FR2730061A1 - Gaseous phase chromatography system coupled to several detectors for pollution detection - Google Patents

Abstract

The systems sample injection unit (1) is connected by a column divider unit (6) to the input of two chromatography columns (9,10). The unit (6) permits separation of the sample into two fractions respectively introduced onto the two columns. The injection unit may be a thermal absorber or a glass separator column and the chromatographic columns are capillary columns. The output of each of the two chromatographic columns are connected to detectors (2,3,4,5) by a column divider (7,8) which permits uses of the two detectors in parallel. One of the detectors operates at reduced pressure whilst the other (s) operate at atmospheric pressure.

Description

 The present invention relates to the field of analytical techniques, specifically analytical techniques using couplings of several techniques, so-called "multicoupling" techniques.

 It relates more specifically to an improvement of the gas chromatography apparatus and its application to achieve the coupling of a chromatograph with several detectors.

 The invention is particularly applicable in the field of the analysis and quantification of volatile organic compounds, odorous or not, from a source of pollution.

Gas chromatography allows the separation of chemical compounds from a liquid or gaseous mixture through capillary or filled columns. It is therefore widely used in physicochemistry laboratories, because it ensures the identification and quantification of chemical compounds in a mixture or the determination of the degree of purity of a chemical compound. The basic apparatus comprises an injector for introducing the substance to be analyzed into a chromatographic column contained in a gas chromatograph (go). The column is connected to a detector whose nature differs according to the type of information desired. A simple coupling (GC / Detector) is then obtained. The most used are:
- GC coupling / Mass Spectrometer (MS). n essentially identifies the chemical compounds of a liquid or gaseous mixture. Quantification of these compounds is possible but imprecise compared to other detectors, flame ionization detector (FID), for example. For example, volatile chemical compounds emitted from cardboard containing orange juice have been identified by this type of coupling (JS Paik and AC Venables, J. of Chrom., 540 (1991) 456),
- GC / FID coupling. It consists of quantifying the chemical compounds previously separated from a mixture, but does not ensure their identification without having previously injected them. The examples of this coupling are very numerous,
- the coupling GC / Olfactory detector. Oct apparatus allows to inhale the compounds through a glass cone connected at the output of the chromatographic column, this to determine the odorous products. For example, D. Khiairi,
L Brenner, GA Burlingame and Suffet IH, Wat. Sci. Tech., (1992) 97, have been able to determine using the GC / FID and GC / Olfactory Detector couplings the number of odorant compounds in a drinking water sample. His analysis by
GC / MS was only able to partially identify the odorous compounds.

 In order to obtain several types of information for the same sample, series or parallel couplings of two or three detectors have been made according to the same procedure diagram: two detectors are connected in parallel at the output of a chromatographic column via a divider. This feeds the two detectors by the same gaseous sample.

The most common configurations are:
- GC / MSFlD bicoupling. This has the advantage of identifying the chemical compounds of a mixture by mass spectrometry and quantifying them by FID. This coupling exists for example in the USA at E.PA (Air and Energy
Engineering Research Laboratory) and Ispra (Joint Research Center),
- the bicoupling GC / Olfactory detector. n is used to identify FID peaks of odorous compounds in a mixture. AJ. Taylor and DS Mottram, J.

Sci. Food Agric., 50 (1990) 407, have determined odorous peaks from the oxidation of methyl arachidonate. The GC / MS coupling was used, in parallel, without success to identify these odorous compounds, since these were not detected by the mass spectrometer,
- the bicoupling GC / PID-ELCO.X / Olfactory detector. This technique uses three detectors, two of which are coupled in series (PID and ELCD: the photoionization detector (PID) detects a wide range of chemical compounds in the same way as the FID while the ELCDX, an elecho-chemical detector, detects halogens specifically. Olfactory detector was connected in parallel in order to identify the odorant compounds. This configuration was developed by T. Mamstal and JS Walker, Analyst, 117 (1992) 1361, to highlight the odorant compounds responsible for the odor odor. moldy for some pharmaceutical products,
- the bicoupling GC / MS / Olfactory detector. This configuration makes it possible to know by mass spectrometry the odorant compounds determined by olfactory detection. Eustache, J. Allois, C. Bonnefond, A. Jacquot, A. Lorant and
V. Mevel, Analusis, 16 (1988) 37, have thus identified odorous compounds derived from the air of a laboratory.

All the bicoupling analytical techniques presented above have certain drawbacks which are summarized in the table below.

<tb> Bicoipiage <SEP> used <SEP> main <SEP> disadvantages
<tb><SEP> GC / MS / FID <SEP> No <SEP><SEP> Possibility of <SEP> Determining <SEP> Odorous <SEP> Compounds <SEP>
<tb> GC / FID / Detector <SEP> Not <SEP> for <SEP> identification of <SEP> compounds <SEP> without <SEP> their <SEP> injections
<tb><SEP> Olfactory <SEP> to the <SEP> prerequisite.
<tb><SEP><SEP> Analysis Time <SEP> Doubles <SEP> in <SEP><SEP><SEP> Case <SEP> by
<tb><SEP> GC / MS
<tb> GC / MSDetector <SEP> Low <SEP><SEP> Domain of <SEP> Linearity <SEP> and
<tb><SEP> olidctif <SEP> quantification <SEP> little <SEP> accurate <SEP> compared <SEP> with <SEP> FID <SEP>
<tb> GC / PID-ELCDXI <SEP> Not <SEP> for <SEP> identification of <SEP> compounds <SEP> without <SEP> their <SEP> injections
<tb><SEP> Olfactory <SEP> Detector <SEP> at <SEP> Previous
<Tb>

 As regards the use of simple couplings, the major drawbacks are to multiply, on the one hand, the analysis times to obtain several types of information and on the other hand the sampling, which can cause problems of reproducibility. between the different samples.

 The present invention makes it possible to overcome the drawbacks of the various coupling techniques known at present and to offer, in particular, a particularly simple system making it possible, without the disadvantages mentioned above, to couple the chromatography with several detectors in particular couplings using mass spectrometry and several detectors operating at atmospheric pressure.

 The invention proposes for this purpose a multi-coupling analytical technique involving a gas chromatograph which can be connected to four detectors in parallel via two chromatographic columns.

The method consists in dividing the substance to be analyzed at most three times: at the level of the injector to introduce it in parallel on two chromatographic columns, then at the exit of these two columns which are each connected to two detectors. The GC / MS / FID / Olfactory Detector multicoupling is a direct application of this method and it has never been realized in the multicoupling methods described so far.

 Thus, the multicoupling analytical technique proposed according to the invention has the advantage of being able to associate up to four detectors in parallel, in order to collect different types of information for a single analysis.

This method thus leads to a reduction in analysis times, costs, since only one chromatograph is sufficient, and it avoids problems of reproducibility of sampling.

 More precisely according to one of its essential characteristics, the invention relates to a gas chromatography apparatus, characterized in that its sample injection unit is connected via a device called column divider to the inlet. two chromatography columns, said device for separating said sample into two fractions respectively introduced on each of the two columns.

 When such an apparatus is provided with two columns in parallel, the end of each of the two columns can be connected to two detectors in parallel, thus allowing for a single injection to have four types of complementary information on the composition of a same sample thus avoiding all the problems possibly due to the lack of reproducibility of the injection conditions when using several successive injections to analyze the same sample.

 According to another essential feature, the invention also relates to an analytical device consisting of a chromatograph provided with two chromatographic columns and whose output of each of the two columns is connected to at least one detector.

 A first advantage of the system of the invention is that it makes it possible to multiply the information intended to identify the product introduced on each of the two columns.

 Another advantage of the system of the invention is that it makes it possible to operate with chromatographic columns, either identical or different, while being assured of an immediate correlation between the information given by the two detectors situated at the end of the same chromatography column.

 A schematic example of an analytical device according to the invention is given by the diagram of FIG.

Moreover, FIGS. 2 to 5 are given with reference to the illustrative example of the invention and represent respectively:
FIG. 2: the chromatogram from the FID detector for the sample;
- Figure 3: chn> matogram from the MS detector for the sample;
FIG. 4: the chromatogram derived from the FID detector for sample R2;
- Figure 5: the chromatogram from the detector MS for sample R2.

 The diagram of FIG. 1 represents a device according to the invention comprising a chromatograph in which the injection device 1 is connected to the inlet of two chromatographic columns 9, 10 via a device 6 which makes it possible to divide the sample leaving the injector in two fractions introduced respectively into each of the two columns.

 In the device shown diagrammatically in FIG. 1, the output of each of the two columns is connected to two detectors respectively labeled 2, 3, 4 and 5 placed in parallel and connected to the outputs of the columns 9 and 10 by two column dividers respectively denoted 7. and 8.

 The chromatograph used according to the invention may be any apparatus intended for gas chromatography. The injection unit may consist of any unit conventionally used for the injection of liquid or gaseous samples into a chromatography apparatus.

By way of examples of such injection units, mention may be made of:
- the systems allowing the direct injection of a flow in a column,
- thermodesorption injection units,
injectors of the "headspace" type commonly referred to as "headspace".

 However, in the case of the analysis of samples of compounds at low concentration, it will be advantageous to choose an injection unit consisting of a thermal desorber (1D) which has the advantage of making it possible to preconcentrate the sample .

 The device used to connect the output of the injection system to the inlet of the two columns may consist of any system to ensure this connection without leakage. A divider of glass columns will advantageously be chosen.

The two columns of chromatography that can be used can be chosen from the chromatographic columns conventionally used. It will be preferable to use capillary-type columns. These columns may be identical or different.

 The outputs of the two chromatographic columns are connected to at least one detector.

 To connect the output of a column to two detectors, it will adapt to said output a device for connecting two detectors in parallel. For this purpose, a divider made of glass or steel will advantageously be used.

 One of the advantages of the analytical technique described herein is that it enables the coupling of the chromatography with a detector operating under reduced pressure and one or more detectors operating under atmospheric pressure to be carried out in a relatively simple and particularly efficient manner. It is particularly applicable in the case where the detector operating under reduced pressure is a mass spectrometer, in particular a quadrupole analyzer mass spectrometer.

 The detectors operating under atmospheric pressure that can be coupled to the chromatograph are all detectors conventionally coupled individually to gas chromatographs, for example flame ionization detectors (E; ID), photoionization detectors (PID), eledrochemical detectors. as well as olfactory detectors.

 A particular example of coupling whose implementation is particularly simple in terms of adjustments, as will be seen in the following part of the presentation is a coupling in which one of the columns is connected to a mass spectrometer and the other a flame ionization detector and an olfactory detector.

 The analytical system, described herein, thus makes it possible to perform the coupling by playing with more flexibility on the choice of two of the parameters allowing the implementation of the device of the invention, namely the diameter and the length of the columns. chromatographic, the third parameter that can be played is, as is clear from the following description, the pressure of the carrier gas at the column head.

 Indeed, the only difficulty in the implementation of the complete analytical system of the invention relates to the flow rates of vector gas of the two columns. Indeed, the vector gas pressure at the column head at the injector must be sufficient to supply the entire analytical system even at high temperature without losing too much efficiency in the separation of compounds of the mixture. In operating mode, as the GC temperature increases, the viscosity of the carrier gas increases and decreases the carrier gas flow rate in the columns. When setting up the system, the adjustment of the helium flow rates according to the temperature of the GC must be carried out in such a way as to ensure that for the chosen analysis conditions, each detector is properly supplied with carrier gas. .

 This problem is even more important when using a mass spectrometer as a detector. Indeed, this detector very used to identify the chemical compounds of an unknown mixture, operates using a primary vacuum. For a mass spectrometer having a chemical ionization source, the vacuum reached is of the order of 13.33 to 133.32 Pa. In the case of a mass spectrometer having a quadrupole type analyzer and an impact source electronic, the vacuum reached is of the order of 1.3.10-5 to 1.3.104 Pa. n therefore admits only a very low pressure at the source of ionization.

The introduction into the analytical chain of such a detector necessarily causes a preferential path at the level of the carrier gas. If the flow rate of the carrier gas is not sufficient to feed the entire system, the column connected to the mass spectrometer will be fed preferentially leaving the other without carrier gas, which may cause premature degradation of this column. Moreover, this flow rate should not be too great compared to the normal flow rate of use of the column, because not only the column loses efficiency but it may have cause problems in the operation of the mass spectrometer. For example, the flow rate The maximum permissible carrier gas for mass spectrometers having an electron impact source is about 1 cumin while the flow rate for those having a chemical ionization source is increased to 20 ml / min. For a mass spectrometer having an electronic impact source, a too high flow rate causes the secondary pump to become isolated and, therefore, the instrument switches off.

The problems can be solved by playing as is apparent from the following discussion of the only parameters that can vary, namely:
the diameter and the length of the chromatographic columns,
the pressure of the carrier gas at the top of the column.

 In addition, special attention must be paid to any leaks caused by the introduction of the different dividers of chromatographic columns. An air leak can cause a decrease in the sensitivity of the analytical system. For this purpose, the use of glass dividers is recommended.

 In practice, the only difficulty lies in the pressure to be applied at the top of the column according to the diameters and lengths of the capillary columns used and according to the different types of detectors (operating at atmospheric pressure or under vacuum). Indeed, the main difficulty of this system lies in the carrier gas supply of the two chromatographic columns. The pressures proposed below are only a starting point for the optimization of the different possible analytical systems. Tables nl and 2 give the pressure ranges used for the simple analytical couplings, that is to say between a gas chromatograph and a detector operating at atmospheric pressure or a mass spectrometer in the case where the chromatograph is equipped with capillary columns.

Thus, when using 3 or 4 detectors operating at atmospheric pressure such as the FID for example, the pressure to be applied at the top of the column depends on the characteristics of the columns used. Two cases can be considered:
- When the two capillary columns used are identical (same inner diameters and same lengths), the pressure to be applied is at the upper limit of the pressure range proposed in Table nl. For example, for two columns of 0,2 mm internal diameter and 50 m length, the applicable pressure is at least 360 kPa. The pressure is then adjusted according to the desired flow rates. The flow measurements will be made at the exit of the detectors. in normal condition of analysis,
when the two capillary columns have different characteristics both in their diameter and in their length, the pressure to be applied is in the highest pressure range corresponding to one of the two columns (null array). For example, for two columns 0.2 mm x 50 m and 0.32 mm x 50 m, the pressure to be used is in the range 235-360 kPa The initial pressure may be 280 kPa and will be adjusted according to the flow rates desired column.

Table neither
Usual pressure applied at the top of the capillary column for simple coupling

<tb><SEP> Pressure
<tb><SEP> Diameter <SEP> column <SEP> (mm) <SEP> Length <SEP> of <SEP> column <SEP> (m) <SEP> kPa
<tb><SEP> 0.2 <SEP> 12 <SEP> 85-140
<tb><SEP> 50 <SEP> 235-360
<tb><SEP> 0.32 <SEP> 12 <SEP> 29-53
<tb><SEP> 25 <SEP> 55-95
<tb><SEP> 50 <SEP> 95-160
<tb><SEP> 0.53 <SEP> 10 <SEP> 8.5-16
<tb><SEP> 30 <SEP> 24-44]
<Tb>
When one of the detectors is a mass spectrometer having, for example, a quadrupole analyzer and an electronic impact source coupled with two or three detectors operating at atmospheric pressure, reference can be made to Table 2 which contains the indicative pressures at use when coupling "simple" GC / MS with the corresponding flows in the different types of column. Under normal operating conditions, the usual carrier gas flow rate is about 1 ml / min in the mass spectrometer for a flow rate range generally between 1 and 2 cumin depending on the mass spectrometers used. The pressure at the top of the column must therefore be adjusted in such a way that the flow rate corresponds to approximately 1 caraway in the mass spectrometer.

 When the multicoupling comprises a column supplying the mass spectrometer and a second connected to two detectors operating at atmospheric pressure, the pressure at the top of the columns is limited by the pressure allowed by the mass spectrometer.

 In order not to lose too much efficiency and resolution in the separation of chemical compounds, the normal pressure of use of the capillary column connected to the mass spectrometer (table n2) will advantageously be greater than that connected to the atmospheric detectors (zero table ). This avoids placing the columns in operating limit conditions or to have the mass spectrometer having, for example, an electronic impact source in the case where the flow rates are too great. The pressure applied at the top of the column will be, firstly, that given in Table 2. The pressure will then be adjusted in such a way that the flow rate is sufficient to feed the detectors at atmospheric pressure under normal analysis conditions.

For example, a 0.2 mm x 50 m capillary column connected to the mass spectrometer may be coupled with two atmospheric detectors via a capillary column of 0.32 mm c 12 m or 25 m or 50 m. The initial pressure of vector gas at the top of the column will be chosen of the order of 204 kPa.

If one wishes to achieve, according to the method of the invention, a multicoupling with a mass spectrometer and with three detectors operating at atmospheric pressure. A column feeding the mass spectrometer at a normal operating rate greater than 1 ml / min is preferably chosen (Table 2), thus favoring the derivation to another detector at atmospheric pressure. As before, the second capillary column connected to the two detectors operating at atmospheric pressure preferably has a lower operating pressure than that connected to the atmospheric detector and the mass spectrometer (Table n-1 and 2). The resulting pressure at the top of the column is then adjusted so that the detectors are supplied with carrier gas under normal conditions of use. For example, the 0.25 mm × 30 μm capillary column can be connected to both the mass spectrometer and the detector. at atmospheric pressure and the 0.2 mm x 12 m column can be connected to both detectors at atmospheric pressure. The initial pressure of vector gas at the top of the column chosen will be of the order of 105 kPa
Table 2
Indicative pressure applied at the top of the column for GC / MS coupling

<tb><SEP> Pressure
<tb> Column diameter (mm) <SEP> Length <SEP> column <SEP> (m) <SEP> kPa <SEP> flow rate <SEP> (mVmin)
<tb><SEP> 0.1 <SEP> 10 <SEP> 262 <SEP> 0.13
<tb><SEP> 0.2 <SEP> 12 <SEP> 21 <SEP> 0.5
<tb><SEP> 25 <SEP> 83 <SEP> 0.5
<tb><SEP> 50 <SEP> 207 <SEP> 0.5
<tb><SEP> 0.25 <SEP> 30 <SEP> 103 <SEP> 1.6
<tb><SEP> 0.32 <SEP> 25 <SEP> 76 <SEP> 1.35
<tb><SEP> 50 <SEP> 34.5 <SEP> 1 <SEP>
<tb><SEP> 50 <SEP> 172 <SEP> 1.35
<tb><SEP> 0.53 <SEP> 10 <SEP> 14 <SEP> 7
<tb><SEP> 10 <SEP> 55 <SEP> 20
<tb><SEP> 50 <SEP> 165 <SEP> 30
<Tb>
The device according to the invention is applicable to all analyzes where it is necessary to cross different information from several detectors to identify and fully quantify the constituents of a mixture.

 The fields of application of the multicoupling technique concern all sectors using physicochemistry as a method of analysis namely, in particular in the field of chemistry, the fields of the environment, food, perfumes, cosmetics, the petroleum industry and the pharmaceutical industry.

 With regard to the TD / GC / MS / FID / Olfactory Detector multi-coupling, it is intended for all odor professionals in general. For example, in the field of the environment, this technique can be applied for the study of indoor or outdoor air pollution especially in sewage treatment plants. It can be used in the food industry for the analysis of volatile phases of cartons intended for foodstuffs for example, or in the oil industry, in the development of odorless essences, in the gas analysis. exhaust, in cosmetics, for example for the analysis of perfumes, creams.

 The following example is given purely by way of illustration of the invention.

Example
The analytical technique of multicoupling described in this example makes it possible to identify and quantify volatile organic compounds (VOCs) odorant or not from a source of pollution. The injection unit consists of a thermal desorber (TD) and the detectors used are three in number:
- the FID for quantification,
- the mass spectrometer consisting of an electronic impact source and a quadrupole analyzer Limited in m / z ratio at 650 th for identification,
- the olfactory detector for the detection of odorous compounds.

The two chromatographic columns used are capillary columns whose stationary phases consist of a modified siloxane polymer of 5% phenylsiloxane polarity. The first column (50m x 0.32mm x 1m) is connected to the FID and an olfactory detector and the second column (50m x 0.22mm x 1; rn) is connected to the mass spectrometer. To connect the 0.32 mm diameter capillary column to detectors
FID and olfactory, a glass divider is used. Two pieces of deactivated silica capillary columns of equal length and 0.32 mm diameter make it possible to connect this divider to the FID and olfactory detectors. In addition, another glass divider is used to connect the injector to the two capillary columns.

The gaseous sample to be analyzed is divided twice, at the level of the thermal desorber and at the level of the. The carrier gas is helium, and the pressure at the top of the columns is 0.21 MPa
The olfactory detector consists of a glass cone in which an operator inhales the compounds at the output of the chromatographic column. In addition, an air humidifier system prevents the rapid drying of the olfactory mucosa. The operator records the retention time of each odorant inhaled through an integrator.

 After analysis, the retention times of the odorous compounds determined by the operator are compared with the retention times of the chromatographic peaks obtained by the Fil), in order to identify the odorous peaks. The retention times obtained by the FID and by the mass spectrometer can not be compared because the diameters of the capillary columns are different, and gives rise to differences in retention. Nevertheless, the order of elution of the compounds does not change because the two columns have identical stationary phases. The conpondency of the FID and mass peaks can therefore be performed to identify the odorant compounds, and more generally the VOCs.

b) Application to the identification of VOCs and odorous compounds emitted from floor coverings
The methodology described above was used in a study on the characterization of air pollution sources inside buildings. As such, two samples of R1 and R2 wallcoverings were successively packaged in an environmental chamber under the realistic conditions of use (23-C, 45% relative humidity and 1 hl rate of air change). After 24 h, an air sample is taken by pumping the air from the chamber into a glass tube containing a solid adsorbent (Tenax) allowing preconcentration of VOCs emitted at very low levels.

The adsorbent tube is then placed in the multicoupler analytical chain TD / GCS / FlD / Olfactory detector in order firstly to identify and quantify the VOCs and secondly to determine the odorant compounds. The chroma toglams FID and mass reconstituted by the total ion current () obtained for these two coatings are shown respectively in Figures 2 and 3 for the sample R1 and 4 and 5 for the sample R2. n appears a similarity between the two chromatograms which makes possible the correspondence of the signals
FID / MS.

 The identification of the compounds in MS was carried out using the spectral library included in the data processing. All the compounds identified by the mass spectrometer and their concentrations, determined by the FID, are reported in Tables 3 and 4.

Table 3
Identification and quantification of VOCs emitted by R1

<tb><SEP> RI <SEP> Concentrations
<tb><SEP> 3 <SEP>
<tb><SEP> Identified <SEP> compounds <SEP> And. <SEP> ext. * <SEP> Toleq **
<tb> Formamide <SEP> 12.5
<tb> 1,2-propanediol <SEP> 24
<tb> Toluene <SEP> 1.8 <SEP> 1
<tb> soft <SEP> p-xylene <SEP> 11.8 <SEP> 12.5 <SEP>
<tb> 2-methyl-2,4-pentanediol <SEP> 20
<tb> 2-butoxyethanol <SEP> 168.2 <SEP> 58
<tb> Cumene <SEP> 15.5
<tb> 4-methylhexanol <SEP> 13
<tb><SEP> Propylbenzene <SEP> 20.2 <SEP> 22
<tb> 3-ethyltoluene <SEP> 103
<tb> 4-ethyltoluene <SEP> 41.9 <SEP> 42
<tb> 1,2,5-trimethylbenzene <SEP> 69
<tb> Phenol <SEP> 730
<tb><SEP> 1,2,4-trimethylbenzene <SEP> 290
<tb> 2-ethylbexanol <SEP> 113
<tb><SEP> 1,2,3-trimethylbenzene <SEP> 88
<tb><SEP> 1 <SEP> -methyl-2-pyrrolidinone <SEP> 641
<tb><SEP> Propyltoluene <SEP> 35
<tb><SEP> Cymene <SEP> 61
<tb><SEP> Propyltoluene <SEP> 34
<tb> Decahydronaphthalene <SEP> 24
<tb> Ethyldimethylbenzene <SEP> 34
<tb> Undecane <SEP> 75
<tb> Ethyldimethylbenzene <SEP> 29
<tb><SEP> 2-ethylhexanoic acid <SEP> 283
<tb> Tetramethylbenzene <SEP> 27
<tb> Tetramethylbenzene <SEP> 36
<tb> 2- (butoxyethoxy) ethanol <SEP> 629
<tb><SEP> 1-ethyl-1-methylbutylbenzene <SEP> 22
<tb> Undecane <SEP> 8
<tb><SEP> 1-methylheptylbenzene <SEP> 10
<tb> Tetradecane <SEP> 146
<tb> * And. ext. : External calibration ** Toleq: Toluene equivalent
Table 4
Identification and quantification of VOCs emitted by R2

<tb><SEP> R2 <SEP> Concentrations <SEP>
<tb><SEP> m3 <SEP>
<tb><SEP> Identified <SEP> compounds <SEP> And. <SEP> ext. * <SEP> Toleq **
<tb> 2-butanone <SEP> 0.7 <SEP> 3
<tb> Trichlorethylene <SEP> 24.3 <SEP> 4,5
<tb> Toluene <SEP> 6.5 <SEP> 6
<tb> 3-heptanone <SEP> 3
<tb> 3-heptanol <SEP> 9
<tb> Cyclohexanone <SEP> 402
<tb> 3-ethyltoluene <SEP> 7
<tb> 4-ethyltoluene <SEP> 2,6 <SEP> 2,5
<tb> 1,2,5-trimethylbenzene <SEP> 5
<tb> Phenol <SEP> 696
<tb> 2-ethyltoluene <SEP> 2
<tb> 1,2,4-trimethylbenzene <SEP> 21
<tb> 2-ethylhexanol <SEP> 52
<tb> 1,2,3-trimethylbenzene <SEP> 8
<tb><SEP> 2-Ethylhexanoic acid <SEP> 40.5
<tb> 2- (butoxyethoxy) ethanol <SEP> 11
<tb> 2-isopropylphenol <SEP> 85
<tb> 4-isopropylphenol <SEP> 41
<tb> 2,4-bis-isopropylphenol <SEP> 6
<tb> * And. ext. : External calibration ** Toiêq: equivalent Toluene
The concentrations in Tables 3 and 4 are calculated from the FID signal either by external calibration or equivalent toluene, ie, depending on the response factor of toluene. Since it is not possible to perform a calibration straight line for all the compounds identified because of their large number, the calculation of equivalent toluene concentrations is generally used to give an approximate value of the concentrations of compounds emitted (AT Hodgson and JM Dalsey, Interagency Protocol and Quality Assurance Plan
Agreement CPSC-IAG-90 1256, January 1991; M.-L Mattinen, J.Tuominen and K. Saarela, Ploceedings of the 6th International Air Quality Conference
Climate, Helsinki, July 1993, 2, 1993, p. 275). It is assumed that all the volatile compounds behave in the same way as toluene on the chromatographic columns. This approximation may be suitable in the case where the emitted compounds belong to the same chemical family as toluene, that is to say the aromatic hydrocarbons or in a second approximation to saturated hydrocarbons or not. A good correlation is observed between these two calculation methods for aromatics (Ethyltoluene,
Xylenes for example) (Tables 3 and 4). On the contrary, this approximation is much less verified for oxygenated or chlorinated compounds such as trichloroethylenes or 2-butoxyethanol.

In addition, the sum of these concentrations makes it possible to calculate the
TVOC (Total Volatile Organic Compound), ie the total mass per unit volume emanating from an equivalent toluene material (M. de Bortoli, H. Knopel, E. Pecchio, A Peil, L Rogora , H. Schauenburg, H. Schlitt and
H. Vissers, Env. Int., 12 (1986) 343; H. Gustafsson and B. Jonsson, Proceedings of the 6th International Conference of Air Quality and Climate, Helsinki, July 1993, 2.1993, p. 437; R. Gehrig, M. Hill, C. Zellwerger and P. Hofer, Proceedings of the 6th International Conference of Air Quality and Climate, Helsinki, July 1993, 2, 1993, p. 431; CWBayer, Pseedings ouf kills 5th Intemationnal Conference of Air
Quality and Climate, Toronto, July 1990, 3, 1990, p. 581).

 The TVOCs calculated for R1 and R2 are respectively 3.7 mg / m3 and 1.4 mg / m3. The calculation of the ratios between the sum of the equivalent toluene concentrations of the identified products and the TVOC show that 77% of the products is identified for R1 and 95% for R2, which shows that the spectral library identifies and allows to quantify by FID the majority compounds.

 The identification of odorous compounds via the olfactory detector was performed on both wallcoverings. The identification of odorant compounds, their concentrations (in mg / m3 or equivalent toluene), the indicative intensity of perceived odor of each compound (f: low, m: medium, F: high) and the odor thresholds (M. Devos, F. Patte, J. Rouault, P. Laffort and LJ Van Gemert, IRL Press, 1990) are presented in Table 5. The determination of the odorant compounds was validated by the injection of the pure compounds comparing retention times and theoretical and experimental mass spectra.

Table 5
Identification and quantification of odorous VOCs from R1 and R2 coatings

<tb> Material <SEP> Compounds <SEP> odorants <SEP> Intensity <SEP> Concentrate <SEP> Concentrate <SEP> Threshold
<tb><SEP> odor <SEP> trations <SEP> odor trations
<tb><SEP> perceived <SEP> (g / m3) <SEP> (Tol.eq) <SEP> (mg / m3)
<tb><SEP> Toluene <SEP> f <SEP> 1.8 <SEP> 1 <SEP> 10
<tb><SEP> Propylbenzene <SEP> f <SEP> 20.2 <SEP> 22
<tb> R1 <SEP> 4-ethyltoluene <SEP> f <SEP> 41.86 <SEP> 42
<tb><SEP> 1,2,4-trimethylbenzene <SEP> F <SEP> 290 <SEP> 0.776
<tb><SEP> Cymene <SEP> F <SEP> 61
<tb><SEP> Toluene <SEP> f <SEP> 6.5 <SEP> 6 <SEP> 10
<tb><SEP> 1,2,4-trimethylbenzene <SEP> f <SEP> 21 <SEP> 0.776
<tb> R2 <SEP> Cyclohexanone <SEP> F <SEP> 402 <SEP> 2.88
<tb><SEP> Phenol <SEP> F <SEP> 696 <SEQ> 0.426
<tb><SEP><SEP> 2-ethylhexanoic acid <SEP> m <SEP> 40.5
<Tb>

Claims (10)

 1. Apparatus for gas chromatography, characterized in that its sample injection unit (1) is connected via a column divider device (6) to the inlet of two chromatography columns ( 9, 10), said device (6) for separating said sample into two factions introduced respectively on each of the two columns.  2. Apparatus according to claim 1, characterized in that said injection unit consists of a thermal desorber.  3. Apparatus according to one of claims 1 or 2, characterized in that the device (6) is a separator of glass columns.  4. Apparatus according to one of claims 1 to 3, characterized in that the chromatographic columns are capillary columns.  5. Analytical device, characterized in that it consists of a chromatograph according to one of claims 1 to 4, the output of each of the two chromatographic columns is connected to at least one detector (2, 3, 4, 5 ).  6. Device according to claim 5, characterized in that at least one of the two columns is connected to two detectors (2, 3 or 4, 5) via a device (7, 8) column splitter allowing to use both detectors in parallel.  7. Device according to one of claims 5 or 6, characterized in that one of the detectors operates under reduced pressure, or the other detectors operating at atmospheric pressure.  8. Device according to claim 7, characterized in that the detector operating under reduced pressure is a mass spectrometer, in particular a quadrupole analyzer mass spectrometer.  9. Device according to one of claims 5 to 8, characterized in that one of the columns is connected to a mass spectrometer and the other to a flame ionization detector and an olfactory detector.  10. Use of an analytical device according to one of claims 5 to 9 for analyzing and quantifying volatile organic compounds, odorous or not from a source of pollution.