Nanoporous detectors of monocyclic aromatic compounds

p0001The present invention relates to nanoporous detectors monocyclic aromatic compounds and their applications.

p0002Monocyclic aromatic compounds are toxic air pollutants for most and even carcinogen benzene. They are found in environments such as the petrochemical industry, in the chemical industry (solvent use) in environments close to industrial facilities, in professional circles (research laboratories, analytical laboratories, etc.) in fuels cars and in ambient air (evaporation of fuels, incomplete combustion of fossil fuels, smoking, use of cleaning products or for DIY).

p0003For air pollution monitoring problems in polluted atmospheres or surveillance of workers directly exposed to these compounds, it is necessary to detect and quantify the most volatile aromatic, commonly called BTEXMs (Benzene, Toluene, Ethylbenzene, Xylenes (ortho , meta and para), trimethyl (1,2,3; 1,2,4 and 1,3,5) benzenes).

p0004Measurements of monocyclic aromatic hydrocarbons (HAM) are usually made in ambient and indoor air:

p0005These measurements are made in two distinct stages: collection and analysis. On workplaces is carried out two types of measurement: either the staff or individual exposure measurement atmosphere around a fixed point of work. Sampling can be either active (pumping air through a silica cartridge covered with a stationary phase) or passive (diffusion through the same cartridge without pumping). The analysis is in both cases performed offline in the laboratory.

p0006For samples followed by in situ analysis, there are continuous analyzer. portable micro-chromatographs include operating autonomously (sampling, concentration, analysis). However, they are bulky and require the use of various gases, nitrogen, air and hydrogen with a FID detector (flame ionization detector) or nitrogen with a PID detector (photoionization detector), the latter being limited to concentrations below 300 ppbv<i>(Part per billion volume</i> or parts per billion by volume).

p0007To meet the demand for direct measurement sensors, many researchers have tried to develop chemical sensors BTEXMs with good selectivity.

p0008The difficulty of finding specific probe molecules for these compounds is that they are virtually non-polar (dipole moments between 0 and 0.3 Debye). The BTEXMs can therefore only weakly interact with other molecules by forces of dispersion or electrostatic forces at short range. The detection principles reported in the literature are essentially based on these non-selective weak interactions and selectivity testing by the size. aromatic macrocycles that purpose is used, sensitive fluorophores microscopic environment such as Nile Red and semiconductor-based sensors and mixed oxides. For selectivity by size, cage molecules whose cavity is cut to accommodate the target pollutant (eg paracycolphanes, calixarenes or cyclodextrins), have been proposed, but these systems are not selective.

p0009Also known detectors benzene based porous matrices of organic-inorganic hybrid polymers based on silicon alkoxides (Si (OR)_notR_4-n with R = CH₃). With thick matrices may vary between 500 microns and 2 mm, and having nanopores of radius between 3.5 and 9 a.<nplcit id="ncit0001" npl-type="s"><text>Calvo-Muñoz et al. ( "Chemical sensors of Monocyclic aromatic hydrocarbons based on sol-gel materials: kinetics of trapping pollutants and of the sensitivity of the sensor", Sensors and Actuators B, vol 87, pp 173-183..), 2002</text></nplcit>) Have shown that it is possible to entrap almost irreversibly benzene and toluene and discriminate by their absorption spectrum. With monolithic blocks of 2 mm thick, the sensitivity obtained in the laboratory for benzene and toluene is 10 ppbv and this for an exposure of 2 hours at a flow rate of 20 mL · min^-1. For higher exposure rates of 250 mL · min^-160 ppbv can be measured in an exposure time of 14 minutes. Benzene trapping efficiency and toluene in these matrices is 100% for low concentrations (<10 ppbv) and low-speed (20 mL · min^-1) But strongly decreases (5-6%) when the concentration is> 1 ppmv (<i>vpm</i> or parts per million by volume) and the flow rate is> 50 mL.min^-1. In all cases, the trapping is almost irreversible. Ortho-xylene and meta-xylene and trimethylbenzenes, can not diffuse into these materials whose pores are too small (diameter <20Å), making it selective detectors for benzene, toluene and para-xylene only. While the trapping and measurement are performed in a single step, trapping the pollutants is however irreversible.

p0010Since 2001, the firm NTT (Nippon Telegraph &amp; Telephone Corp.) is working on various porous adsorbents diameter of silica cubic from about 2 micrometers with pores of controlled sizes, which serve to trap BTEMXs. See for example Y. Ueno, A. Tate, and O. Niwa "Benzene sensor and method for manufacturing same", Patent<patcit id="pcit0001" dnum="EP1712889A1"><text>EP1712889A1, 18 October 2006</text></patcit>. Cubes fill a microfluidic flow chamber provided with a heater (electric resistance engraved on the rear side) which serve to thermal desorption of pollutants. During pre-concentration step, the air containing the pollutants is pumped through the flow chamber for a period of about ten minutes to 1 hour 30 minutes depending on the content of pollutants. These are partially trapped in the porous material. The chamber is then heated to 200 ° C for 10 seconds to desorb the contaminants. The gas is transferred by a second pump in an optical chamber (quartz cell 2cm or optical fiber 12 cm) and are detected using their absorbance using a UV spectrophotometer (Soma Optics Fastevert S-2400) . Selectivity is achieved by spectral deconvolution from a spectral database of various BTEMXs. All capture and detection device is included in a ventilated case dimensions 37,5x20x16 cm weighing 6.7 kg, not included computer. Detector sensitivity is 1 ppbv for 90 min exposure, 50 ppbv for 50 minutes of exposure. The detector is relatively insensitive to the relative humidity of air between 40 and 80% relative humidity.

p0011The apparatus of NTT firm has the required criteria in terms of sensitivity and speed but the device still involves two stages, the pre-concentration and analysis. In this case, a heating system with a fast ramp temperature is necessary to expel pollutants trapped in these matrices and transfer them into the analysis chamber.

p0012<patcit id="pcit0002" dnum="US2003180964A1"><text>US 2003/180964 A1</text></patcit> describes a sol-gel material porous in nature consisting essentially of units derived from tetramethoxysilane (TMOS) and units derived from 3-aminopropyltrimethoxysilane (APTMS), in a molar ratio polyalkoxysilane first / second polyalkoxysilane of 1 / 0.011.

p0013<patcit id="pcit0003" dnum="WO2006094392A1"><text>WO 2006/094392 A1</text></patcit> describes a sol-gel material consisting essentially of units derived from tetraethoxysilane (TEOS) and units derived from APTMS. The sol-gel process of Example 4 implements a triblock copolymer which is washed after the material preparation suggesting that the resulting material would be of a porous nature.

p0014<patcit id="pcit0004" dnum="US4017528A"><text>US 4017528 A</text></patcit> discloses a porous sol-gel material consisting essentially of units derived from TEOS and units derived from 3-aminopropyltriethoxysilane (APTES) in a molar ratio polyalkoxysilane first / second polyalkoxysilane from about 1 / 0.58.

p0015<patcit id="pcit0005" dnum="US6667016B1"><text>US 6 667016 B1</text></patcit> discloses a porous sol-gel material consisting essentially of units derived from tetramethoxysilane (TMOS) and units derived from (N- (3- (trimethoxysilyl) propyl) ethylenediamine, in a molar ratio polyalkoxysilane first / second polyalkoxysilane of 1 / 0.2 .

p0016<patcit id="pcit0006" dnum="US2003231984A1"><text>US 2003/231984 A1</text></patcit> discloses a consisting essentially of units derived material tetramethoxysilane (TMOS) and units derived from 3-aminopropyltriethoxysilane (APTES), in a molar ratio polyalkoxysilane first / second polyalkoxysilane from about 1 / 0.03. According to Example 3 said material is obtained by a sol-gel process and is of a porous nature.

p0017<nplcit id="ncit0002" npl-type="b"><text>Kunzelmann et al: "Biosensor properties of glucose oxidase immobilized Within SiO2 gels" sensors and actuators B, ELSEVIER SEQUOIA SA, Lausanne, CH, vol. 39, no. 1-3, 1 March 1997 (1997-03-01), pages 222-228</text></nplcit> describes a sol-gel material consisting essentially of units derived from TEOS and units derived from APTMS, in a molar ratio polyalkoxysilane first / second polyalkoxysilane from about 1 / 0.33, said material being a xerogel.

p0018The review of analyzers marketed or proposed in the literature, it appears that there is demand devices for trapping and measuring the mononuclear aromatic hydrocarbons (HAM) in one step while preserving the reversible nature of the process. Preferably one would use a single chamber for exposure to HAMs and measurement. It would also be desirable to carry out the desorption of gas without using a heater.

p0019The sensor embodiment of steps should be as short as possible, for example less than 24 hours.

p0020The size and the sensor manufacturing cost should be reduced more.

p0021The sensor material should allow rapid diffusion of pollutants and show a good return trapping HAMs.

p0022Trapping should be reversible.

p0023The detection system using such sensors should be miniaturized while keeping a good signal / noise ratio.

p0024For measurements on a workplace, it would also be desirable that a detection system has good battery life, at least 8h for example, which corresponds to one day of work and it is robust, low size, easily portable by an individual and is therefore lighter.

p0025Now, after extensive research we have discovered a versatile detector BTEMXs and their common solvents, based on the use of new porous materials, satisfactory.

p0026This is why this application is for <i>a trapping process of monocyclic aromatic hydrocarbons using as sensor</i> a porous sol-gel material consisting essentially of<ul><li>of units of one or more first (s) polyalkoxysilane (s) chosen (s) from the following compounds: (chloromethyl) triethoxysilane; 1,3-diméthyltetraméthoxydisiloxane; ethyltrimethoxysilane; triethoxy (ethyl) silane; the triéthoxyméthylsilane; triethoxy (vinyl) silane; trimethoxymethylsilane; trimethoxy (vinyl) silane; tetraethoxysilane or tetramethoxysilane and advantageously one polyalkoxysilane and more particularly tetramethoxysilane (TMOS) and</li><li>of units of one or more second (s) polyalkoxysilane (s) chosen (s) from the following compounds: (N- (3- (trimethoxysilyl) propyl) ethylenediamine, 3-aminopropyltriethoxysilane (APTES) and 3- aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane advantageously, in a first molar ratio (s) polyalkoxysilane (s) / second (s) polyalkoxysilane of 1 / 0.01 to 1/1, <i>wherein contacting a stream may contain monocyclic aromatic hydrocarbons with the sol-gel material, optionally incorporating a probe molecule, or circulates such a flow thereon. The first molar ratio (s) polyalkoxysilane (s)</i> / <i>second (s) is polyalkoxysilane</i> preferably from 1 / 0.01 to 1 / 0.50, in particular from 1 / 0.01 to 1 / 0.30, preferably from 1 / 0.01 to 1 / 0.15, in particular of 1/0, 02-1 / 0.06; preferably the first polyalkoxysilane is TMOS.</li></ul>

p0027It should be noted that the (N- (3- (trimethoxysilyl) propyl) ethylenediamine, 3-aminopropyltriethoxysilane (APTES) and 3-aminopropyltrimethoxysilane comprise at least one primary amine function.

p0028(S) first (s) polyalkoxysilane (s) is (are) chosen especially (s) from compounds include: methyltrimethoxysilane, tétraéethoxysilane, methyltriethoxysilane and tetramethoxysilane (TMOS).

p0029Preferably the porous sol-gel material is essentially composed of units of one or more first (s) polyalkoxysilane (s) and of units of one second polyalkoxysilane, and particularly of units of a single first polyalkoxysilane and units of one second polyalkoxysilane.

p0030The sol-gel material <i>used may</i> be prepared essentially from one or more first (s) polyalkoxysilane (s) selected (s) from the following compounds: (chloromethyl) triethoxysilane; 1,3-diméthyltetraméthoxydisiloxane; -ethyltrimethoxysilane; triethoxy (ethyl) silane; triéthoxyméthylsilane; triethoxy (vinyl) silane; trimethoxymethylsilane; trimethoxy (vinyl) silane; tetraethoxysilane or tetramethoxysilane and advantageously one polyalkoxysilane and more particularly tetramethoxysilane (TMOS) and units of one or more second (s) polyalkoxysilane (s) chosen (s) from the following compounds: (N- (3- (trimethoxysilyl ) propyl) ethylenediamine, 3-aminopropyltriethoxysilane (APTES) and 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane advantageously, in a first molar ratio (s) polyalkoxysilane (s) / second (s) polyalkoxysilane (s) of 1 / 0.01 to 1/1, preferably 1 / 0.01 to 1 / 0.50, in particular from 1 / 0.01 to 1 / 0.30, preferably from 1 / 0.01 to 1 / 0.15, in particular of 1 / 0.02 to 1 / 0.06, preferably the first polyalkoxysilane is TMOS.

p0031Preferred are porous sol-gel materials can be prepared essentially from one or more first (s) polyalkoxysilane (s) and one second polyalkoxysilane, and especially on one polyalkoxysilane first and one second polyalkoxysilane .

p0032Preparation methods are described below.

p0033The sol-gel material of the invention is porous and has a pore size distribution ranging from 10 to 60 Angstroms, particularly 20 to 60 Angstroms and a surface area of ​​200 to 800 m².g^-1. Preferably, the specific surface is 650 ± 70 m².g^-1.

p0034Among the latter polyalkoxysilanes included in the composition of the material, preferred is 3-aminopropyltriethoxysilane (APTES).

p0035Particularly preferred sol-gel materials are prepared primarily from tetramethoxysilane (TMOS) and 3-aminopropyltriethoxysilane (APTES) in a molar ratio of TMOS / APTES 1 / 0.01 to 1 / 0.30, preferably from 1 / 0.01 to 1 / 0.15, preferably from 1 / 0.01 to 1 / 0.10, in particular from 1 / 0.02 to 1 / 0.06, most preferably from 1 / 0.03 and therefore comprise units of one and the other (s) in such proportions.

p0036To recall, a sol-gel material is a material obtained by a sol-gel method using as precursors of alkoxides of the formula M (OR)_not wherein M is a metal, especially silicon, and R an alkyl group, and hydrolyzing them. In the presence of water, hydrolysis of the alkoxy groups (OR) occurs, forming small particle size generally less than 1 nanometer. These particles aggregate and form clumps that remain in suspension without precipitate and form a floor. The increase in mass increases the viscosity of the medium which gels. A sol-gel material is obtained by drying the gel, by removing the solvent out of the polymer network formed.

p0037The sol-gel material of the invention comprises units and is prepared essentially from 2 to 4 polyalkoxysilanes, especially 2 or 3 and especially 2 polyalkoxysilanes. The final material may contain 50 to 95% derivatives of polyalkoxysilanes.

p0038Structuring compounds (organic polymers, neutral surfactants, anionic surfactants, cationic surfactants, etc.), allowing to obtain a uniform porous structure and / or forms of specific cavity may be added to the soil departure provided that they can be removed by washing or calcination without damaging the optical and structural properties of the matrix.

p0039A sol-gel material above may incorporate a probe molecule.

p0040Whether accurate or not, in what follows, the term "sol gel material" denotes a sol-gel material alone a sol-gel material incorporating a probe molecule, unless the context shows that is one of them and not the other.

p0041A probe molecule is a molecule adapted to compounds or pollutants to trap or to detect or detect and trap, with which it can react and can be for example 4-amino-3-penten-2-one (Fluoral-P® ) for the detection of formaldehyde. The incorporation of a probe molecule used to expand the range of compounds or pollutants covered by the invention.

p0042Preferred probe molecules are hydralazine for the detection of acetaldehyde, and crotonaldehyde hexaldehyde; 2,4-dinitrophenylhydrazine for the detection of aldehydes and ketones in their entirety; 4-amino-3-penten-2-one (Fluoral-P) for the detection of formaldehyde, iodine oxides (KIO₄, I₂O₄ and I₂O₅) For the aromatics or alkanes, a triphenylmethane derivative (bromothymol blue, bromophenol blue, bromocresol green, cresol red, phenolphthalein, Malachite Green, etc.) or a derivative of azobenzene (methyl orange, red congo, methyl red, methyl yellow, alizarin yellow R, etc.) for the detection of carboxylic acids

p0043The weight percentage of probe molecules is preferably 0.1 to 40%, preferably 10 to 40% and most preferably from 10 to 30% based on the total weight of the material.

p0044A process for preparing the sol-gel material is characterized in that one mixes the (s) first (s) polyalkoxysilane (s), PREFERABLY e tetramethoxysilane with one of its organic solvents miscible with water is added then (s) second (s) polyalkoxysilane (s) is added water, plus, if desired, a catalyst or a structuring agent, or both, and stirring is continued to obtain the ground and then freezing. If desired, the soil is placed in molds to obtain blocks of the gel. In combination, the molecules of tetramethoxysilane and second (s) polyalkoxysilane (s) are called "unit (s)."

p0045Preferably mixed at a temperature between -45 and + 30 ° C or the first (s) polyalkoxysilane (s) with one of their organic solvents miscible with water, is then added or the second (s) polyalkoxysilane (s), is added water, plus, if desired, a catalyst or a structuring agent, or both, and preferably only one structuring agent, and the stirring is continued to obtain the ground then the expected sol-gel, according to an advantageous embodiment, placing the soil in molds to obtain blocks of the expected sol-gel.

p0046Note that in the present application, conventionally the indefinite article "a" must be considered as a generic plural (meaning "at least one" or "one or more"), unless the context shows otherwise (1 or "one"). Thus, for example, when it is said above that one adds a structuring agent, it is the addition of one or more structuring agents or when it is said that there is incorporated a molecule -sonde, it is one or more probe molecules.

p0047Under preferential conditions for implementing the process described above is mixed (s) first (s) polyalkoxysilane (s), preferably tetramethoxysilane (TMOS) with its organic solvents which is particularly acetone, formamide, methyl ethyl ketone, chloroform, dichloromethane, acetic acid, methanol, ethanol, propanol, butanol, pentanol, hexanol and preferably an alcohol such an alkanol C₁-C₅, Preferably C₁-C₃ and in particular methanol.

p0048The mixture may be carried out at a temperature between -45 and + 30 ° C and preferably between -25 and -15 ° C, for a period of between 1 and 10 minutes and preferably from 2 to 3 minutes. Preferably mixing is carried out at a temperature between -25 and -15 ° C, for a period of between 2 and 3 minutes.

p0049is then added (s) second (s) polyalkoxysilane (s) and especially the 3- (aminopropyl) triethoxysilane, preferably in a proportion lower than or equal to the first. Stirring is continued for a period of usually 1 to 10 minutes and preferably 2 to 3 minutes. Finally, the added water is preferably ultrapure, plus, as required, the catalyst and / or structuring agent, and preferably only of a structuring agent. Stirring is then maintained even 10 to 120 seconds and more particularly for 40 to 60 seconds.

p0050Preferably all the synthetic steps above are performed at low temperature.

p0051The molar ratio polyalkoxysilanes / solvent / water is preferably from 1/4/1 to 1/100/30, particularly 1/4/4 and particularly 1/5/4.

p0052Use is advantageously made of polystyrene or polypropylene as a constituent material of the molds to obtain blocks of desired gel.

p0053In other preferential conditions of implementation of the method described above, further drying is carried out blocks of the sol-gel to evaporate the residual solvent. Drying the sol-gel matrices advantageously takes place at a controlled temperature and under an atmosphere of dry inert gas (nitrogen, argon, air, etc.). Drying the sol-gel blocks may in particular be carried out by using a gas permeable lid and more particularly to a porous film on the surface of the molds and placing the molds in a chamber thermostated at a temperature between 25 and 60 ° C and more particularly at 45 ° C in the case of a material not incorporating a probe molecules and at 25 ° C in the contrary case. The drying atmosphere is preferably a clean dry inert gas (nitrogen U quality, industrial quality air FID, etc.). The time for complete drying will vary from 2 hours to 10 days and in the preferred case about 2 hours for a volume of about 2 or block particular 5.10^-3 cm³.

p0054In the case where the material contains one or more surfactants, these are removed either by washing or soaking in an aqueous or organic solution or by calcination after gelation.

p0055The present application also relates to a process for preparing a sol-gel material incorporating a probe molecule able to selectively react with a target compound. The incorporation of this or these probe molecules can be done in several ways.<ul><li>the "one-pot" method, which is preferred, which comprises adding the probe molecule directly in the preparation of the soil. In this case, the probe molecule is directly encapsulated in the silica network. Dilution or dissolution of probe molecules can make the choice in the solvent or water used to prepare the ground. The preferred choice is to dilute or dissolve the probe molecule in the environment where it is most soluble or miscible better.</li></ul><ul><li>The method by using a gas diffusion or liquid process comprises contacting the probe molecule in the empty pores of the sol-gel material after drying. In this case, the probe molecules are adsorbed to the material surface or linked to the surface by non-covalent bonds (hydrogen bonds or ionic bonds). The method by using a gas diffusion involves contacting the probe molecules in a gaseous form directly with the material (under partial vacuum or gas flow). The method using a liquid diffusion consists in bringing the sol-gel material directly into a solution (aqueous or solvent) containing dissolved or diluted probe molecule.</li><li>The method by functionalizing or post-doping of creating a covalent bond between the sol-gel material and the probe molecule. For this, it is advantageous to functionalize the surface of the sol-gel material to improve its compatibility with the probe molecule or functionalize it.</li></ul>

p0056As noted, one can incorporate two or more probe molecules.

p0057Sol-gel materials object of the present invention have very advantageous properties and qualities. They are endowed with particularly outstanding scavenging properties of a variety of common solvents and monocyclic aromatic hydrocarbons including benzene, toluene, xylenes, mesitylene and styrene.

p0058They are also transparent in the UV, thereby directly measuring the absorbance of monocyclic aromatic hydrocarbons trapped, these hydrocarbons are generally distinguished by their UV absorbance.

p0059Sol-gel materials object of the present invention can be used with monocyclic aromatic hydrocarbons including gaseous form.

p0060More generally, the sol-gel materials of the invention can trap compounds which absorb in the UV-visible with a molar extinction coefficient greater than 250 M^-1cm^-1. Sensitivity is suitable for concentrations ≥1 ppmv and even a dozen ppbv for gases with a high absorption coefficient as styrene.

p0061They make possible the detection of BTEMXs by an absorbance measurement. In some cases as the case of styrene, the metrology of the pollutant can be implemented by means of fluorescence measurements.

p0062Used on a thin, for example from 100 to 800 microns and preferably 100 to 500 .mu.m, they allow reversible trapping HAMs and their common solvents.

p0063Using a spectrophotometer, advantageously miniaturized and cooled, allows detection by measurement of absorbance or fluorescence is excellent and sensitive.

p0064Compared to porous adsorbents cubic silica, one can note in particular the following advantages:<ul><li>trapping and measurement are possible in a single step;</li><li>one room is used for exposure and measurement;</li><li>gas desorption can be performed without heating by use of a sensor system adapted to millifluidic.</li></ul>

p0065Thanks to the use of two distinct groups of polyalkoxysilanes, first (s) and second (s) polyalkoxysilanes as defined above, based on porous matrices based on benzene adsorbents of organic-inorganic hybrid polymers based on silicon alkoxides (Si (OR)_notR_4-n with R = CH₃), One can note in particular the following advantages:<ul><li>synthetic steps and drying the porous sensors are reduced to 4 hours instead of 2 months;</li><li>the sensor size is reduced and the cost of manufacture; </li><li>the new porous material allows faster diffusion of target compounds;</li><li>millifluidic the system increases the trapping efficiency;</li><li>trapping is reversible and target compounds are desorbed without heating;</li><li>the detection system can be miniaturized and the signal / noise ratio is improved.</li></ul>

p0066Moreover, the sol-gel material obtained by the process of the present invention allow a long range of 300 to 400 measurements, which correspond to 3 to 4 days if a measurement is performed every fifteen minutes. This autonomy can be increased to 6-8 days if the measurement rate is equal to 30 minutes and even more if the measurement rate decreases; Moreover, trapping devices and / or detection systems implementing them are robust, compact, portable and lightweight.

p0067Sol-gel material obtained by the process of the present invention have the property of having an intrinsic pH close to 7. Through the use of the various above-mentioned amino polyalkoxides, it is possible to change the intrinsic pH of the material without having using the addition of a base (OH^-). PH values ​​between 7 and 8.2. In the aforesaid preferred cases, the pH is 7.5 ± 0.3.

p0068When incorporating a probe molecule, the matrices may selectively trap a variety of compounds with a specific reaction between the probe molecule and the target compound. In this case, trapping the analyte (target compound) is irreversible. then one can quantitatively measure the target compound trapped by detecting the product of the interaction or reaction thereof with the probe molecule. Other target compounds present in the medium at the time of analysis may also be entrapped in this case but are not detected in the absence of specific reaction. In other cases, the probe molecules are sensitive to low pH variations due to the trapping of an acid target compound, which interacts via weak bonds with the probe molecule. The reaction is reversible in this case.

p0069These properties are illustrated below in the experimental part. They justify the use of soil materials gels described above, as well as soil materials gels incorporating a probe molecule, in the trapping of monocyclic aromatic hydrocarbons, as well as other target compounds and / or detection.

p0070This is why the present application relates to a process for trapping of monocyclic aromatic hydrocarbons using as a sensor a sol-gel material described above, wherein there is contacted a flow likely to contain monocyclic aromatic hydrocarbons or other target molecules with a sol-gel material described above, optionally incorporating a probe molecule, or circulates such a flow thereon.

p0071The stream may contain monocyclic aromatic hydrocarbons can come from a polluted atmosphere. It can travel at October 1 mL · min flow^-1 1.1 L.min^-1.

p0072A process for preparing a sol-gel material incorporating a molecule above probe, is characterized in that is added to the sol-gel material a probe molecule either directly during the preparation of the soil of the sol-gel material or diffusion of this probe molecule in said material by diffusion by gas or by liquid method.

p0073A process for preparing a sol-gel material incorporating one or more probe molecules above cited (s), is characterized in that is added to the sol-gel material at a low temperature of -45 to 15 ° C or the molecule (s) -sonde either directly during the preparation of the soil of the sol-gel material or by diffusion of this or these molecule (s) -sonde (s) in said material by diffusion by gas or by liquid method. The sol-gel material has an intrinsic pH close to 7, which can be varied in a pH range of 7 to 8.2, and for example in the case where the unit of first alkoxysilane is TMOS and unit second polyalkoxysilane is APTES, by increasing the proportion of APTES with respect to TMOS.

p0074In addition to trapping monocyclic aromatic hydrocarbons, can also be detected and / or assaying them. To this end, one can proceed also in their trapping.

p0075The present application therefore also relates to a method above further wherein, one proceeds to the detection of monocyclic aromatic hydrocarbons and their common solvents trapped in sol-gel materials above, optionally incorporating a probe molecule.

p0076The detection can be carried out in particular by optical measurements, mass, or acoustic.

p0077When the detection is performed by optical measurement, the wavelength is preferably selected for which the absorbance of the target compound is highest. One can also choose the wavelength for which the fluorescence of the target compound is highest.

p0078To assay the monocyclic aromatic hydrocarbons trapped on the sol-gel materials above, optionally incorporating a probe molecule, mention may perform a measurement of the change in absorbance, fluorescence, luminescence, mass, or resonance frequency of the monolith when exposed to a stream containing the (or the) target compound. The measurement obtained compared with the measurement obtained from calibrated flow target compound directly provides information on the amount and / or nature of the target compound in the exposure stream.

p0079As noted above, when they incorporate a probe molecule, the above sol-gel materials can trap a variety of target compounds as the monocyclic aromatic compounds, aldehydes, alkanes, carboxylic acids , ketones and chlorine, in particular monocyclic aromatic compounds, aldehydes, alkanes, carboxylic acids and ketones.

p0080This is why the present application also relates to a target compounds of entrapment method selected from monocyclic aromatic compounds, using as a sensor a sol-gel material described above incorporating a probe molecule, wherein contacting a flow may contain a target compound from those mentioned above with said sol-gel material described above incorporating a probe molecule, or is circulated as a flux thereon.

p0081The stream can be any gas that may contain these compounds target that can come from a polluted atmosphere. The gas stream can flow at a rate of 10 mL · min^-1 1.1 L.min^-1.

p0082In addition to trapping the target compounds, can also be detected and / or assaying them. To this end, one can proceed also in their trapping.

p0083The present application therefore also relates to a method above further wherein, one proceeds to the detection of target compounds trapped on the above sol-gel materials incorporating a probe molecule.

p0084The detection can be carried out in particular by optical measurements, mass, or acoustic.

p0085When the detection is performed by optical measurement, is preferably chosen wave length for which the absorbance, fluorescence or luminescence of the probe molecule, or the product formed by the interaction or reaction between the molecule- probe and the target compound is highest.

p0086To assay the target compounds trapped on the sol-gel materials above incorporating a probe molecule, mention may in particular be at choice changes in absorbance or fluorescence or luminescence of the probe molecule over time or changes absorbance or fluorescence or luminescence of the product of the reaction between the probe molecule and the target pollutant-over time. In both cases the results will be compared to results obtained in the same exposure conditions with calibrated flow of target compounds.

p0087The present application also relates to a system for trapping of monocyclic aromatic hydrocarbons using as a sensor a sol-gel material described above, optionally incorporating a probe molecule. Such a sensor typically comprises a sol-gel material block described above reproducible shape, for example parallelepiped, cylindrical, cubic, trapezoidal, etc., lower surface or equal to 150 mm², And preferably less than or equal to 100 mm², And less than or equal to 2 mm thickness. This sensor is typically used in a cell consisting essentially of:<ul><li>millifluidic a system for the gas flow and in which is inserted a sol-gel material described above;</li><li>an exposure chamber provided with optical windows and openings for the millifluidic system (gas inlet and outlet);</li></ul>

p0088In the present disclosure, the term "millifluidic system" means a system allowing the passage of a gas flow rate 10 mL · min^-1 1.1 L.min^-1, Preferably 100 mL.min^-1 for the trapping step.

p0089The present application is equally relates to an aromatic monocyclic detection system and their common solvents using as a sensor a sol-gel material described above, optionally incorporating a probe molecule. Such a detection system typically comprises<ul><li>above an exposure chamber;</li><li>a system millifluidic above;</li><li>a collimating optical system and focusing light analysis;</li><li>optical fibers for conveying light;</li><li>a (micro) pump adapted to the desired flow rate;</li><li>a spectrophotometer or other sensing device.</li></ul>

p0090The detection system can be used in particular as follows:

p0091The sol-gel material block is inserted into the millifluidic system. The latter is placed in the exposure chamber. Is circulated mixture of gaseous compounds in the target millifluidic system for a short time (15 sec to 2 min). During the exposure time, the sensor of the absorption spectrum is collected every second in the manner described below. The analysis light from a UV lamp (deuterium) is conveyed with the aid of an optical fiber illuminates continuously from the chamber entrance window. The light beam, collimated with a lens (focal length = 10 mm) and an SMA connector on the input window, the sensor illuminates a small area, for example 1 mm². The transmitted light is collected in the same axis via a second lens and a second SMA connector on the output of the bedroom window. The transmitted light beam is conveyed by means of an optical fiber to an optionally miniature spectrophotometer. A sensor of the absorption spectrum is collected every seconds during each acquisition of 8-1000 msec (preferably 20 msec).

p0092When the acquisition is complete, we can free the trapped target compounds and purge the sensor. One can for this purpose expose the sensor to a 4 airflow L.min^-1 for about 5 minutes.

p0093The absorbance signal of the sensor exposed for each target compound is acquired over a wide range of concentration of the target compound and a wide range of relative humidity of the gas mixture. From these data, calibration curves are prepared for each target compound depending on its concentration and humidity of the gas mixture. These calibration curves are stored in a database which will be used in spectral deconvolution of a spectrum of the sensor exposed to an unknown mixture of gaseous target compounds.

p0094The absorbance signal is deconvoluted from a database of the absorption spectra of each of the target compounds previously determined in such a matrix as described above.

p0095For the salting step, the flow rate of the gas stream can vary from 2 L.min^-1 5 L.min^-1 and is preferably set at 4 L · min^-1.

p0096In the case of a doped matrix of probe molecules capable of reacting with the target compounds, the reaction between the probe molecule and the target compound is in most cases irreversible. The purging step is not carried out to achieve a salting but to purge the fluid circuit of the compounds present in the gas mixture and unreacted with the probe molecules. In this case, the flow rate of the purge stream is advantageously set to a value of 10 mL · min^-1 1.1 L.min^-1.

p0097In the case of a sol-gel material containing one or more probe molecules derived either triphenylmethane is azobenzene, purging is advantageously carried out by changing the pH conditions of the stream, or to sol-gel material observe a return to the conditions of initial optical measurements.

p0098Moreover, when the fluid circuit operates continuously (or loop) through a circulation pump for a sufficiently long time (a few seconds to 1 hour) during which the target compounds enter into the matrix and react with molécules- probe, optical measurements are carried out (collecting absorption spectra or fluorescence) at preferably regular intervals (1 to 300 seconds) during that period.

p0099The examples which follow illustrate the present application and the invention will be better understood if reference is made to the accompanying drawings in which<ul><li>the <figref idrefs="f0001">figure 1</figref> shows a schematic view of the measuring device in its entirety (measuring cell, spectrophotometer, deuterium lamp, pump);</li><li>the <figref idrefs="f0001">2</figref> represents a perspective view of a copper plate for forming the millifluidic system;</li><li>the <figref idrefs="f0002">3</figref> shows a cross sectional view of an exposure chamber;</li><li>the <figref idrefs="f0002 f0003">4</figref> represents the absorbance readings of p-xylene as a function of wavelength; for a sensor exposed to a nitrogen stream containing 11.86 ppmv of p-xylene, where the<figref idrefs="f0002">4a</figref> represents the evolution of the absorption spectra during the trapping of a target compound and <figref idrefs="f0003">4b</figref> represents the change of the absorption spectrum of a matrix during the release (matrix purge in the case of a simple trapping of the target compound by physical adsorption);</li><li>the <figref idrefs="f0003">5</figref> represents a series of exposures of a sol-gel block to gas mixtures followed by purging the sol-gel block. Each "pulse" corresponds to a linear increase in absorbance for one minute of exposure to a target compound, followed by an exponential decrease in absorbance for 5 minutes while purging. The value of the slope of the absorbance of growth signal is characteristic of the concentration of target compound in the exposure stream;</li><li>the <figref idrefs="f0004">6</figref> represents a recorded spectrum upon exposure to a mixture of target compounds (benzene, para-xylene and mesitylene). The spectrum corresponds to the sum of the spectra of the target individual compounds under the same conditions;</li><li>the <figref idrefs="f0004">7a</figref> shows the fluorescence spectra recorded during exposure of a sol-gel doped block of probe molecules (here Fluoral-P) to a gas flow of 200 ml.min-1 containing 10 ppbV formaldehyde. The spectral variations over time correspond to an increase of the fluorescence of the product resulting from the reaction between Fluoral-P and formaldehyde (excitation wavelength = 405nm - excitation time = 2 seconds).</li><li>the <figref idrefs="f0005">7b</figref> represents the changes in the fluorescence range (between 470 and 750 nm) of a hand (solid line curve) and the fluorescence maximum at 520 nm (dashed curve) on the other hand, during the exposure of a doped matrix Fluoral-P at a flow 200mL.min-1 containing formaldehyde 10 ppbv. The slope at the origin of these two curves is characteristic of the formaldehyde concentration of the exposure flow.</li><li>the <figref idrefs="f0005">8a</figref> shows the absorption spectra taken during the exposure of a sol-gel doped block of probe molecules (here bromophenol blue) to an atmosphere containing acetic acid at the saturation vapor pressure. The spectral variations corresponding firstly to a disappearance of the reagent (bromophenol blue, decrease in the intensity of the absorption band at 592nm) and secondly to a formation of the reaction product (appearance of a band absorption at 431 nm).</li><li>the <figref idrefs="f0006">8b</figref> represents the optical density changes corresponding firstly to the disappearance of the reagent, bromophenol blue (solid line curve) and the appearance of the reaction product (bromothymol blue protonated) on the other during the exposing a block doped with bromophenol blue to an atmosphere containing acetic acid at the saturation vapor pressure. The slope at the origin of these two curves is characteristic of the acetic acid concentration in the exposure flow. This reaction is reversible by washing the monolith and desorption of acetic acid.</li></ul>

<u>Example 1: Preparation of a sol-gel block APTES-TMOS</u>

Stage 1:

p0100in an oven heated to 50 ° C for 24 hours multiwell plates of 96-well polystyrene (Greiner Bio-one, Elisa-flat bottom microplates, ref. 655 001) degassing the oven at three times during this period. This step helps degas the polystyrene molds to minimize the release of styrene monomer which may subsequently come trapped in the sol-gel material during the freeze-drying step.

p0101On the magnetic stirrer mixing 3.4 ml of tetramethoxysilane (TMOS, Aldrich, ref 87680.) And 4.8 mL of methanol (Aldrich, ref 65540.) For 2 minutes in a Pyrex beaker placed in a bath - 25 ° C. Then adding 0.2 mL of 3-aminopropyl) triethoxysilane (APTES, Aldrich, ref. 09324) to the mixture with a micropipette. After 2 minutes of additional stirring, 1.7 mL of Millipore ultrapure water is added. Stirring is 30 seconds. A sol used as such in the next step.

Stage 2:

p0102By now the floor to -25 ± 5 ° C and proceeding as quickly as possible, using a micropipette, 38 .mu.l of soil is placed in each well of a multiwell plate reference Greiner Bio-one Elisabethville flat bottom microplates (655,101).

Stage 3:

p0103Once the sol is gelled, it covers the multiwell plate of a gas-permeable film (gas permeable adhesive seals, Abgene, ref. AB-0718). the plate is placed in an oven at 40 ° C for a period of 2 hours. Then outputs the plates of the oven and demolded dies that are placed in airtight containers of polypropylene. It delivers the cans in an oven at 40 ° C for 4 hours to complete the drying.

p0104After drying, sol-gel blocks having the form of monolithic disks. The average diameter of the sol-gel blocks obtained is 3.6 mm and thickness of about 200 ± 25 microns. Their average surface area = 750 m2.g^-1. This was evaluated by establishing the adsorption isotherms and desorption of nitrogen at the temperature of liquid nitrogen and analyzing the isotherms using various analytical models proposed in the literature such as the BET model (Brunauer, Emmet and Taylor).

p0105The average pore volume is 0.67 cm³.g^-1. This was evaluated by establishing adsorption isotherms and desorption of nitrogen at the temperature of liquid nitrogen and by analyzing the isotherms using analytical model DFT (Functional Theory of Gravity).

p0106The pore size distribution was evaluated by the DFT method (Functional Theory of Gravity) based on calculation methods of the interaction potential between molecules of adsorbate and between them and the surface of the pores, allowing to reconstruct a macroscopic data such as the adsorption isotherm from microscopic data such as interaction potentials. The pore shapes model ( "spherical and cylindrical mix") was used for the calculation.

p0107The micropores are defined as pores having pore diameters ≤ 20 Å.

p0108Mesopores are defined as pores having diameters 20 ≤ d ≤ 500 Å.

p0109The results obtained for the Example 1 material, are:<ul><li>Distribution micropore / mesopore (surface) = 35/65%</li><li>Distribution micropores / mesopores (volume) = 15/85%</li></ul>

<u>Example 2 Preparation of a sol-gel block APTES-TMOS</u>

p0110Different shapes and sizes of matrices were carried out:<ul><li>cuboid (Star-pack, ref 47304 and ref ref 271512 and 303 -.... Evergreen, ref 201-3111-010)</li><li>cylindrical (Spex Industries Inc., ref 3111 -. Greiner Bio-One Elisa flat-bottom microplates, ref 655001).</li><li>V (Agar scientific, ref. G3533)</li></ul>

p0111sol-gel blocks were prepared APTES-TMOS as in Example 1 using the cylindrical molds Greiner Bio-one Elisa-flat bottom microplates (ref. 655 101) and were obtained 3.6 mm diameter blocks and of varying thickness between 80 and 1000 microns (depending on the starting volume of soil).

p0112For each of the other molds referenced above and in the case of a material such as that of Example 1, the final sol-gel block (that is to say after drying) maintains the shape of the mold but its volume is about 8 times smaller than the original volume. There is a shrinkage factor equal to 2 in the 3 dimensions because of the expulsion of the residual solvent during the drying step.

<u>Example 3: Preparation of a sol-gel block APTES-TMOS incorporating a probe molecule</u>

p0113Were prepared sol-gel blocks APTES-TMOS incorporating different probe molecules: 4-amino-3-penten-2-one (. TCI ref A5350); bromophenol blue (Sigma-Aldrich, ref 114391.); methyl red (Sigma-Aldrich, ref 250198.); methyl orange (Sigma-Aldrich, ref 114510.); Congo red (Aldrich, ref 860956.); bromocresol green (Sigma-Aldrich, ref. 114359) and bromocresol purple (Sigma-Aldrich, ref. 114375).

p0114The incorporation of 4-amino-3-penten-2-one was made according to three different methods described below:<ul><li>Doping "one-pot" procedure is as in Example 1 but methanol is replaced by methanol + 4-amino-3-penten-2-one. Different concentrations were used (100, 300, 500 and 750 mg of 4-amino-3-penten-2-one in 4.8 mL of methanol). For the rest of the Protocol is exactly the same as in Example 1 except that the drying of the sol-gel blocks is done at 25 ° C.</li><li>"Post-doping liquid" sol-gel blocks such as those obtained in Example 2 were immersed in an aqueous solution concentration of 4-amino-3-penten-2-one equal to 2.10^-3 mol.L^-1 for 2 hours and then dried under inert gas.</li><li>"Post-Doping gas" sol-gel blocks such as those obtained in Example 2 are placed in an enclosure under a reduced pressure of 133.3 Pa (1 torr) in the presence of 4-amino-3-penten powder -2-one. The chamber is heated to 40 ° C for 15 hours, during which 4-amino-3-penten-2-one sublimes and into the sol-gel blocks, more precisely in the pores of the sol-gel blocks . At the end of the exhibition, dry nitrogen is introduced into the chamber to restore atmospheric pressure and recover the sol-gel block doped.</li></ul>

p0115The incorporation of other probe molecules mentioned above (bromophenol blue, methyl red, methyl orange, Congo red, bromocresol green and bromocresol purple) was performed only by the doping method "one-pot".

p0116The procedure is as in Example 1 but replacing methanol with a mixture of methanol and one of the above compounds (bromophenol blue, methyl red, methyl orange; Congo red, bromocresol green and bromocresol purple). Various concentrations were used, prepared from 0.5; 1; 10; thirty ; 50 and 100 mg dissolved in 4.8 mL of methanol. For the rest of protocol, exactly the same as in Example 1 except that the drying of the sol-gel blocks is done in a thermostatically controlled chamber at 25 ° C.

<u>Example 4: Preparation of a system millifluidic</u>

p0117There is provided a millifluidic system consisting of two flat copper plates joined. The macro-fluidic circuit 1 to 3.5 mm wide, 36 mm long and 0.5 mm deep was dug in each copper plate 2 and during assembly the two recessed portions are joined. Millifluidic the circuit 1 is L-shaped and has a throat 3 in the longer leg such that the width of the circuit there is only 1 mm (<figref idrefs="f0001">Fig.2</figref>). Was installs a sol-gel block of Example 2 and in another system a sol-gel block of Example 3 just before the throat 3 at 4. The circuit of throttling enables good posture the sol-gel disk. A hole 5 of the plates is provided at the central location of the sol-gel block for the passage of the analysis light beam. Other openings 6 have been provided to clamp the plates 2.

p0118Was also conducted millifluidiques systems with two plates 2 of PTFE, with two plates 2 of copper and with two plates 2 of stainless steel.

<u>Example 5 Preparation of a measuring device</u>

p0119The assembly of Example 4 Copper was inserted into a measuring chamber made of PTFE equipped with two optical windows made of quartz (<figref idrefs="f0002">Fig.3</figref>).

p0120The exhibition room includes millifluidic system. The latter is held stationary in the exposure chamber through a base 7 provided for this purpose and a cover 8. In addition to maintaining the millifluidic system, the cap is pierced at its center for the passage 9 of the gas mixture.

p0121For optical analysis of the sensor, the optical path of the scanning beam is perpendicular to millifluidic system and passes through the center of the sensor formed by a sol-gel block of Example 2 respectively of Example 3. Standard connectors for fibers (SMA type) and lenses (focal length = 10 mm) placed at the input and the optical output of the exposure chamber enable collimation of the light beam carried by the optical fibers at the inlet and outlet of the exposure chamber. At the end of the exposure chamber, the transmitted light beam is led to a spectrometer (Ocean Optics, QE6500). A sensor of the absorption spectrum was collected before exposure to the test product stream. Upon initial flow millifluidic system and for a duration of between 30 seconds and 2 minutes in the case of a block of Example 2 and between 1 and 120 minutes in the case of a block as those of example 3, an absorption spectrum is collected every second and the data is stored for further processing.

<u>Example 6: Piéaeaae and detrapping of a target compound</u>

p0122An example of measurement of the exposure of a sensor to a nitrogen stream containing 11.86 ppmv of p-xylene is shown in <figref idrefs="f0003">5</figref>.

p0123Was introduced a sol-gel block APTES-TMOS obtained in Example 2 in the millifluidic system of Example 4 and the system of Example 4 was inserted into measuring device of Example 5.

p0124Was prepared a gas mixture containing 11.86 ppmv of para-xylene diluted in nitrogen.

p0125This gas mixture was sent to the flow rate of100 mL.min^-1 in the above system for one minute. Then was passed a flow of ambient air in the circuit millifluidic a flow rate of 4 L · min^-1 for 5 minutes.

p0126Upon introduction of the nitrogen stream containing p-xylene in the system millifluidic spectra were collected every second. The<figref idrefs="f0002">4a</figref> shows the rise of the signal which corresponds to the absorbance of trapped p-xylene, measured over a wavelength range from 235 to 285 nm. It is seen in<figref idrefs="f0003">4b</figref> the decrease in absorbance of p-xylene to a value corresponding to that measured before exposure to p-xylene.

p0127It has also achieved the same type of experiences for different gas concentrations (ranging from 0 to 120 ppmv) and for different types of gas (toluene, benzene, p-xylene, mesitylene) and in different relative humidity conditions ( 0-94%).

<u>Application Example 1: Measurement of a target compound without moisture</u>

p0128The procedure to p-xylene assay absorbance measurement as follows:

p0129Prior to the determination of p-xylene, we created a database of absorption spectra of p-xylene in Example 2 sensor.

p0130Was prepared a gas stream containing 11.86 ppmv of para-xylene diluted in nitrogen. The exposure rate was set at 100 mL · min^-1.

p0131Recording a measurement was conducted in accordance with the following timetable:<ul><li>Establishment of the sol-gel of Example 2 block in all of Example 4 itself placed in the Example 5 device;</li><li>Bleeding the device and stabilization of the lamp and the spectrophotometer (Ocean Optics, QE65000) for 10 minutes;</li><li>Recording the absorption spectrum of the sol-gel block;</li><li>Tilting of the gas inlet valve to allow the exposure of the sol-gel block the gas flow by recording a spectrum per second for one minute;</li><li>Tilting of the valve to perform purging for 5 minutes with air.</li></ul>

p0132Each measurement cycle lasted 6 minutes on average.

p0133The moisture content was 0%.

p0134The results are reported in <figref idrefs="f0003">5</figref>.

p0135It is observed that the sensor response is reproducible. Measuring the signal rise versus time (slope of the curve) gives repeatable values ​​from one cycle to the other with a gap very weak type.

<u>Application Example 2: Measurement of a target compound in the presence of moisture</u>

p0136The procedure for the application example 1, but the relative humidity of the exposure flux was 80%.

p0137The results are reported in <figref idrefs="f0004">6</figref>.

p0138It is observed that the sensor response is reproducible even with the high humidity of the mixture. Measuring the rise of the signal in function of time (slope of the curve) gives repeatable values ​​from one cycle to the other with a low standard deviation of 6.3%.

p0139The sensor has a reproducible response in the field explored relative humidity from 0 to 94%.

<u>Application Example 3: Measurement of a mixture of target compounds without humidity</u>

p0140The procedure for the application example 1, but using a mixture containing 19.9 ppmv of benzene, 7.4 ppmv of mesitylene and 18.3 ppmv of p-xylene.

p0141The results are reported in <figref idrefs="f0004 f0005">7</figref>.

p0142The absorbance signal is deconvoluted from a database of the absorption spectra of the various target compounds in this device.

p0143It is observed that the target compounds of contents extracted from the spectral deconvolution of the spectrum of the mixture of the target compounds are very similar to those in the mixture. Indeed by deconvolution is obtained a content of 19.6 ppmv of benzene, 7.3 ppmv of mesitylene and 17.2 ppmv of p-xylene.

p0144It is concluded that the sensor captures all well monocyclic hydrocarbons, independent or mixed, with the same efficiency as when each of the target compounds is trapped separately.

<u>Application Example 4: Detection of a target compound with a doped matrix to 4-amino-3-penten-2-one by measuring</u><u>fluorescence.</u>

(Not of the invention)

p0145formaldehyde assay was performed by measuring fluorescence as follows:

p0146Prior to the determination of formaldehyde, we have created a database of fluorescence spectra in a sensor of Example 3 doped with 4-amino-3-penten-2-one (Fluoral-P) by the method " one-pot "(500 mg in 4.8 mL of methanol).

p0147a gas stream containing 10 ppbv of formaldehyde diluted in dry air was prepared (FID quality, Messer, ref. 27880). The exposure rate was set at 200 mL · min^-1.

p0148The recording of measurements took place in accordance with the following timetable:<ul><li>introduction of the sol-gel block of Example 3 in the millifluidic system of Example 4 and inserting this assembly into the measuring device of Example 5;</li><li>purging the system and stabilize the excitation lamp and the spectrophotometer (Ocean Optics, QE65000 ref.) for 15 minutes;</li><li>recording the fluorescence spectrum of the sol-gel block;</li><li>tilting of the inlet valve to permit exposure of the sol-gel block to the gas stream and recording a fluorescence spectrum every 30 seconds (pre-excitation for 2 seconds) for 45 minutes.</li></ul>

p0149The results are reported on <figref idrefs="f0004">7a</figref> and <figref idrefs="f0005">7b</figref>.

<u>Application Example 5: Detection of a target compound with a doped matrix bromophenol blue by absorbance measurement.</u>

(Not of the invention)

p0150The experiment consisted of exposing a sol-gel block of Example 3 doped with bromophenol blue by the method "one-pot" (0.25 mg in 4.8 mL of methanol) in an atmosphere saturated with acetic acid (saturated vapor pressure under standard temperature and pressure conditions). Bromophenol blue reacts with acetic acid which has diffused inside the matrix to form a product whose absorption spectrum differs from that of the starting reagent (see<figref idrefs="f0005">8a</figref>). Was measured in this case, the rise of the signal corresponding to the absorption of the product formed during the reaction (absorption band at 431 nm) depending on the duration of exposure, and the decrease of the signal corresponding to the absorption reagent (band at 592 nm) depending on the duration of exposure. These two values ​​are directly proportional to an acetic acid concentration. The results are shown in<figref idrefs="f0005">8a</figref> and <figref idrefs="f0006">8b</figref>.