 1.9 for 1-octen-3-ol. Relative standard deviation of replicate samples was less than 10%. Significant losses of analytes were observed when the samples were ground at room temperature. Finally, a recovery study was performed and the MHS-SPME results were validated using Soxhlet extraction results.     

Determination of 2,4,6-trichloroanisole and 2,4,6-tribromoanisole on ng L-1 to pgL-1 levels in wine by solid-phase microextraction and gas chromatography-high-resolution mass spectrometry

A gas chromatography-high-resolution mass spectrometry (GC-HRMS) method using solid-phase microextraction (SPME) for the determination of 2,4,6-trichloroanisole (TCA) and 2,4,6-tribromoanisole (TBA) in wine at low ng L(-1) levels was developed. A robust SPME method was developed by optimizing several different parameters, including type of fiber, salt addition, sample volume, extraction and desorption time. The quantification limit for TCA and TBA in wine was lowered substantially using GC-HRMS in combination with the optimized SPME method and allowed the detection of low analyte concentrations (ng L(-1)) with good accuracy. Limits of quantification for red wine of 0.3 ng L(-1) for TCA and 0.2 ng L(-1) for TBA with gas chromatography-negative chemical ionization mass spectrometry and 0.03 ng L(-1) for TCA and TBA were achieved using GC-HRMS. The method was applied to 30 wines of which 4 wines were sensorically qualified as cork defected. TCA was found in three of these wines with concentrations in the range 2-25 ng L(-1). TBA was not detected in any of the samples.     

气相色谱-质谱法测定软木塞中2种霉味物质

建立了一种简便、快速的可同时测定软木塞中两种霉味物质(2,4,6-三氯苯甲醚(TCA)和2,4,6-三溴苯甲醚(TBA))的气相色谱-质谱联用(GC-MS)方法。软木塞样品采用甲醇超声萃取,N-丙基乙二胺(PSA)固相萃取柱净化,浓缩后采用GC-MS进行分析,外标法定量。在10～10000 μg/L的质量浓度范围内,TCA和TBA均有较好的线性关系,相关系数(r2)大于0.99。通过对不同种类的软木塞空白样品进行加标回收率试验和精密度试验考察方法的可行性。结果表明TCA和TBA的回收率介于88.4%与97.6%之间,相对标准偏差介于1.02%与4.58%之间。TCA和TBA的检出限分别为12 μg/L和18 μg/L,定量限分别为40 μg/L和50 μg/L。本方法适用于市售瓶装葡萄酒软木塞中TCA和TBA的检测。     

Application of robust NiTi-ZrO2-PEG SPME fiber in the determination of haloanisoles in cork stopper samples

In this study, a novel solid-phase microextraction (SPME) fiber obtained using sol-gel technology was applied in the determination of off-flavor compounds (2,4,6-trichloroanisole (TCA), 2,4,6-tribromoanisole (TBA) and pentachloroanisole (PCA)) present in cork stopper samples. A NiTi alloy previously electrodeposited with zirconium oxide was used as the substrate for a poly(ethylene glycol) (PEG) coating. Scanning electronic microscopy showed good uniformity of the coating and allowed the coating thickness to be estimated as around 17 micarom. The optimization of the main parameters influencing the extraction efficiency, such as cork sample mass, sodium chloride mass, extraction temperature and extraction time were optimized using a full factorial design, followed by a Doehlert design. The optimum conditions were: 20 min of extraction at 70 degrees C using 60 mg of the cork sample and 10 mL of water saturated with sodium chloride in a 20 mL amber vial with constant magnetic stirring. Satisfactory detection limits between 2.5 and 5.1 ng g(-1) were obtained, as well as good precision (R.S.D. in the range of 5.8-12.0%). Recovery tests were performed on three different cork samples, and values between 83 and 119% were obtained. The proposed SPME fiber was compared with commercially available fibers and good results were achieved, demonstrating its applicability.     

Evaluation of an extraction method in the determination of the 2,4,6-trichloroanisole content of tainted cork

A method based on solvent extraction and GC-electron-capture detection analysis for the determination of 2,4,6-trichloroanisole (TCA) from cork has been evaluated and optimised. Our sample treatment consists of an extraction stage with pentane while the sample and solvent are kept in contact in a mechanical shaker (shake-flask extraction). Different extraction conditions have been tested in order to find the best compromise between efficiency and time of analysis. Different columns were evaluated for use in the concentration and purification step. A silica column was found to give the best performance in terms of recovery of TCA and repeatability. Pentane and mixtures of pentane-diethyl ether at different ratios were tested as eluting agents. It was found that 10 ml pentane allowed the recovery of retained TCA. Finally, the eluate was concentrated and injected into the chromatograph for TCA determination. The optimised chromatographic conditions enabled the quantification of TCA and 2,6-dichloroanisole, which was assayed as the internal standard. The shake-flask extraction method was compared with Soxhlet and ultrasound assisted extraction procedures using pentane as a solvent. Similar results were obtained for the shake-flask and Soxhlet extraction methods, while sonication gave significantly lower recoveries. The optimised shake-flask method was applied to determine the distribution of TCA in naturally contaminated cork bark.     

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.     

Development of solid-phase extraction and solid-phase microextraction methods for the determination of chlorophenols in cork macerate and wine samples

Tri-, tetra- and pentachlorophenol (TCP, TeCP and PCP) can be considered the precursors in the formation of corresponding chloroanisoles, known to be powerful odorants in corks and wine. Determining the presence of these chlorophenolic compounds in cork soaking solutions (ethanol/water mixtures, 12% (v/v) ethanol used for cork quality control testing), or in wine can be achieved by acetylation/gas chromatography electron-capture detection. In order to reach the required sensitivity, a previous preconcentration step is necessary. Solid-phase extraction (SPE) and headspace solid-phase microextraction (HS-SPME) have given good results for the preconcentration of TCP, TeCP and PCP in such matrices. The use of Oasis HLB cartridges gives acceptable recoveries for the three compounds when different volumes (50-250 mL) of cork macerate with concentrations ranging from 20 to 150 ng/L are processed. Preconcentration based on HS-SPME has also been optimised with a 100 microm polydimethylsiloxane fibre and in situ derivatization. The HS-SPME method allows chlorophenols in a cork soaking solution and in wine to be determined with a limit of detection of 1 ng/L for each compound (in cork macerate) and a repeatability of around 0.5%-5% (n=8) for a concentration level of 30 ng/L.     

Quantification of chloroanisoles in cork using headspace solid-phase microextraction and gas chromatography with electron capture detection

Chloroanisoles can migrate from the cork stopper in wine bottles to the wine and give it a musty taint so it is important to find a method by which they can be determined. The aim of this paper is to develop a method for quantifying 2,4-dichloroanisole, 2,6-dichloroanisole, 2,4,6-trichloroanisole, 2,3,4,6-tetrachloroanisole and 2,3,4,5,6-pentachloroanisole in cork using headspace solid-phase microextraction and gas chromatography with electron capture detection. After we had prepared the cork standards that were so essential to the work we optimised the parameters that most influence headspace solid-phase microextraction: fibre coating, vial volume, cork, kind and volume of solvent to help the extraction, extraction temperature and time, ionic strength and stirring. The method quantifies the total amount of chloroanisoles in cork stoppers (natural, agglomerated, agglomerated with disks and sparkling wine stoppers), at suitable concentrations so that the capacity of these compounds to give wine a musty taint can be evaluated. The quantification limits are: 2,6-dichloroanisole (8.6 ng/g), 2,4,6-trichloroanisole (0.8 ng/g), 2,4-dichloroanisole (3.5 ng/g), 2,3,4,6-tetrachloroanisole (0.6 ng/g), 2,3,4,5,6-pentachloroanisole (0.8 ng/g). The other quality parameters are: recoveries (90.3-105.8%), repeatability (4-13% (RSD expressed)) and intermediate precision (5-14% (RSD expressed)).     

Development of a cellular biosensor for the detection of 2,4,6-trichloroanisole (TCA)

2,4,6-trichloroanisole (TCA) is a microbial metabolite formed from chlorophenols through the activity of several natural fungal strains present on the cork oak bark. TCA is the primary compound responsible for the mousty/mould off-odour known as “cork taint” present in cork stoppers, wine, water and alcoholic beverages. Chromatographic and electrochemical methods are currently used for the determination of TCA, however its detection at low concentrations remains a technical challenge. The aim of this study was the development of a rapid novel biosensor system based on the Bioelectric Recognition Assay (BERA). The sensor measured the electric response of cultured membrane-engineered fibroblast cells suspended in an alginate gel matrix due to the change of their membrane potential in the presence of the analyte. Membrane-engineered cells were prepared by osmotic insertion of 0.5 μg/l of specific TCA antibodies into the membrane of the cells. The BERA-based sensor was able to detect TCA in a few minutes (3-5 min) at extremely low concentrations (10⁻¹ ppt), thus demonstrating higher sensitivity than the human sensory threshold. In addition, the assay was quite selective against other haloanisoles and halophenols structurally related to or co-occurring with TCA. Finally the sensor was tested against real white wine samples from cork soaks. At this real test, the BERA sensor was able to detect TCA from cork soaks rapidly (3-5 min) at very low concentrations (1.02-12 ng/l), covering the whole range for the detection threshold for wines (1.4-10 ng/l). Therefore, this novel biosensor offers new perspectives for ultra-rapid, ultra-sensitive and low-cost monitoring of TCA presence in cork and wine and possibly also other food commodities.     

Development of a dispersive liquid-liquid microextraction method for the simultaneous determination of the main compounds causing cork taint and Brett character in wines using gas chromatography-tandem mass spectrometry

A novel dispersive liquid-liquid microextraction (DLLME) method, coupled to gas chromatography-tandem mass spectrometry (GC-MS/MS), was developed for simultaneously determining the main compounds responsible for cork taint (2,4,6-trichloranisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA), 2,4,6-tribromoanisole (TBA) and pentachloranisole (PCA)) and Brett character (4-ethylguaiacol (EG), 4-ethylphenol (EP), 4-vinylguaiacol (VG) and 4-vinylphenol (VP)) in wines. Optimisation of DLLME procedure was performed by evaluating the type of disperser and extraction solvents and the temperature and salt addition effects. The volumes of disperser and extraction solvents were also optimised by means of a central composite design combined with desirability functions. Under optimum conditions, 5 mL of wine were extracted with an extraction mixture consisting of 1.43 mL of acetone, and 173 μL of chloroform at room temperature. The analytical characteristics of the method were evaluated. Satisfactory linearity (with correlation coefficients over 0.992), repeatability (below 11.6%) and between-days precision (below 11.0%) were obtained for all target analytes. Detection limits attained were at similar levels or even lower than the olfactory threshold of the studied compounds. Finally, the developed method was successfully applied to the analysis of wine samples. To our knowledge, this is the first time that DLLME has been applied to simultaneously determine the compounds responsible for cork taint and Brett character in wine.     

Multiple response optimisation based on desirability functions of a microwave-assisted extraction method for the simultaneous determination of chloroanisoles and chlorophenols in oak barrel sawdust

A microwave-assisted extraction (MAE) method was optimised for extracting 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA), pentachloroanisole (PCA), 2,4,6-trichlorophenol (TCP), 2,3,4,6-tetrachlorophenol (TeCP) and pentachlorophenol (PCP) from oak barrels. The method was optimised by using a central composite experimental design with extraction time, temperature and solvent volume as influential parameters. A desirability function was then employed in addition to the simultaneous optimisation of the compounds. The optimal conditions identified were temperature 130 degrees C, solvent volume 35 mL and extraction time 50 min. The compounds were determined by gas chromatography with electron-capture detection. MAE was compared with conventional Soxhlet extraction; the results obtained with MAE were in good agreement with those obtained by Soxhlet extraction.     

Determination of chloroanisole compounds in red wine by headspace solid-phase microextraction and gas chromatography-mass spectrometry

The objectives of this study, were the development and validation of an analytical method for the determination of 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA) and pentachloroanisole (PCA) in red wine by headspace solid-phase microextraction and GC-MS as well as the application of the optimized and validated method for the quatification of chloroanisoles in different red wines from Navarra. To carry out this study, the extraction variables have been optimized. The fiber and the experimental design selected permit the determination of low analyte concentrations (ng/L) with good accuracy (<5%). Moreover, an analytical method for the determination of TCA and TeCA in wine by GC-MS has been validated. The results obtained in the validation step, recovery values, detection and quantitative limits, and precision were acceptable for all the analytes in the ranges of concentration studied (<5% and <10% for TCA and TeCA, respectively). This method has been used as an analytical method for the quantification of TCA and TeCA in red wine samples that were selected for this study, yielding good results.     

Highly selective solid-phase extraction and large volume injection for the robust gas chromatography-mass spectrometric analysis of TCA and TBA in wines

A reliable solid-phase extraction (SPE) method for the simultaneous determination of 2,4,6-trichloroanisole (TCA) and 2,4,6-tribromoanisole (TBA) in wines has been developed. In the proposed procedure 50 mL of wine are extracted in a 1 mL cartridge filled with 50 mg of LiChrolut EN resins. Most wine volatiles are washed up with 12.5 mL of a water:methanol solution (70%, v/v) containing 1% of NaHCO3. Analytes are further eluted with 0.6 mL of dichloromethane. A 40 microL aliquot of this extract is directly injected into a PTV injector operated in the solvent split mode, and analysed by gas chromatography (GC)-ion trap mass spectrometry using the selected ion storage mode. The solid-phase extraction, including sample volume and rinsing and elution solvents, and the large volume GC injection have been carefully evaluated and optimized. The resulting method is precise (RSD (%) < 6% at 100 ng L(-1)), sensitive (LOD were 0.2 and 0.4 ng/L for TCA and TBA, respectively), robust (the absolute recoveries of both analytes are higher than 80% and consistent wine to wine) and friendly to the GC-MS system (the extract is clean, simple and free from non-volatiles).     

Molecularly imprinted polymer surfaces as solid-phase extraction sorbents for the extraction of 2-nitrophenol and isomers from environmental water

The novel surface molecularly imprinted polymer (MIP) with 2‐nitrophenol (2‐NP) as the template has been prepared and used as the adsorbent for the solid‐phase extraction (SPE). The selectivity of the polymer was checked toward several selected nitrophenols (NPs) such as 2‐NP, 3‐nitrophenol (3‐NP), 4‐nitrophenol (4‐NP) and 2,4,6‐trichlorophenol (2,4,6‐TCP). Under the optimized conditions, high sensitivity (detection limits: 0.07–0.12 ng/mL) and good reproducibility of analytes (2.3–4.8% for four cycles) were achieved. Then, the method was applied for the analysis of selected phenols in spiked tap, lake and river water samples. High recoveries (>83.3%) for nitrophenols (NPs) were obtained, but lower recoveries (<63.4%) were achieved for 2,4,6‐TCP. The method was found to be linear in the range of 1–300 ng/mL with correlation coefficients (R²) greater than 0.99 and repeatability relative standard deviation (RSD) below 7.2% in all cases. For analysis of 120 mL water samples, the method detection limits (LODs) ranged from 0.10 to 0.22 ng/mL and the limit of quantification (LOQs) from 0.33 to 0.72 ng/mL. These results showed the suitability of the MIP‐SPE method for the selective extraction of a group of structurally related isomeric compounds.     

Determination of 2,4,6-trichloroanisole and guaiacol in cork stoppers by pressurised fluid extraction and gas chromatography-mass spectrometry

This paper describes the development of an analytical method consisting of pressurised fluid extraction (PFE) and gas chromatography-mass spectrometry (GC-MS) using experimental designs to determine two volatile compounds in naturally-tainted cork stoppers. The target analytes, 2,4,6-trichloroanisole (2,4,6-TCA) and guaiacol, are involved in the cork taint of wine. First, a Plackett-Burman experimental design was carried out in order to determine the significant experimental parameters affecting the PFE process, and then a central composite design was used to optimise these significant parameters. Once the method had been optimised, the influence of the number of extraction cycles was studied. The method was applied to determine the concentration of 2,4,6-TCA and guaiacol in three cork samples, and the results were compared with the ones obtained by multiple headspace-solid-phase microextraction (MHS-SPME) and by Soxhlet extraction.     

Application of fractional factorial experimental and Box-Behnken designs for optimization of single-drop microextraction of 2,4,6-trichloroanisole and 2,4,6-tribromoanisole from wine samples

In this paper a new method for the determination of 2,4,6-trichloroanisole (TCA) and 2,4,6-tribromoanisole (TBA) in wine samples is presented. Headspace single-drop microextraction (HS-SDME) was used for the extraction and preconcentration of the analytes, followed by analysis by gas chromatography and electron-capture detection (GC-ECD). The variables affecting extraction efficiency were optimized using fractional factorial experimental and Box-Behnken designs. The external calibration procedure was successfully carried out using a synthetic wine solution and diluted red wine samples. The method was also applied to white wine samples. Excellent detection limits of 8.1 and 6.1 ng L(-1) were achieved for TCA and TBA, respectively. Good precision and accuracy were obtained.     

纺织品中残留氯酚的毛细管气相色谱测定法

采用稀硫酸浸湿样品,正己烷提取,乙酸酐衍生后以毛细管气相色谱分离测定的方法对纺织品中五氯酚、三氯酚残留量进行了同时测定,探讨了提取、净化及色谱分析条件。方法回收率范围三氯酚84.8％～98.1％,五氯酚88.0％～100.2％。相对标准偏差三氯酚1.54％～2.33％,五氯酚3.48％。方法的检出限（质量分数）分别为2,4,6-三氯酚1.0×10