Josep Guasch

Determination of biogenic amines in wines by high-performance liquid chromatography with on-column fluorescence derivatization

An on-column fluorometric derivatization method was developed for determining eight biogenic amines by HPLC and fluorometric detection. The derivatization was carried out by pumping the o-phthalaldehyde reagent through the column together with other solvents used as mobile phases. The on-column reaction conditions (pH, borate and o-phthalaldehyde concentrations) were optimized. The matrix effect, the thiol used in the derivative reagent and the effect of the temperature on the separation process were also studied. Solid-phase extraction was applied prior to the derivatization procedure as a clean-up of wines by using 2 different commercially available SAX and C18 cartridges to improve the accuracy and the precision of the method. The linearity range (0.5–15 mg 1−1) and detection limits (between 100 and 300 μg l−1) of this method were similar to the standard pre-column automated o-phthalaldehyde derivatization method. The method was checked with several red wines from Tarragona by comparing the results with the standard pre-column method.

Determination of biogenic amines in wine after precolumn derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate

Abstract AQC (6-aminoquinolyl-N-hydroxysuccinimidyl carbamate) was used as an alternative to the most common derivatization reagent, OPA (o-phthaldialdehyde), to determine sixteen biogenic amines in wines. OPA and AQC were compared in terms of the range of linearity, the limit of detection and the sensitivity (calibration line slopes) resulting from the application of each of the derivatization reagents. Sample handling is minimal because derivatization is fully automated by means of an injection programme. After derivatization, the derivatives were analysed by reversed-phase liquid chromatography with gradient elution and fluorimetric detection. All the amines studied eluted in less than 25 min under the optimum conditions established. Different variables that effect derivatization and separation were optimized. Good linearity of the responses was obtained between 0.05 and 10.00 mg l−1 depending on the amine derivative. The detection limits ranged between 5 and 50 μg l−1 for standard solutions and between 100 and 500 μg l−1 for wines. The method was successfully applied to the determination of the above amines in several types of wines from the Tarragona region.

Improvement of a solid-phase extraction method for determining biogenic amines in wines

Abstract Solid-phase extraction (SPE) was used simultaneously to clean up and concentrate samples prior to automatic derivatization to determine fifteen biogenic amines in wine. In the first step, SPE was used to remove polyphenolic compounds which interfere with further extraction and chromatographic analysis; in this study, treatments with polyvinylpyrrolidone, SAX and C18 cartridges were tested and compared. In the second step, C18 cartridges were used to concentrate the analytes after adding sodium octanesulfonate, sodium decanesulfonate and sodium dodecanesulfonate as ion-pair reagents. Reversed-phase chromatography with fluorimetric detection was performed on the extracted amines after automatic precolumn derivatization by treatment with o-phthalaldehyde. Biogenic amines can be separated and detected after the solid-phase extraction with an average sensitivity of the order of 20–90 μg l−1. Recoveries were determined by the standard addition technique and the overall method was successfully applied to the determination of the above-mentioned amines in red wines from the Tarragona region.

Solid phase extraction applied to the determination of biogenic amines in wines by HPLC

SummaryA method suitable for the determination of 19 biogenic amines in wine has been developed. The method involves derivatization of amines by treatment with dansyl chloride and solid-phase extraction of the derivatives. Prior to the derivatization procedure, clean-up of the wine sample with polyvinylpyrrolidone is carried out. Reversed-phase gradient elution HPLC with UV detection at 250 nm was used to determine these compounds. Some consideration was given to the effect of temperature on the separation process. Linearity of derivatization was obtained for amounts of all the biogenic amines ranging from 500 μg·L−1 to 20 mg·L−1. Limits of detection (signal-to-noise ratio=3) of the amines were similar for all the dansylderivatives (between 50 and 150 μg·L−1). Addition of standard amines was used for the determination of amine recoveries. These were better than 85% for ethanolamine, tryptamine, phenetylamine, putrescine, cadaverine and histamine. The overall process was succesfully applied to identify and quantify biogenic amines in white and red wines.

Application of FT-MIR Spectroscopy for Fast Control of Red Grape Phenolic Ripening

The content of phenolic compounds determines the state of phenolic ripening of red grapes and is a key criterion in setting the harvest date to produce quality red wines. In this study, the feasibility of Fourier transform mid-infrared (FT-MIR) spectroscopy combined with partial least-squares (PLS) regression to quantify phenolic compounds is reported. The reference methods used for quantifying these compounds (which were evaluated as total phenolic compounds, total anthocyanins, and condensed tannins) were the usual ones used in cellars that employed UV-vis spectroscopy. To take into account the high natural variability of grapes when building the calibration models, fresh grapes from six varieties, at different phenolic ripening states were harvested during three vintages. Destemmed and crushed grapes were subjected to an accelerated extraction process and used as calibration standards. A total of 192 extracts (objects) were obtained, and these were divided into a training set (106 objects) and a test set (86 objects) to evaluate the predictive ability of the models. Among the different MIR regions of the extract raw spectra, those that provided the highest variability on the absorption were selected. The results showed that the best PLS regression model was the one obtained when working in the region of 1168-1457 cm(-1) because it gave the most accurate and robust prediction for total phenolic compounds (RMSEP%=4.3 and RPD=4.5), total anthocyanins (RMSEP%=5.9 and RPD=3.5), and condensed tannins (RMSEP%=5.8 and RPD=3.8). Therefore, it can be concluded that FT-MIR spectroscopy can be a fast and reliable technique for monitoring the phenolic ripening in red grapes during the harvest period.

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.

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.

Determination of biogenic amines in wine after clean-up by solid-phase extraction

SummaryA suitable method for the determination of 16 biogenic amines in wine has been developed. The method involves clean-up of wine samples using ion-exchange cartridges and a preconcentration step, under controlled vacuum, before derivatization of the amines by treatment with phthalaldehyde (PA) and reversedphase HPLC with gradient elution and fluorimetric detection. Linearity of response was obtained for all the biogenic amines from 100 μg L−1 to mg L−1. Limits of detection for the amines were similar for all PA-derivatives (25–50 μg L−1) and the quantitation limits were about 0.1 mg L−1. After clean-up and preconcentration, the concentration levels increased 10-fold for all amines except putrescine and cadaverine, which gave poor recovery by this method unlike the rest which gave recoveries of almost 90%. The overall process was successfully applied to identify and quantify biogenic amines in several red wines from the Tarragona region.

Validation of bias in multianalyte determination methods.: Application to RP-HPLC derivatizing methodologies

This paper reports a new approach for validating bias in analytical methods that provide simultaneous results on multiple analytes. The validation process is based on a linear regression technique taking into account errors in both axes. The validation approach is used to individually compare two different chromatographic methods with a reference one. Each of the two methods to be tested is applied on a different set of data composed of two real data sets each. In addition, three different kinds of simulated data sets were used. All three methods are based on RP-high-performance liquid chromatography (HPLC) and are used to quantify eight biogenic amines in wine. The two methods to be tested use different derivatizing procedures: precolumn 6-aminoquinolyl-n-hydroxysuccinimidyl carbamate (AQC) and oncolumn o-phtalaldehyde (OPA), respectively. On the other hand, the reference method uses derivatization with OPA precolumn. Various analytes are determined in a set of samples using each of the methods to be tested and their results are regressed independently against the results of the reference method. Bias is detected in the methods to be tested by applying the joint confidence interval test to the slope and the intercept of the regression line which takes into account uncertainties in the two methods being compared. The conclusions about the trueness of the two methods being tested varied according to whether the joint confidence interval test was applied to data obtained from various biogenic amines considered simultaneously or individually.

Quantification of phenolic compounds during red winemaking using FT-MIR spectroscopy and PLS-regression.

We present a rapid method to quantify phenolic compounds all during the red winemaking process using Fourier transform mid-infrared (FT-MIR) spectroscopy and chemometrics. To get the reference values, we used the usual UV–vis spectroscopy methods, and the compounds studied were evaluated as total phenolic compounds (TPC), total anthocyanins (TA), and condensed tannins (CT). Sampling from five different grape varieties (Merlot, Tempranillo, Syrah, Cariñena, and Cabernet sauvignon), harvested at different ripening states, and monitored over 10 days of vinification produced a total of 600 spectra. These were used to build and validate four different predictive models by partial least-squares (PLS) regression. The spectral regions selected for each model were between 979 and 2989 cm(–1), and when selecting the most suitable one in each case, good values of performance parameters were obtained (R2(val) > 0.95 and RPD > 4.0 for TPC; R2(val) > 0.90 and RPD > 3.0 for TA; R2(val) < 0.8 and RPD < 3.0 for CT). Furthermore, also more specific PLS regression models for each phenolic parameter and each grape variety were developed using different regions with results similar to those obtained when dealing with all of the grape varieties. It is concluded that FT-MIR spectroscopy together with multivariate calibration could be a rapid and valuable tool for wineries to carry out the monitoring of phenolic compound extraction during winemaking.