Biomedical subjects

O Busto

Publications and source records attributed to O Busto.

16 recordsLinked to original sources

PubMed2006

Comparative study of two chromatographic methods for quantifying 2,4,6-trichloranisole in wines.

Here we present the validation and the comparative study of two chromatographic methods for quantifying 2,4,6-trichloroanisole (TCA) in wines (red, rosé and white wines). The first method involves headspace solid-phase microextraction and gas chromatography with electron-capture detection (ECD). The evaluation of the performance parameters shows limit of detection of 0.3 ng l(-1), limit of quantification of 1.0 ng l(-1), recoveries around 100% and repeatability of 10%. The second one implies a headspace solid-phase microextraction and gas chromatography with mass spectrometric detection. The performance parameters of this second method are limit of detection of 0.2 ng l(-1), limit of quantification of 0.8 ng l(-1) and repeatability of 10.1%. From the comparative study we can state that both methods provide similar results and the differences between them are the better sensitivity of the GC-ECD method and the very shorter chromatogram running time of the GC-MS method. The two methods are able to quantify TCA below the sensorial threshold in red, rosé and white wines using just a calibration graph, thus they could be a very good tool for quality control in wineries.

Anisoles↗

PubMed2006

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)).

Anisoles↗

PubMed2003

Fast screening method for determining 2,4,6-trichloroanisole in wines using a headspace-mass spectrometry (HS-MS) system and multivariate calibration.

The system based on coupling a headspace sampler to a mass spectrometer (HS-MS), which is considered one kind of electronic nose, is an emergent technique for ensuring and controlling quality in industry. It involves injecting the headspace of the sample into the ionization chamber of the mass spectrometer where the analytes are fragmented. The result is a complex mass spectrum for each sample analyzed. When several samples are analyzed the data matrix generated is processed with chemometric techniques to compare and classify the substances from their volatile composition, in other words, to compare and classify their flavor. So far, information from electronic nose applications has mainly been qualitative. In this paper we present a quantitative study that uses a multivariate calibration. We analyzed several white wines using HS-MS to determine 2,4,6-tricholoranisole (TCA). This is an off-flavor that is a serious problem for the wine industry. The method is simple because it does not require sample preparation, only addition of sodium chloride being necessary for sample conditioning. Also, it provides a fast screening (10 min/sample) of the quantity of TCA in wines at ultratrace (sub microg L(-1)) levels.

Anisoles↗

PubMed2002

Determination of 2,4,6-trichloroanisole in wines by headspace solid-phase microextraction and gas chromatography-electron-capture detection.

One of the most important problems in the wine world, today, is cork taint, which often has been chemically identified as 2,4,6-trichloroanisole (TCA). The perception limit of this compound is very low (close to 10 and 40 ng/l for white and red wines, respectively), so, even at such low concentrations, its presence becomes a problem in wine quality. A method for the analysis of TCA in white and red wines has been developed in our laboratory, using headspace solid-phase microextraction and gas chromatography with electron-capture detection. The method, which has been optimized using an experimental design, involves the use of fibres coated with polydimethylsiloxane (PDMS) and allows the analysis of TCA at very low concentrations (under 500 ng/l) with good accuracy (RSD < or = 10%). The limits of quantification of the method are 5 and 8 ng/l for white and red wines, respectively, while the limit of detection is 1 ng/l for both types of wine.

Anisoles↗

PubMed2002

Determination of 4-ethylguaiacol and 4-ethylphenol in red wines using headspace-solid-phase microextraction-gas chromatography.

A method for analysing 4-ethylguaiacol and 4-ethylphenol in the aroma of red wines using headspace-solid-phase microextraction is presented. The fibres used were coated with 100 microm of polydimethylsiloxane. Parameters like ionic strength, agitation of the sample, sample volume, temperature of the sample and adsorption/desorption times were studied and optimised to obtain the best extraction results. The linearity of the response was studied in the usual concentration ranges in wines (4-ethylguaiacol, 40-400 microg/l; 4-ethylphenol, 200-1800 microg/l). Repeatability of the method was determined, and the relative standard deviation was about 10%. Limits of detection and limits of quantification were also determined, and the values found were 1 and 5 microg/l for 4-ethylguaiacol and 2 and 5 microg/l for 4-ethylphenol, respectively. All these values were under the sensory thresholds established for these volatile phenols. The presence of interferences due to the matrix composition implies the use of the standard addition technique for both compounds quantification.

Chromatography, Gas↗

PubMed2002

Headspace solid-phase microextraction of higher fatty acid ethyl esters in white rum aroma.

Fatty acid ethyl esters are the main components of rum aroma and play an important sensorial impact in these distilled alcoholic beverages. Herein, a method for analysing these volatile compounds is described. It involves a separation and concentration step using headspace solid-phase microextraction and determination by capillary gas chromatography using flame ionisation detection. The influence of different parameters related to the isolation and concentration step, such as ethanol concentration, ionic strength, sample volume, time and temperature of extraction, was studied. The developed method enabled recoveries >91% for the analyzed compounds with limits of detection between 0.007 and 0.027 mg/l, all of them lower than the range of concentrations found in rum samples. The method was successfully applied to the analysis of fatty acid ethyl esters in different commercial white rums.

Alcoholic Beverages↗

PubMed2002

Headspace solid-phase microextraction analysis of 3-alkyl-2-methoxypyrazines in wines.

A procedure to determine 3-alkyl-2-methoxypyrazines in wines is described. It is based on the headspace solid-phase microextraction (HS-SPME) technique after a clean-up of the sample by distillation (previously acidified to pH 0.5) to remove ethanol and other volatile compounds that can interfere in the SPME. Determination is performed by means of capillary gas chromatography using a nitrogen-phosphorus detector. The method allows quantification of 3-isobutyl-2-methoxypyrazine, 3-sec-butyl-2-methoxypyrazine and 3-isopropyl-2-methoxypyrazine at their natural concentration levels and below their sensory thresholds in Cabernet Sauvignon and Merlot wines. The method was successfully applied to experimental red wines and the evolution of their pyrazine contents during the winemaking process was monitored. Pyrazine content increased during the first maceration day but did not change significantly during alcoholic and malolactic fermentation. Final contents in wines were 12-27 ng/l of 3-isobutyl-2-methoxypyrazine and 5-10 ng/l of 3-sec-butyl-2-methoxypyrazine.

Chromatography, Gas↗

PubMed2002

Application of headspace solid-phase microextraction to the determination of sulphur compounds with low volatility in wines.

Headspace solid-phase microextraction (HS-SPME) has been used for determining sulphur compounds with low volatility in wines. With this technique, handling of samples is minimal so undesirable loses and reactions between compounds are prevented. Furthermore, this kind of extraction is fast and does not require any organic solvent. Under optimal conditions, the HS-SPME, using a new fibre coated with Stable Flex divinylbenzene-Carboxen-polydimethylsiloxane, makes possible the quantification of sixteen sulphur compounds with low volatility which may be present in wines. The limits of detection for the analytes studied ranged between 0.05 and 10 microg/l, and the recovery and repeatability found were acceptable. The method developed was successfully applied to determine the concentration of the target analytes in varietal wines from the Catalonian region (Spain) with some aromatic defects such as an odour of rubber, onion, rotten, unpleasant herbaceous, etc. The results show that the contents of the sulphur compounds studied in these wines are higher than in those without defects. This shows a relationship exists between the presence of sulphur compounds and the quality of the wine aroma.

Chromatography, Gas↗

PubMed2000

Solid-phase extraction applied to the determination of ochratoxin A in wines by reversed-phase high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic method is described for the analysis of Ochratoxin A at low microg l(-1) levels in samples of artificially contaminated wines. The method involves solid-phase extraction of samples using octadecylsilane cartridges and an additional preconcentration step prior to chromatography with isocratic elution and fluorimetric detection. The method was evaluated for accuracy and precision with relative standard deviations lower than 10%. Recoveries of ochratoxin A added to commercial wines over the range 0.1-3.0 microg l(-1) were higher than 80% in the assays. The performance of the octadecylsilane cartridge method tested compared very favourably with results of other published studies of ochratoxin A which use immunoaffinity columns or solvent extraction techniques.

Chromatography, High Pressure Liquid↗

PubMed2000

Analysis of organic sulfur compounds in wine aroma.

Sulfur-containing compounds in wines have been extensively studied because of their effect on wine aroma. The aim of this paper was to give an overview on the analytical methods developed to determine them in wines with special emphasis on gas chromatographic methods, as well as the results obtained. In addition, the problems occurring in application of the common extraction procedures, such as liquid-liquid extraction, static and dynamic headspace and solid-phase microextraction, are presented and discussed.

Sulfur Compounds↗

PubMed2000

Analysis of low-volatility organic sulphur compounds in wines by solid-phase microextraction and gas chromatography.

A method for analysing low-volatility sulphur compounds using solid-phase microextraction has been developed. The analytes were extracted directly from the liquid sample using fibres coated with different stationary phases. The best extraction efficiency was obtained with Carboxen-polydimethylsiloxane coating. Ionic strength, sample volume, time and temperature of the extraction were optimised and the matrix effect studied. The method enables 15 sulphur compounds in wine to be determined at trace levels with recoveries close to 100% and limits of detection between 0.05 and 5 microg/L. The overall method was successfully applied to the determination of the sulphur compounds studied in several red, white and rosé wines.

Chromatography, Gas↗

PubMed2000

Headspace solid-phase microextraction method for determining 3-alkyl-2-methoxypyrazines in musts by means of polydimethylsiloxane-divinylbenzene fibres.

A method for determining 2-methoxypyrazine, 3-methyl-, 3-ethyl-, 3-isopropyl-, 3-sec.-butyl- and 3-isobutyl-2-methoxypyrazine in musts is described. It involves headspace solid-phase microextraction (SPME) and determination by capillary gas chromatography using nitrogen-phosphorous detection. Pyrazines were satisfactorily separated under isothermal conditions, and quantification was carried out using 3-isopropyl-2-ethoxypyrazine as the internal standard. Ionic strength, time and temperature were studied in order to make SPME as efficient as possible. The developed method enabled detection limits at the 0.1 ng(-1) levels for some of the analytes. The method was successfully applied to identify and quantify different 3-alkyl-2-methoxypyrazines in experimental musts of Cabernet Sauvignon and Merlot. Their evolution during the ripening was also monitored.

Osmolar Concentration↗

PubMed1999

Simultaneous analysis of thiols, sulphides and disulphides in wine aroma by headspace solid-phase microextraction-gas chromatography.

This paper deals with the improvement of a headspace solid-phase microextraction (HS-SPME) method, developed in a previous work, in order to analyse, simultaneously, thiols, sulphides and disulphides in wines. This can be achieved by applying Carboxen-polydimethylsiloxane fibres and a cryogenic trap to focus the analytes. Under optimum conditions, the HS-SPME procedure developed shows low limits of detection for the sulphides and disulphides studied (0.05-3 micrograms/l) and the thiols can also be analysed and detected at very low levels (0.5-1 microgram/l) with acceptable recoveries and repeatability.

Chromatography, Gas↗

PubMed1999

Headspace solid-phase microextraction of sulphides and disulphides using Carboxen-polydimethylsiloxane fibers in the analysis of wine aroma.

Headspace solid-phase microextraction was applied to gas chromatography coupled to flame photometric detection to develop a method for analysing volatile sulphides and disulphides in wine. The Carboxen-polydimethylsiloxane-coated silica fiber was tested and different parameters such as presampling time, ionic strength, stirring, headspace volume, ethanol concentration, time and temperature of extraction were optimized to make extraction as efficient as possible. The optimized conditions enabled limits of detection to be obtained at the ng/l levels. The fiber tested has a strong affinity for the sulphur compounds studied and enables these analytes to be quantitatively determined in wines. The Carboxen-polydimethylsiloxane-coated fiber is more efficient at extracting than fibers such as those which are polydimethylsiloxane-coated and polyacrylate-coated, but its repeatability is worse. The overall process was successfully applied to identify and quantify sulphur compounds in white, red, rose and vintage wines.

Adsorption↗

PubMed1998

Headspace solid-phase microextraction analysis of volatile sulphides and disulphides in wine aroma.

Sulphur compounds (S-compounds) are important constituents of wine off-flavours. Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography coupled to flame photometric detection (GC-FPD) was used to develop a suitable method to analyse volatile sulphides and disulphides. This is a very simple and fast technique which gives good reproducibility at microgram/l levels (relative standard deviations < 10%). The analytes were extracted from the headspace of the samples by using either polydimethylsiloxane or polyacrylate coated fused-silica fibers in an SPME unit. Then, the fiber was inserted into the injector of a gas chromatograph and the extracted S-compounds were thermally desorbed. The influence of different parameters, such as ionic strength, stirring, headspace volume, ethanol concentration, time and temperature of extraction, was studied. The extraction of the fibers varies considerably for the different sulphur compounds studied. The most volatile compounds were the least extracted by the coating fibers tested. The standard additions technique, applied to real samples, gave the recoveries > 94%. The detection limits range between 3 micrograms/l and 50 ng/l. The overall process was successfully applied to identify and quantify S-compounds in white and red wines.

Chromatography, Gas↗

PubMed1997

Chromatographic analysis of volatile sulphur compounds in wines, using the static headspace technique with flame photometric detection.

This study describes the development of a method for determining eleven sulphur compounds in wine, which takes into account that thiols are easily oxidizable. The equilibria of the analytes between air and aqueous ethanol were studied and optimised using static headspace gas chromatography in order to obtain the best sensitivities. The influences of parameters such as temperature, time, ionic strength, headspace volume and the volume of headspace injected were determined. A cryogenic trap was used to concentrate the headspace analytes and they were chromatographically analysed using GC temperature programming on a poly(ethylene glycol) capillary column with FPD detection at 394 nm. The power relationship was observed between the chromatography response and a concentration of sulphur compounds in the range 2-150 micrograms l(-1) in the sample. Recoveries were determined by the standard addition technique and were higher than 90% for sulphides and disulphides and close to 80% for thiols. The overall method was successfully used to determine the sulphur compounds in white and red wines.

Chromatography, Gas↗