Method for analyzing a cork stopper for the presence of 2,4,6-trichloroanisole and device for performing the same

Abstract

A non-destructive method for analyzing a cork stopper for the presence of 2,4,6-trichloroanisole. The stopper is introduced into a hermetically closed container. The container containing the stopper is heated under conditions vaporizing any 2,4,6-trichloroanisole present in the stopper. A gaseous sample of the atmosphere surrounding the stopper in the container is collected and analyzed for the presence of 2,4,6-trichloroanisole. This method allows the selection, in a batch of cork stoppers, of the stoppers that are substantially free of 2,4,6-trichloroanisole, in a non-destructive manner.

Claims

1. A method for analyzing a cork stopper for a presence of 2,4,6-trichloroanisole, comprising the steps of successively: introducing only the cork stopper into a container; hermetically closing the container; heating the container containing the cork stopper to vaporize any 2,4,6-trichloroanisole present in the cork stopper; collecting a gaseous sample of an atmosphere surrounding the cork stopper in the container, by collecting a fraction of an overall atmosphere present in the container and surrounding the cork stopper, said gaseous sample having a composition identical to the composition of the atmosphere; and analyzing the gaseous sample for the presence of 2,4,6-trichloroanisole.

2. The method as claimed in claim 1, further comprising the step of heating the container containing the cork stopper at a temperature of between 50 and 75 C., at atmospheric pressure and for a time between 45 and 90 minutes.

3. The method as claimed in claim 2, further comprising the step of heating the container containing the cork stopper at the temperature of between 50 and 75 C., at the atmospheric pressure and for 60 minutes.

4. The method as claimed in claim 1, wherein the step of analyzing the gaseous sample comprises the step of quantifying the 2,4,6-trichloroanisole present in the gaseous sample.

5. The method as claimed in claim 1, wherein the step of analyzing the gaseous sample for the presence of 2,4,6-trichloroanisole comprises the step of performing a gas chromatography by injecting the gaseous sample collected in the container directly into a gas chromatograph coupled to a detector.

6. The method as claimed in claim 5, further comprising the step of selecting a detection method utilized by the detector from one of the following: a mass spectrometry, an electron uptake, an ion mobility spectrometry or an ion mobility mass spectrometry.

7. The method as claimed in claim 1, wherein the steps are performed in an automated manner.

8. The method as claimed in claim 1, wherein the step of hermetically closing the container is performed using a closure equipped with a wall that can be pierced with a syringe needle.

9. The method as claimed in claim 1, wherein the step of analyzing the gaseous sample for the presence of 2,4,6-trichloroanisole comprises the step of performing a gas chromatography; and wherein the step of collecting the gaseous sample of the atmosphere surrounding the cork stopper in the container is performed directly with a syringe of a gas chromatograph injection system.

10. A process for selecting cork stoppers from a batch of cork stoppers that are substantially free of 2,4,6-trichloroanisole, comprising the steps of successively: analyzing each cork stopper in the batch for the presence of 2,4,6-trichloroanisole as claimed in claim 1; and selecting said each cork stopper when the presence of 2,4,6-trichloroanisole is not detected.

11. The selection process as claimed in claim 10, further comprising the steps of determining a value representative of a concentration of 2,4,6-trichloroanisole in the gaseous sample for said each cork stopper in the batch; and additionally performing the following steps for said each cork stopper having a non-zero representative value: comparing the representative value of said each cork stopper with a predetermined threshold value; and selecting said each cork stopper having the representative value which is less than or equal to the threshold value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The characteristics and advantages of the invention will emerge more clearly in light of the implementation example below, which is given purely as an illustration of the invention and in no way limiting the same, with the support of FIGS. 1 to 3, in which:

(2) FIG. 1 schematically shows an automated device for performing the final steps of a method according to the invention for analyzing a cork stopper for the presence of 2,4,6-trichloroanisole;

(3) FIG. 2a shows an example of a chromatogram obtained after performing a method according to the invention, for analyzing a cork stopper for the presence of 2,4,6-trichloroanisole;

(4) FIG. 2b shows a chromatogram obtained for a 2 ng/l solution of 2,4,6-trichloroanisole in ethanol, analyzed under the same conditions as for the production of the chromatogram of FIG. 2a; and

(5) FIG. 3 shows a graph representing, for 10 stoppers individually analyzed, successively by a method in accordance with the invention and by the SPME method of the prior art, the area under the peak measured at the retention time of 2,4,6-trichloroanisole by performing the method according to the invention, as a function of the concentration of 2,4,6-trichloroanisole measured by the SPME method.

DETAILED DESCRIPTION OF THE INVENTION

(6) A method according to the invention for analyzing a cork stopper for the presence of 2,4,6-trichloroanisole comprises the following steps.

(7) Firstly, a cork stopper is placed in a container 11, for example having a volume of 100 ml.

(8) This container 11 is hermetically closed, especially using a closing member suited to the injection system of a gas chromatograph.

(9) These first steps may be performed manually or in an automated manner, by adequate automatic modules that are standard per se for the introduction in series of solid articles into individual containers and the closure of these containers.

(10) The container 11 containing a stopper is then subjected to a step of heating, at a temperature of between 50 and 75 C., more precisely at 70 C., at atmospheric pressure, for 1 h. These heating conditions bring about the release of at least part of the 2,4,6-trichloroanisole that may be contained in the cork, in gaseous form, in the internal atmosphere of the container 11, and the stabilization in an equilibrium state.

(11) A sample, for example 0.5 ml, of the atmosphere present in the container 11 containing the stopper, is then collected from the container 11 and analyzed for the presence of 2,4,6-trichloroanisole.

(12) This analysis is performed, for example, by gas chromatography and detection by electron uptake.

(13) An example of a device for the serial and automated implementation of these steps of the method according to the invention is shown schematically in FIG. 1.

(14) This device comprises a module 21 for receiving containers 11 each containing a cork stopper.

(15) From this reception module 21, the containers 11 are transported, via a conveyor 22, which is standard per se, through a heating tunnel 23. This heating tunnel may be of any type that is standard per se.

(16) The heating power of the heating tunnel 23 and the speed of the conveyor 22 are adjusted so that each container 11 is subjected, in the heating tunnel 23, to a temperature of between 50 and 75 C. for 1 h.

(17) At the exit of the heating tunnel 23, the container 11 is conveyed, still by the conveyor 22, to a sample collection module 24 for the collection of a gaseous sample of the internal atmosphere of the container 11 surrounding the stopper. This collection is preferentially performed by the automatic injection system of a gas chromatograph. In FIG. 1, reference 25 denotes, as a whole, this chromatograph and a combined detector.

(18) The gaseous sample thus collected is injected into the chromatograph, and analyzed for the presence of 2,4,6-trichloroanisole.

(19) On exiting the sample collection module 24, the container 11, still containing the stopper, is transported by the conveyor 22 to a module 26 for collecting the containers, in order to sort them as a function of the results of the analysis by gas chromatography.

(20) The device may also comprise a sorting module for the automated sorting of the containers, as a function of the results of the analysis for the presence of 2,4,6-trichloroanisole performed by the gas chromatograph and the associated detector. This sorting module, which is not shown in the figures, is advantageously controlled by a control module which the device comprises. The control module is especially capable of acquiring the data recorded by the detector for each container 11, processing them and emitting, for each container 11, a control signal to the sorting module, established as a function of the result of the analysis for the presence of 2,4,6-trichloroanisole, so as to ensure separation of the containers 11 as a function of the presence of 2,4,6-trichloroanisole in the stoppers they contain, and/or of the measured concentration of TCA.

(21) The gas chromatograph 25 is conventional per se.

(22) It is equipped, for example, with two analytical pathways, each being composed of an injector, an injection valve, a short capillary column and a detector, for example by electron uptake. This advantageously makes it possible to perform two analyses simultaneously. Preferentially, the two analytical pathways are managed by the same control module.

(23) By way of example, an ordinary cork stopper was subjected to the above steps. The gaseous sample collected from the container 11 containing it was analyzed by gas chromatography, on a polydimethylsiloxane column with a phase thickness of 5 m, coupled to an electron-uptake detector. A 2 ng/L calibration solution of 2,4,6-trichloroanisole in ethanol was also prepared and injected into the chromatograph, under the same operating conditions.

(24) The chromatograms obtained are shown in FIG. 2a for the sample treated in accordance with the invention, and in FIG. 2b for the 2,4,6-trichloroanisole calibration solution.

(25) It is seen in these figures that the chromatogram obtained according to the invention has a peak at 1.697 minutes, which may indeed be attributed to 2,4,6-trichloroanisole, the control chromatogram of which shows a retention time of 1.716 minutes.

(26) In a more global selection process, in a batch of cork stoppers, stoppers substantially free of 2,4,6-trichloroanisole, this stopper is discarded since it is contaminated with 2,4,6-trichloroanisole and thus liable to give wine a corky flavor.

(27) The quantification of the content of 2,4,6-trichloroanisole in the stopper may be performed, for example, by measuring the area under the peak obtained at the retention time corresponding to 2,4,6-trichloroanisole, and comparison with a calibration range of compositions with known concentrations of 2,4,6-trichloroanisole.

(28) A comparative analysis by gas chromatography coupled to mass spectrometry is also performed on a gaseous sample collected in the container in accordance with the present invention, and on a control of pure 2,4,6-trichloroanisole. The mass spectrometer functions in MS/MS mode, with a chamber temperature of 45 C. and an ion trap analyzer temperature of 150 C. Identical mass spectra are obtained for the sample obtained in accordance with the invention and for the 2,4,6-trichloroanisole control, which confirms that the method according to the invention makes it possible to detect and quantify the 2,4,6-trichloroanisole present in the cork stopper. More specifically, a peak is found at 197 m/z in both spectra, corresponding to the fragmentation of the parent ion at 212 m/z of 2,4,6-trichloroanisole.

(29) The quantification of the 2,4,6-trichloroanisole content of the stopper may be performed, for example, by measuring the intensity of this peak at 197 m/z, and comparison with a calibration range of compositions with known concentrations of 2,4,6-trichloroanisole.

(30) A comparative analysis was also performed with the SPME method proposed in the prior art. To this end, ten cork stoppers were subjected to the method according to the invention, as described above. For each, the gaseous sample was analyzed by gas chromatography coupled to electron-uptake detection. The area of the peak corresponding to 2,4,6-trichloroanisole was measured.

(31) The stoppers were then recovered and were each subjected to the SPME method, according to the standard protocol described in standard ISO 20752. The 2,4,6-trichloroanisole concentration, expressed in ng/I, was measured.

(32) The results obtained for each of the stoppers, by each of the techniques, are indicated in table 1 below.

(33) TABLE-US-00001 TABLE 1 Result of the analysis of the 2,4,6-trichloroanisole content of cork stoppers, by the SPME method of the prior art and by the method according to the invention Method according to the invention (area of Stopper SPME method (ng/l) the peak) 1 0.3 0 2 0.4 0 3 1.0 9 425 4 3.5 84 429 5 3.6 83 334 6 4.8 101 827 7 6.6 145 207 8 7.7 191 720 9 11.7 306 605 10 20.4 545 914

(34) From the values thus obtained, a curve representing the area under the peak was plotted for each stopper.

(35) The values obtained for each stopper were reported on a graph, the concentration obtained via the SPME method being given on the x-axis and the area under the peak obtained in accordance with the invention being represented on the y-axis. The graph obtained is shown in FIG. 3. Perfect agreement between the values obtained via the method according to the invention and those obtained via the SPME method of the prior art is clearly seen therein.

(36) The method for analyzing a cork stopper according to the invention thus makes it possible to quantify the 2,4,6-trichloroanisole present in a cork stopper as reliably as the SPME method.

(37) It also has many advantages over the prior art methods, and especially the SPME method. It especially makes it possible to analyze up to 1440 stoppers in 24 hours for the presence of 2,4,6-trichloroanisole. It comprises few steps, which can all be performed easily, quickly and, what is more, automatically. It does not use any consumables, or reagents, such as a maceration solution or solid-phase microextraction fibers.

(38) Finally, and above all, it allows the analysis of each stopper of a batch individually, without impairing the properties of this stopper. It thus ensures that each stopper that it selects is free, or substantially free, of 2,4,6-trichloroanisole and will have no incidence on the taste and/or odor of wine conserved in the bottle that this stopper will serve to stopper.