Patent Application
20250155365
The present invention relates to a novel process for detecting and optionally quantifying amine-type compounds, in particular hydrazine (N2H4), in air.
Hydrazine is classified as a CMR substance (IARC 2B-UE 1B). In 2011, it was incorporated into the REACH regulation candidate list of substances of very high concern. In 2017, the European Union lowered its TLV (8-hour Occupational Exposure Limit value) by a factor of 10, imposing a new threshold of 10 ppb (0.013 mg/m3), applicable from Jan. 17, 2020 at the latest. In addition to human health concerns, hydrazine is also classified as very toxic to aquatic organisms (EU classification H400 and H410).
Due to its CMR nature, hydrazine is no longer an oxidizer for rockets, but is still used in many fields, notably as an organic synthesis intermediate in the pharmaceutical and chemical industries, or as a blowing agent for polymer foams, or as a reducer of metal salts, or even as a corrosion inhibitor in industrial boiler circuit water, for example.
Due to its toxicity, assessing the risks associated with environmental hydrazine releases is important, and requires the ability to detect and optionally quantify the presence of hydrazine in the environment.
To date, this risk assessment is severely limited by the metrology associated with this substance, in particular as regards direct in-situ measurement. Specifically, although relatively sensitive and specific analytical methods do exist (final reading by HPLC-UV), they cannot be readily performed, nor are they compatible with industrial practices. “Instantaneous response” analytical methods are neither sufficiently selective nor sufficiently precise and sensitive to allow expected hydrazine gas concentrations in final discharges to be evaluated.
Hydrazine detection and quantification is currently performed using an indirect method. This method involves collecting the ambient air to be analyzed and trapping the hydrazine in an acidified cartridge, then desorbing it and reacting it with a reagent solution. The adducts formed are then separated by liquid chromatography and analyzed optically.
In addition to the duration of this method, which involves several steps that are difficult to perform directly at the sampling site, potential interference with other gaseous nitrogen compounds is not known, notably in the potential presence of interferents used to basify water or resulting from the degradation of hydrazine, such as ethanolamine (NH2EtOH), morpholine or ammonia (NH3).It is important to be able to measure hydrazine selectively in a direct manner in a concentration range from 1 to 100 ppb in dry to very humid air and in the presence of interferents whose concentration may be 50 to 100 times higher than that of hydrazine.
The process which is a subject of the present invention provides a solution to these problems.
Specifically, the process according to the invention allows hydrazine to be detected and optionally quantified selectively in the presence of water vapor, volatile organic compounds and other nitrogen compounds such as ethanolamine (NH2EtOH), morpholine or ammonia. On contact with hydrazine, the sensor used changes color and the color intensity is proportional to the hydrazine content, allowing this compound to be detected and potentially quantified.
The detection of hydrazine has been the subject of numerous studies, and detection methods are as numerous as they are varied, due to the high chemical reactivity of this compound. As a result, only those methods proposed in the literature are described here, which are capable of covering the required concentration range from 1.3 to 130 μg·m−3 (i.e. 1 to 100 ppb).
Methods for measuring hydrazine in air are less numerous than those for the liquid phase, notably in the target range of 1.3 to 130 μg·m−3 (i.e. 1 to 100 ppb). The current measurement method is described in INRS Data Sheet 21. It is based on the use of benzaldehyde [1]. Hydrazine is collected by air suction through a tube filled with an inert adsorbent (Chromosorb P NAW or equivalent) of 3060 Mesh particle size, impregnated with sulfuric acid. The cartridge contents are desorbed with deionized water and benzaldehyde derivatization is performed. The adduct, benzalazine, is measured by liquid chromatography (HPLC) coupled with UV optical detection [2, 3]. This method allows 30 ppb of hydrazine to be detected within 15 minutes of sampling.
A variant of this method is the use of cassettes containing two glass fiber filters impregnated with sulfuric acid. The hydrazine extraction is performed with an EDTA buffer solution and the derivatization is performed with benzaldehyde. The benzalazine formed is measured by liquid chromatography coupled with UV optical detection [4]. This assay method proves to be sensitive, since it is possible to detect 0.017 ppb of N2H4.
These two methods do not allow direct measurement at the sampling site, and the interference of ammonia or other amines at high concentrations 50 to 100 times that of hydrazine is not known.
Direct measurement methods are also available. In the context of monitoring worker exposure to hydrazine, monomethylhydrazine (MMH) and 1,1-dimethylhydrazine (UDMH) used as rocket fuels at air bases and space centers in the USA, several colorimetric dosimeters have been developed and sold by laboratories [5,6]. The principle is based on the incorporation of an aromatic aldehyde such as vanillin, para-dimethylaminobenzaldehyde (pDMAB) or 2,4-dinitrobenzaldehyde on filter paper or an inert surface. Hydrazine and MMH react with vanillin or 2,4-dinitrobenzaldehyde to form a yellow-colored compound, while the product formed with pDMAB is orange. UDMH reacts with 2,4-dinitrobenzaldehyde to form a yellow-colored compound, and thus there is no reaction with vanillin and pDMAB. Colorimetric dosimeters based on vanillin and para-dimethylaminobenzaldehyde are sold by the company DODTEC [7] and CHEMSEE [8]. They do not allow exact quantification, but only the estimation of hydrazine and monomethylhydrazine contents in air from 25 ppb up to 1.2 ppm.
In patent U.S. Ser. No. 00/571,9061 A [9], Rose-Pehrsson et al. propose a process allowing the selective detection and quantification of liquid or gaseous hydrazine, monomethylhydrazine and 1,1-dimethylhydrazine by derivatization with aromatic carboxyaldehydes and fluorimetric analysis. Selectivity is based on the reactivity of three derivatizing agents, ortho-phthalaldehyde (OPA), napthalene-2,3-dicarboxaldehyde (NDA) and anthracene-2,3-dicarboxaldehyde (ADA) with hydrazine, monomethylhydrazine and 1,1-dimethylhydrazine as a function of the pH of the reagent solution. These authors thus developed a complex device which allows ambient air to be pumped into and sparge a reagent solution whose composition (OPA or NDA or ADA) and pH must be modified to produce selectivity. Although the detection limit reached is ppb, analysis of the gas mixture to be analyzed requires numerous reagent and pH change steps, followed by fluorimetric analysis. Moreover, there was no study of interference, notably with other amines at concentrations 50 to 100 times higher, which are liable to modify the pH of the solution.
For precise measurements, a number of commercial devices are available. The portable electrochemical detector from the company Interscan, model 4180-100b [10] allows detection of hydrazine in the range 10 to 100 ppb in less than 1 second, with a high detection limit of 10 ppb. The method is also non-selective, as the sensor also detects NH3, NOx, CO and other organic amines.
High sensitivity may be obtained using devices equipped with a photoionization detector (PID), such as ppbRAE 3000 from the company RAE [11]. The photoionization detector, equipped with a 10.6 eV lamp, allows hydrazine ionization and measurement of a few ppb in 3 seconds. Detection is not selective, however, as a large number of volatile organic compounds present in the air with ionization potentials below 10.6 eV are also detected, such as NH3, ethanolamine and morpholine.
Hydrazine ionization followed by ion mobility measurement using an Ion Mobility Spectrometer (IMS) allows contents of about ten ppb (20-30 ppb) to be reached, while at the same time being selective in terms of the choice of carrier gas. When using a radioactive source, the IMS (such as the SABRE 4000 portable detector [12] or Environics' ChemPro 100i [13]) must be under the responsibility of a person competent in radiation protection. This technique is favored by armies and police forces for the detection of chemical weapons and illicit products. Its application in the public domain has developed more recently with the development of new non-radioactive ionization sources (corona effect) such as the PAIMS portable detector from the company MaSaTECH [14] or LCD 3.3 from Smiths Detection [15].
The prior art in hydrazine measurement shows that the only simple method currently adopted, using benzaldehyde as the reagent, can be used with good selectivity and sensitivity. However, hydrazine measurement in the air compartment requires adsorption and then desorption and derivatization steps, followed by optical analysis, which are difficult to perform on site. Furthermore, for this method, interference with high concentrations of NH3, ethanolamine or morpholine gas in the atmosphere is not known.
There is thus a real need for a hydrazine-selective process for the direct detection and, optionally, direct quantification of hydrazine in air, which is compatible with the presence of high concentrations of interferents and readily performable on site.
The process according to the invention addresses these issues.
A first subject of the invention is a nanoporous sensor composed of a nanoporous silicate sol-gel matrix enclosing a reagents composition, said reagents composition comprising a mixture of 4-(dimethylamino) cinnamaldehyde and polystyrenesulfonic acid.
Another subject of the invention is a process for preparing a nanoporous sensor according to the invention, said process comprising the following steps:
A subject of the present invention is also a process for detecting at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine, using a nanoporous sensor according to the invention, said process comprising the steps of:
Another subject of the invention is the use of a nanoporous sensor according to the invention, for the detection and/or quantification of at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine.
The present invention also relates to a device for detecting at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine, in a gas sample to be analyzed, said device comprising a cell enclosing a nanoporous sensor according to the invention and comprising:
Other features, details and advantages will be seen on reading the detailed description hereinbelow, and on analysis of the appended drawings, on which:
The subject of the present invention is a nanoporous sensor composed of a nanoporous silicate sol-gel matrix enclosing a reagents composition, said reagents composition comprising a mixture of 4-(dimethylamino) cinnamaldehyde and polystyrenesulfonic acid.
For the purposes of the present invention, silicate sol-gel matrix means a material obtained via a sol-gel process which consists in using silicon alkoxides of formula Si(OR)x, where R is an alkyl group, as precursors.
During the sol-gel process, alkoxy groups (OR) are hydrolyzed in the presence of water to form silanol groups (Si—OH). These condense to form siloxane bonds (Si—O—Si—). The result is small particles, generally less than 1 μm in size, which aggregate to form clusters that remain in suspension without precipitating, forming a sol. The increase in clusters and their condensation increase the viscosity of the medium, which then gels. A porous solid material is obtained by drying the gel, with the solvent being expelled from the polymeric network formed (syneresis). Sol-gel matrices obtained from silicon alkoxides of formula Si(OR)x are referred to as silicate sol-gel matrices in the present patent application.
For the purposes of the present invention, the term “nanoporous” means having pores with a size of less than 100 nm.
According to a particular embodiment, the nanoporous matrix according to the invention is an essentially microporous matrix. Thus, according to this embodiment, the sensor may also be described as essentially microporous. An essentially microporous material (essentially microporous sensor or essentially microporous matrix) means a material in which at least 80% of the pores are micropores.
According to the IUPAC definition, micropores are characterized by a width not exceeding 2 nm (IUPAC. Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S. J. Chalk. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook).
On contact with an amine-type compound, notably gaseous hydrazine, the nanoporous sensor according to the invention changes color due to the formation of DMACA-N2H4 and 2DMACA-N2H4 between hydrazine (N2H4) and 4-(dimethylamino) cinnamaldehyde (DMACA) in the presence of polystyrenesulfonic acid, which allows this reaction to be catalyzed. The absorbance variations are correlated with hydrazine content in the air.
The reaction between hydrazine (N2H4) and 4-(dimethylamino) cinnamaldehyde (DMACA) is advantageously catalyzed by an acid derived from a polymer, in particular polystyrenesulfonic acid. The choice of this type of acid, and in particular polystyrenesulfonic acid, has many advantages.
Firstly, this acid is a high molecular weight polymer including an SO3H acid function for each styrene monomer. As a result, the number of available protons is particularly high, allowing the pore acidity to be adjusted to catalyze the reaction between DMACA and N2H4.
Moreover, inorganic acids and organic acids of low molecular weight have the drawback that acid vapors may be released during the step of drying the sol-gel matrix, which may result in evaporation of the acid in this case too. Thus, a volatile inorganic acid such as HCl (or an organic acid such as acetic acid) could evaporate from the sol-gel matrix, resulting in a loss of efficacy, or even preventing the sensor from functioning. This drawback is not present for acids derived from a polymer, such as polystyrenesulfonic acid, as these acids are not volatile.
Finally, another major advantage of polymer-derived acids relates to the deployment of acidic polymer chains in the small pores of the sol-gel matrix. This deployment of acidic functional groups in the pores makes it possible, firstly, to acidify each pore and, secondly, to strongly restrict polymer diffusion into the pore network, preventing it from migrating toward the sensor surface.
Advantageously, the nanoporous sensor according to the invention is characterized by a large specific surface area for adsorption. Specifically, it has a specific surface area for adsorption of from 700 to 2500 m2·g−1, preferably from 800 to 2000 m2·g−1.
The specific surface area for adsorption, pore volume and pore size distribution are determined by analyzing the liquid nitrogen adsorption-desorption isotherm using the Density Functional Theory (DFT) model. The BET (Brunauer-Emmett-Teller) method is an analytical method that enables deduction of the specific surface area for adsorption.
The nanoporous sensor according to the invention preferentially has a pore volume of 0.1 to 0.9 cm3·g−1, preferably of 0.2 to 0.8 cm3·g−1, even more preferentially of 0.2 to 0.6 cm3·g−1. The pore volume represents the volume occupied by the pores per gram of sensor. The pore volume of the material is obtained from the nitrogen adsorption isotherm at liquid nitrogen temperature.
Advantageously, the nanoporous sensor according to the invention has a proportion of micropores greater than 75%, preferably greater than 80%, more preferably ranging from 85% to 95%, the remainder to 100% corresponding to the proportion of mesopores.
According to the IUPAC definition (IUPAC. Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S. J. Chalk. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook), the term “micropores” means pores with a width not exceeding 2 nm, and “mesopores” means pores with a width of between 2 and 50 nm. Pores with a width greater than 50 nm are referred to as macropores according to the same IUPAC reference.
The nanoporous sensor according to the invention preferentially has a mesopore content of less than 25%, preferably less than 20%, and more preferentially ranging from 5% to 15%, the remainder to 100% corresponding to the micropore content.
In particular, the nanoporous sensor according to the invention may have micropores with a diameter ranging from 0.3 to 2 nm, preferably from 0.5 to 2 nm.
The nanoporous sensor according to the invention may also be characterized in that it advantageously has mesopores with a diameter of between 2 and 20 nm, preferably between 2 and 15 nm.
The nanoporous sensor according to the invention preferably has a ratio r of polystyrenesulfonic acid and 4-(dimethylamino) cinnamaldehyde concentrations of 1 to 20, preferably 2 to 15, even more preferentially 10.
This ratio is calculated from the molar concentrations of polystyrenesulfonic acid and 4-(dimethylamino) cinnamaldehyde (r=[H+]/[DMACA]). For this calculation, the molar mass of the polystyrenesulfonic acid monomer (M=184 g/mol) is used so as to convert the polystyrenesulfonic acid (PSS) mass concentration into a molar concentration. For example, a PSS concentration of 9.2 g·L−1 corresponds to a concentration of 0.05 mol·L−1 (=9.2/184). Thus, with a DMACA concentration of 5.10−3 mol·L−1 and a PSS concentration of 9.2 g·L−1 (0.05 mol·L−1), the ratio r is equal to 10.
The ratio of the concentrations of polystyrenesulfonic acid and 4-(dimethylamino) cinnamaldehyde may also be expressed as a ratio r′ of the mass concentrations of the two species (r′=[H+]/[DMACA]), this ratio r′ ranging from 1 to 20, preferably from 2 to 15, even more preferentially 11. For example, with a DMACA concentration of 5.10−3 mol·L−1 corresponding to 0.876 g·L−1 (with M=175.23 g·mol−1) and a PSS concentration of 9.2 g·L−1, the ratio r′ is equal to 10.5.
Another subject of the present invention is the process for preparing the nanoporous sensor according to the invention, said process comprising the following steps:
According to a preferred embodiment of the process according to the invention, the organosilyl precursor is chosen from precursors with rapid hydrolysis and condensation and no long hydrophobic chains, such as tetramethoxysilane Si(OCH3)4), methyltrimethoxysilane CH3Si(OCH3)3, ethyltrimethoxysilane (C2H5)Si(OCH3)3, 3-aminopropyltriethoxysilane (C3H6NH2)Si(OC2H5)3, 3-aminopropyltrimethoxysilane (C3H6NH2)Si(OCH3)3), (3-(methylamino)propyl)trimethoxysilane (C3H6NHCH3)Si(OCH3)3, 3-carboxypropyltriethoxysilane (C3H6CO2H)Si(OC2H5)3, 3-carboxypropyltrimethoxysilane (Si(C3H6CO2H) (OCH3)3), tetraethoxysilane and mixtures thereof. The precursor is preferentially chosen from tetramethoxysilane (TMOS), tetraethoxysilane (TEOS) and mixtures thereof.
Step a) of the process according to the invention is preferentially performed in a solvent which may be water or a water/alcohol mixture, the alcohol preferably being a C1 to C6 aliphatic alcohol, more preferentially methanol or ethanol, or a mixture of water with a solvent chosen from acetone, formamide and methyl ethyl ketone.
In the process according to the invention, the sol synthesis step a) is advantageously performed first by mixing an organosilyl precursor chosen from tetramethoxysilane Si(OCH3)4), methyltrimethoxysilane CH3Si(OCH3)3, ethyltrimethoxysilane (C2H5)Si(OCH3)3, 3-aminopropyltriethoxysilane (C3H6NH2)Si(OC2H5)3, 3-aminopropyltrimethoxysilane (C3H6NH2)Si(OCH3)3), (3-(methylamino)propyl)trimethoxysilane (C3H6NHCH3)Si(OCH3)3, 3-carboxypropyltriethoxysilane (C3H6CO2H)Si(OC2H5)3, 3-carboxypropyltrimethoxysilane (Si(C3H6CO2H) (OCH3)3), tetraethoxysilane and mixtures thereof, with 4 (dimethylamino) cinnamaldehyde in the solvent, said solvent comprising water, followed by addition of polystyrenesulfonic acid.
The addition of polystyrenesulfonic acid is preferably performed dropwise, as dissolution of the acid in the mixture is exothermic. Alternatively, the addition of the polystyrenesulfonic acid solution can be performed by adding to the mixture of organosilyl precursor and 4-(dimethylamino) cinnamaldehyde in solvent, this mixture being maintained at a temperature below 10° C.
According to a preferred embodiment, step a) of the process according to the invention is characterized in that the mole ratio of organosilyl precursor to solvent ranges from 1/20 to ½, preferably from 1/18 to ⅓, even more preferentially from 1/16 to ¼.
Advantageously, step a) of the process according to the invention is performed at room temperature, the term “room temperature” denoting a temperature of about 20-22° C.
According to a preferred embodiment, the mixture obtained at the end of step a) is kept stirring prior to gelling step b). Preferably, this stirring is performed at room temperature for a period ranging from 2 to 48 hours, preferably 24 hours.
The gelling step b) may be performed after the mixture obtained at the end of step a) has been poured into a mold. When a mold has thus been used, the process according to the invention may then include, after drying step c), a step for demolding the nanoporous sensor.
The gelling step b) may advantageously be performed at a relative humidity of 100%, at a temperature of between 2° and 25° C., preferably 22° C. This step b) preferably has a duration of 1 to 15 days, preferably 1 to 5 days, even more preferentially 2 days.
Drying step c) may advantageously be performed in a closed chamber, for example a desiccator, where humidity and temperature are preferably controlled.
Drying step c) is advantageously performed by flushing the closed chamber with a stream of moist, inert gas, preferably argon. The relative humidity of the applied gas stream can advantageously be controlled, being initially 100%, and then reduced in stages to about 25%. The humidity in the closed chamber may thus be reduced during the drying step to reach 25-28% relative humidity.
This step c) preferably lasts from 15 to 60 days, preferably from 20 to 40 days.
After drying, the nanoporous sensor obtained is preferentially stored protected from light, at a temperature ranging from 2 to 10° C., preferably from 4 to 8° C., even more preferentially 6° C.
The nanoporous sensor according to the invention and obtainable via the process of the invention advantageously has a parallelepiped shape. It advantageously has dimensions of the order of a millimeter, for example a height of 7.5 to 10.3 mm, a width of 4.8 to 6.4 mm and a thickness of 1 to 1.3 mm.
Another subject of the present invention is a process for detecting in a gas sample to be analyzed at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine, using a nanoporous sensor according to the invention, said process comprising the steps of:
This process advantageously allows selective measurement of an amine-type compound, in particular hydrazine, in a direct manner, in a concentration range from 1 to 100 ppb in dry to very humid air and in the presence of interferents whose total concentration may be at most 200 times higher than that of the amine to be detected, in particular hydrazine.
For the purposes of the present invention, the term “dry air” means air with a moisture content less than or equal to 25%.
Thus, the process according to the invention allows measurements to be performed on a gas sample with a relative humidity ranging between 25% and 100%, preferably from 30% to 100%.
The process according to the invention thus offers real advantages relative to the prior art processes which do not allow this measurement to be performed directly, whatever the moisture content, over this concentration range and in the presence of interferents.
In addition to detection, the process according to the invention may also allow determination in a gas sample to be analyzed of the concentration of at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine. Thus, according to a particular embodiment, the present invention relates to a process for detecting and quantifying in a gas sample to be analyzed at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine, using a nanoporous sensor according to the invention, said process comprising the steps of:
Step b) of the process according to the invention may notably comprise a step of measuring the absorbance of the nanoporous sensor as a function of time.
The analytical method which allows the detection and determination of the contents of hydrazine and interferents bearing a primary or secondary amine function by absorbance measurements as a function of time involves knowledge of the absorption spectra of the 4-(dimethylamino) cinnamaldehyde (DMACA)/polystyrenesulfonic acid (PSS) mixture in the presence of the amine-type compounds targeted for different concentrations of said amine compounds.
From these absorption spectra, calibration curves representing the temporal evolution of absorbance as a function of concentration for each of said amine-type compounds can be established.
Thus, when the sensor according to the invention is placed in the presence of a gas sample to be analyzed, the absorbance measurement result obtained as a function of time can be correlated with the calibration curves previously established, leading to the determination of the presence or absence of an amine-type compound and optionally to the determination of its concentration.
Detection and, optionally, quantification of hydrazine, ethanolamine, ammonia or morpholine by absorbance measurements is made possible by virtue of the reaction taking place between these compounds and 4-(dimethylamino) cinnamaldehyde (DMACA) in the presence of polystyrenesulfonic acid (PSS), which acts as a catalyst and results in the formation of complexes which have absorption spectra that are detectable in the UV-visible range, for example using a spectrophotometer.
Thus, the reaction between N2H4 and DMACA catalyzed in the presence of polystyrenesulfonic acid gives rise to the formation of the addition complexes IDMACA-N2H4 and 2DMACA-N2H4 according to the equations represented in
The formation of these two complexes 1DMACA-N2H4 and 2DMACA-N2H4 may be visualized by absorbance peaks at 388 and 558 nm respectively ([
In the context of the present invention, the peak at 388 nm is used to detect and quantify hydrazine, as it is the more sensitive of the two peaks formed. Specifically, the 2DMACA-N2H4 complex is formed more slowly and in smaller amounts than the DMACA-N2H4 complex for steric and kinetic reasons.
In the case of ammonia, DMACA (H+) deprotonates in the presence of a strong base such as NH3, to form neutral DMACA, absorbing intensely at 420 nm ([
Another subject of the present invention is the use of a nanoporous sensor according to the invention for the detection, or quantification, or detection and quantification of at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine.
The nanoporous sensor according to the invention can be used in either dynamic or static mode. Thus, the nanoporous sensor may be placed in a gas stream to be analyzed and circulated by a fluidic circuit, or alternatively the sensor may be placed in a chamber comprising the gas sample to be analyzed.
Another subject of the present invention is a device (1) for detecting at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine, in a gas sample to be analyzed, said device comprising a cell (11) containing a nanoporous sensor according to the invention, said cell comprising:
Advantageously, the device according to the invention includes a fluidic circuit suitable for circulating the gas sample to be analyzed through the cell (11), generating a gas stream from the gas inlet (111) to the nanoporous sensor and then to the gas outlet (112).
According to a preferred embodiment, the fluidic circuit according to the invention comprises a flow regulator (2) suitable for regulating the flow rate of the gas stream. The flow rate regulator (2) may be composed of a shut-off valve (21) and a control needle valve (22).
Advantageously, the device according to the invention also comprises a light source (3) and a spectrophotometer (4), in which the optical input (113) of the cell is connected to the light source (3) and the optical output (114) of the cell is connected to the spectrophotometer (4). The light source (3) and the spectrophotometer (4) may thus constitute the optical analysis part of the device.
According to a preferred embodiment, the fluidic circuit of the device according to the invention also comprises a temperature sensor suitable for measuring the temperature of the gas stream.
Advantageously, the device according to the invention also comprises a humidity sensor suitable for measuring the humidity of the gas stream.
Advantageously, the device according to the invention also comprises a flow meter (5) suitable for measuring the gas stream flow rate.
The fluidic circuit may thus take account of:
The device according to the invention may thus operate in the following manner: the air or gas sample to be analyzed can be sucked in using a pump (6), which may be miniature, and initially passed through an inlet manifold (7), where the temperature and humidity of the gas sample are measured. The manifold (7) can then distribute the gas sample to two outlets. The pump may notably have a flow rate ranging from 50 to 1100 ml/min.
The first outlet may move air toward the cell (11) containing the nanoporous sensor. The cell may be placed upstream of a flow meter (5) connected to an output manifold (8), which is itself connected to the pump (6). The flow meter allows the gas stream velocity in the exposure cell to be set.
The second outlet of the inlet manifold (7) may be connected to the outlet manifold (8) via a shut-off valve (21) and a control needle valve (22). This assembly then constitutes a leakage circuit. This configuration allows the exposure flow rate of the sensors to be varied (if different types of sensor are used), as the pump operates continuously at a fixed flow rate, for example 1.1 L/min. The shut-off valve allows the leakage circuit to be shut off, in order to purge the measuring circuit if necessary.
The optical analysis part includes a light source (3) which can probe the sensor and a spectrophotometer (4), the latter possibly being miniature, which collects the light transmitted by the sensor and transforms it into electrical current. The spectrophotometer (4) can operate at wavelengths ranging from UV through visible to IR, the wavelength being chosen according to the measurement to be performed.
The light source (3) may consist of two LEDs linked by optical fibers, or of a miniature lamp. The light source may be a UV or visible or UV-visible source.
For the detection of hydrazine at 388 nm, NH3 at 420 nm, ethanolamine at 474 nm or morpholine at 490 nm, the combination of a UV LED and a visible LED affords the 380-800 nm wavelength range. Other LED choices are also possible, depending on the optical response of the sensor. The light is conveyed to the exposure cell, for example, using an optical fiber. At the output of the exposure cell, the transmitted light is conveyed to the miniature spectrophotometer (4), which has a wide response range, for example from 337.5 to 822 nm. An example of a device according to the invention is represented in [
According to a preferred embodiment, the device according to the invention is characterized in that the cell comprises a nanoporous sensor support and a parallelepipedic, preferably cubic, case comprising four side faces and a front face forming at its center a housing for receiving the nanoporous sensor support, two opposite side faces presenting the gas inlet and outlet, two opposite side faces presenting the optical input and output, the front face having an aperture for inserting the nanoporous sensor support into its housing (
The cell of the device according to the invention may thus include two elements.
The first element is its body, which may consist of a square block (
The second element may be a removable part, made of stainless steel for example (
An example of a cell of the device according to the invention is represented in [
The sensor may be exposed to the gas stream over its entire length and on both sides. The probe light beam, coming from the light source and carried by an optical fiber, arrives perpendicular to the gas stream and is focused on the sensor at the fiber outlet. The probed surface may be a 5.7 mm2 circle (2.7 mm diameter). The optical path of analysis, which may range from 1 to 2 mm, corresponds to the thickness of the inserted nanoporous sensor.
Depending on the sensor's geometry, for example a disk or a parallelepiped, the removable part may be designed to position the sensor correctly and expose it to the gas stream over its largest surface area.
According to a preferred embodiment, the sensor is positioned between two half-cylinders, hollowed out to allow the gas stream to pass above and below the sensor ([
According to a preferred embodiment, the device according to the invention is characterized in that the nanoporous sensor support comprises two diametrically opposed passage orifices, optically connected to the optical input and output.
Advantageously, the device according to the invention also comprises a computer and a battery to provide electrical power to said device and thus make it energy self-sufficient.
The device according to the invention may also comprise a screen allowing the user to interact with the system's elements by computer.
The device according to the invention may also comprise a power supply and control board.
The components of the device, composed of the fluidic circuit and the optical analysis part, may thus be positioned in a compartment of a portable element. This portable element may then include a second compartment containing a computer suitable for controlling the measurements, and a third compartment including a power supply for operating the device as a whole.
Thus, according to a particular embodiment, the device according to the invention may be integrated into a case comprising several levels, notably three levels. The computer may, for example, be located on the upper level of the case, the device according to the invention on the middle level and the power supply on the lower level.
According to a preferred embodiment, the device according to the invention is characterized in that it is portable.
Advantageously, the device according to the invention allows quantification of said amine-type compound(s) in the gas sample to be analyzed.
In a 1 L bottle, 14.2 mg of DMACA, 40.969 mL of H2O and 84.598 mL of TMOS are mixed. The solution is kept stirring at room temperature and 0.449 mL of 30% PSS is added dropwise, as the dissolution of PSS in the mixture is exothermic. The mole ratio of silylated precursor to water in the mixture is TMOS/H2O=1/4. The respective final concentrations of DMACA and PSS are 6.25×10−4 M and 1.18 g·L−1, i.e. [H+]˜6.25×10−3 M.
The sol is kept stirring for 24 h at room temperature and then poured into a polypropylene mold containing 350 wells of 0.3 cm3 volume. The mold is placed in a 10 L desiccator maintained at 100% relative humidity until the sol gels. This step takes 2 days at 22° C. for Hy1. Drying of the gels is then performed by flushing the desiccator with a stream of moist Ar at 300 mL·min−1. The relative humidity of the Ar stream, initially 100%, is reduced in stages to 80%, 50% and then 0%. Drying takes about 1 month at 22° C., during which the humidity in the desiccator reduces to 25-28% relative humidity. The mold is then removed from the desiccator. After removing from the mold, parallelepiped sensors with dimensions of 9.6(H)*6.0(L)*1.26 (thickness) mm are obtained for an initial solution of 0.3 mL. The final volume of the sensors obtained has shrunk by a factor of 4.2. The sensors are stored in a cool place at 6° C., protected from light.
Same procedure as Hy1 with 14.2 mg of DMACA, 84.598 mL of TMOS, 40.969 mL of deionized H2O and 0.673 mL of 30% PSS. The mole ratio of silylated precursor to water in the mixture is TMOS/H2O=1/4. The respective final concentrations of DMACA and PSS are 6.25×10−4 M and 1.77 g·L−1, i.e. [H+]˜9.38×10−3 M. The gelling time of the sensors in the desiccator maintained at RH=100% is 2 days at 22° C. Drying in stages from RH=80%, 50% to 0% takes about 40 days at 22° C., during which the humidity in the desiccator reduces to 25-28% relative humidity. After removing from the mold, sensors with dimensions of 9.7(H)*6.1(L)*1.26 (thickness) mm and a shrinkage factor of 4 are obtained. The sensors are stored in a cool place at 6° C., protected from light.
Same procedure as Hy1 with 28.5 mg of DMACA, 84.598 mL of TMOS, 40.969 mL of deionized H2O and 0.898 mL of 30% PSS. The mole ratio of silylated precursor to water in the mixture is TMOS/H2O=1/4. The respective final concentrations of DMACA and PSS are 1.25×10−3 M and 2.34 g·L−1, i.e. [H+]˜1.25×10−2 M. The gelling time of the sensors in the desiccator maintained at RH=100% is 2 days at 22° C. Drying in stages from RH=80%, 50% to 0% takes about 1 month at 22° C., during which the humidity in the desiccator reduces to 25-28% relative humidity. After removing from the mold, sensors with dimensions of 9.5(H)*6.1(L)*1.24 (thickness) mm and a shrinkage factor of 4.2 are obtained. The sensors are stored in a cool place at 6° C., protected from light.
Same procedure as Hy1 with 113 mg of DMACA, 81.496 mL of H2O and 43.91 mL of TMOS and 3.563 mL of 30% PSS. The mole ratio of silylated precursor to water in the mixture is TMOS/H2O=1/16. The respective final concentrations of DMACA and PSS are 5×10−3 M and 9.2 g·L−1, i.e. [H+]˜5×10−2 M. Gelation of the sensors in the desiccator maintained at RH=100% takes place after 5 days at 22° C. Drying in stages from RH=80%, 50% to 0% takes about 1.5 months at 22° C., during which the humidity in the desiccator reduces to 25-28% relative humidity. After removing from the mold, sensors with dimensions of 8.37(H)*4.94(L)*1.03 (thickness) mm and a shrinkage factor of 7 are obtained. The sensors are stored in a cool place at 6° C., protected from light.
Same procedure as Hy1 with 87.9 mg of DMACA, 33.777 mL of TMOS, 13.587 mL of H2O and 2.77 mL of 30% PSS. The mole ratio of silylated precursor to water in the mixture is TMOS/H2O=1/4. The respective final concentrations of DMACA and PSS are 1×10−2 M and 18.4 g·L−1, i.e. [H+]˜1×10−1 M. The gelling time of the sensors in the desiccator maintained at RH=100% is 5 days at 22° C. Drying in stages from RH=80%, 50% to 0% takes about 1 month at 22° C., during which the humidity in the desiccator reduces to 25-28% relative humidity. After removing from the mold, sensors with dimensions of 10.2(H)*6.4(L)*1.3 (thickness) mm and a shrinkage factor of 3.5 are obtained. The sensors are stored in a cool place at 6° C., protected from light.
Same procedure as Hy1, with 226 mg of DMACA, 43.91 mL of TMOS, 77.933 mL of water and 7.126 mL of PSS. The mole ratio of silylated precursor to water in the mixture is TMOS/H2O=1/16. The final concentrations of DMACA and PSS are 1×10−2 M and 18.4 g·L−1, i.e. [H+]˜1×10−1 M. The gelling time of the sensors in the desiccator maintained at RH=100% is 3 days at 22° C. Drying in stages from RH=80%, 50% to 0% takes about 49 days at 22° C., during which the humidity in the desiccator reduces to 25-28% relative humidity. After removing from the mold, sensors with dimensions of 8.4(H)*5.0(L)*1.05 (thickness) mm sensors and a shrinkage factor of 6.7 are obtained.
56.5 mg of DMACA, 21.258 mL of H2O and 10.974 mL of TMOS are mixed in a 1 L bottle. The solution is kept stirring at room temperature while slowly adding 613 mg of para-toluenesulfonic acid, C7H7—SO3H. When the acid is added to this mixture, the mixture releases heat. The mole ratio of silylated precursor to water is TMOS/H2O=1/16. The respective final concentrations of DMACA and para-toluenesulfonic acid are 1×10−2 M and 1×10−1 M.
The sol is kept stirring for 3 h at room temperature and then poured into a polypropylene mold. The mold is placed in a 10 L desiccator maintained at 100% relative humidity until the sol gels. This step takes 5 days at 22° C. Drying is performed by flushing the desiccator with an Ar stream of 300 mL·min−1, while gradually reducing the relative humidity in the desiccator from 100% to 80%, 50% and then 0% RH. Drying takes about 1 month at 22° C., during which the humidity in the desiccator reduces to 25-28% RH. The mold is removed from the desiccator. After removing from the mold, parallelepiped-shaped sensors with dimensions of 7.57(H)*4.8(L)*1.0 (thickness) mm and a shrinkage factor of 8.2 are obtained. The sensors are stored in a cool place at 6° C., protected from light.
Same procedure as Hy1 with 1.139 g of DMACA, 84.598 mL of TMOS, 5.054 and 35.916 mL of 30% PSS. The respective final concentrations of DMACA and PSS are 5×10−2 M and 95.2 g·L−1, i.e. [H+]˜5×10−1 M. The gelling time of the sensors in the desiccator maintained at RH=100% is 4 days at 22° C. Drying in stages from RH=80%, 50% to 0% takes about 1 month at 22° C., during which the humidity in the desiccator reduces to 25-28% relative humidity. After removing from the mold, sensors with dimensions of 11.2(H)*6.4(L)*1.2 (thickness) mm and a shrinkage factor of 3.4 are obtained.
Same procedure as Hy1 with 596.5 mg of DMACA, 84.598 mL of TMOS, 23.012 mL of water and 17.958 mL of 30% PSS. The mole ratio of silylated precursor to water is TMOS/H2O=1/4. The respective final concentrations of DMACA and PSS are 2.5×10−2 M and 47.6 g·L−1, i.e. [H+]˜2.5×10−1 M. The gelling time of the sensors in the desiccator maintained at RH=100% is 2 days at 22° C. Drying in stages from RH=80%, 50% to 0% takes about 1 month at 22° C., during which the humidity in the desiccator reduces to 25-28% relative humidity. After removing from the mold, sensors with dimensions of 10.24(H)*6.5(L)*1.25 (thickness) mm and a shrinkage factor of 3.6 are obtained.
The porosity properties of the nanoporous sensors, such as specific surface area for adsorption, pore volume or the size distributions of the micropores and mesopores, were determined by establishing adsorption-desorption isotherms for N2 at the temperature of liquid N2. The table below collates these data.
The percentages of micropores and mesopores given here correspond to the distribution of adsorption surface area as a function of pore diameter. This percentage would be different considering the pore volume distribution as a function of pore diameter.
The Hy1 sensor was exposed to a humid gas mixture (relative humidity RH=50%) containing 5 ppm of NH3. NH3 does not react with DMACA (H+) but induces deprotonation of DMACA (H+) to form neutral DMACA. In the porous material, neutral DMACA exhibits a broad absorption band in the UV-near visible range, with the maximum centered at 420 nm (
Hy3 sensors are exposed to different concentrations of N2H4 over a wide concentration range from 1 to 114 ppb. The relative humidity of the gas mixtures was kept fixed at 50%. For each exposure to a given N2H4 content, the rate of formation of the IDMACA-N2H4 complex at 388 nm was deduced. By plotting the rate of formation of the IDMACA-N2H4 complex as a function of N2H4 concentration, a calibration curve for the detection of N2H4 at 388 nm is obtained. An example of an N2H4 calibration curve established for the Hy3 sensor is shown in
The effect of the relative humidity of gas mixtures on the N2H4 calibration curve of the Hy3 sensor is investigated ([
The response of the Hy3 sensor to N2H4 in the presence of NH2EtOH is studied ([
The response of the Hy3 sensor to N2H4 in the presence of morpholine is studied ([
The response of the Hy3 sensor to N2H4 in the presence of NH3 is studied ([
The response of the Hy3 sensor to N2H4 in the presence of the two potential interferents, NH3 and NH2EtOH, is studied ([
The response of the Hy3 sensor to N2H4 in the presence of the interferents, NH3 and morpholine, is studied ([
The responses of the Hy1, Hy2 and Hy3 sensors to N2H4 are studied ([
The responses of the Hy8 and Hy9 sensors to N2H4 are studied ([
The responses of Hy4, Hy5, Hy6 and Hy7 sensors to N2H4 are studied ([
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2312243 | Nov 2023 | FR | national |
