Method for detecting amine-type compounds in water and air compartments

Abstract

The present invention relates to a method for detecting at least one amine-type compound, said compound being selected from hydrazine, ethanolamine and morpholine, using a reagent composition comprising a mixture of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid, on said composition and its use.

Description

Title of the invention: Method for detecting amine-type compounds in water and air compartments. Technical field

[0001] The present invention relates to a new method for detecting and optionally quantifying amine-type compounds, in particular hydrazine (N2H4), suitable for both water (hydrazine in aqueous solution) and air (hydrazine in the atmosphere) compartments.

[0002] Hydrazine is a substance classified as CMR (IARC 2B-EU IB). In 2011, it was added to the Candidate List of Very High Concern (CHC) under the REACH Regulation. In 2017, the European Union lowered its 8-hour occupational exposure limit (OEL) by a factor of 10, imposing a new threshold of 10 ppb (0.013 mg / m³), applicable no later than January 17, 2020. In addition to its health implications, hydrazine is classified as very toxic to aquatic organisms (EU classification H400 and H410).

[0003] Due to its CMR character, hydrazine is no longer an oxidizer for rockets, but remains used in many fields, notably as an intermediate in organic synthesis in the pharmaceutical and chemical industries, or as a blowing agent for polymer foams, or as a reducer of metal salts or as a corrosion inhibitor in the water of industrial boiler circuits, for example.

[0004] Because of its toxicity, the assessment of 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.

[0005] The assessment of these risks is currently severely limited by the metrology associated with this substance, particularly with regard to direct in-situ measurement. Indeed, despite the existence of relatively sensitive and specific analytical methods (final reading by HPLC-UV), these cannot be easily implemented or be compatible with industrial practices. "Instantaneous response" analytical methods are neither sufficiently selective nor sufficiently precise and sensitive to allow for the assessment of expected gaseous hydrazine concentrations in final discharges.

[0006] The process which is the subject of the present invention provides a solution to these problems.

[0007] Indeed, the process according to the invention makes it possible to detect and optionally to selectively quantify hydrazine in the potential presence of interferants used to alkalize water or resulting from the degradation of hydrazine, such as ethanolamine (NH2 EtOH), morpholine, or ammonia (NH3). The concentrations of NH2EtOH, morpholine, and NH3 can be up to 100 to 200 times higher than that of hydrazine without diminishing the effectiveness and accuracy of the detection method according to the invention.

[0008] The reagent used also reacts simultaneously with these other amines, forming colored compounds distinct from the compound formed with hydrazine. The method therefore also allows for the detection and determination of the concentration of ethanolamine or morpholine at the same time as that of hydrazine, which can be used, for example, to verify the proper alkalinization of the water.

[0009] Furthermore, the detection and quantification of hydrazine may need to be carried out in both the water and air compartments, and the process according to the invention allows this.

[0010] In the water compartment, samples for analysis must be taken without loss of material due to the volatility of the target compound (N2H4) and that of the interfering compounds (NH3, NH2EtOH, morpholine) for in situ analysis or delayed analysis in the laboratory after 24 hours. The analytical method must be selective for N2H4, the concentration of which is up to 100 to 200 times lower than that of the interfering compounds. The concentration range of N2H4 in the water compartment can be wide, from 0.2 to 200 pg-L (i.e., from 0.2 to 200 ppb).

[0011] In the air compartment, the ambient air sample is taken, which, in addition to oxygen (O2), water vapor, and VOCs (Volatile Organic Compounds), also contains other nitrogen compounds (N2H4, NH3, NH2EtOH, morpholine). One of the objectives is therefore to selectively measure gaseous hydrazine over a wide concentration range, from 1.3 to 264 pg-m3 (i.e., from 1 to 200 ppb), and also to quantify the nitrogen interfering potentials. The analysis must be feasible in situ or delayed in the laboratory after 24 hours.

[0012] The detection of hydrazine has been the subject of much research, and the detection methods are as numerous as they are varied due to the high chemical reactivity of this compound. However, most of the research focuses either on measuring hydrazine in water or in air. Methods that allow detection in both water and air compartments are rare, or even unexplored.

[0013] Therefore, in the following prior art description, the water and air compartments are treated separately, and only methods proposed in the literature capable of covering the desired concentration ranges in the water and air compartments are described, namely from 0.2 to 200 pg-L (i.e., from 0.2 to 200 ppb) and 1.3 to 264 pg-m3 (i.e., from 1 to 200 ppb), respectively. Prior art

[0014] Detection of hydrazine in water

[0015] Since hydrazine is both a powerful reducing agent, a good nucleophile and a base, detection can then be obtained by its nucleophilic, reducing or basic property.

[0016] Nucleophilic detection is the most studied method and relies primarily on nucleophilic substitution reactions on a carbonyl group of an aromatic aldehyde, forming a colored absorbing and / or fluorescent product. Para-dimethylaminobenzaldehyde (pDMAB) is the most commonly used method industrially. Para-dimethylaminobenzaldehyde reacts with hydrazine in acidic media, leading to an addition compound, p-dimethylaminobenzalazine, which absorbs in the visible range with a maximum centered at 458 nm or 454 nm, depending on the surrounding medium. The molar extinction coefficient of p-dimethylaminobenzalazine is high, around 60,000 L-mol / L⁻cm¹ [12>3], and the detection limit of hydrazine with this reagent is 4.7 pg / L⁻¹ when the assay is performed with a spectrophotometric cuvette with a 5 cm optical path length.Since p-Dimethylaminobenzalazine is unstable, its detection is time-limited, and it is not possible to perform delayed measurements beyond 16 hours. Based on this method, several teams have modified the reaction to improve the hydrazine detection procedure and / or sensitivity.

[0017] George et al. [4] improved sensitivity by producing 2,4-dinitrophenylhydrazine in situ by first reacting hydrazine with 2,4-dinitrochlorobenzene in the presence of sodium acetate and diethylene glycol. Since 2,4-dinitrophenylhydrazine is an excellent reagent for the detection and quantification of carbonyl groups, it then reacts with pDMAB in an acidic medium to form a yellow hydrazone. The hydrazone, which absorbs at 458 nm, has a very high molar extinction coefficient (e458nm ~ 81000 L-mol / L'-cm1), thus increasing the sensitivity of the measurement. However, this method uses a reprotoxic and carcinogenic compound, 2,4-dinitrochlorobenzene. Furthermore, the method is lengthy and complex because the detection procedure involves five successive steps that are difficult to implement in situ: 1) Formation of 2,4-dinitrophenylhydrazine by heating the mixture until the volume is reduced to half the initial volume

[0018] 2) Reaction of 2,4-dinitrophenylhydrazine with pDMAB

[0019] 3) Cooling the mixture to room temperature

[0020] 4) Formation of the final product by adding HCl

[0021] 5) Determination of the final product by UV-visible at 458 nm.

[0022] In the study by Ortega-Barrales et al. [5], sensitivity is improved with the assay of the colored product (benzalazine) in solid phase; a Dowex ion-exchange resin 5OWx8 is added to the reaction medium to trap and concentrate the benzalazine. The benzalazine then binds to the Dowex beads by centrifugation. The resin is subsequently recovered by filtration, and the benzalazine adsorbed onto the transparent resin is quantified in the solid phase by spectrophotometry at 464 nm. The detection limit is approximately 0.016 pg-L per liter of sample. While highly sensitive, this method is difficult to adapt for field use due to its technical complexity.

[0023] Other substituted benzaldehydes have also been studied for the determination of hydrazine such as vanillin [6], veratraldehyde [7], 2-hydroxy-l-naphthaldehyde [8] and 5-Nitro-2-furaldehyde [9]. These four probe molecules are less reactive than pDMAB and the reactions were produced at high temperature.

[0024] In recent years, several teams have developed selective hydrazine detection methods based on fluorescent probes to determine primarily the presence of hydrazine in drinking water, raw water (rivers, etc.), and especially in living cells. The fluorescent probes are generally aromatic polycyclic molecules with one or two electrophilic sites capable of reacting with hydrazine.

[0025] Roy et al.

[10] and Nguyen et al. [n] have published reviews on the various fluorescent probes used for hydrazine detection. Using fluorescent probes, it is possible to achieve low limits for hydrazine concentration in water in the ng-L range*. The best sensitivities achieved are 35 ng-L

[12] , 60 ng-L [n], 280 ng-L

[14] , and 300 ng-L

[15] in water. However, the main drawback of fluorescent probes is their availability. Indeed, none of the proposed probes are currently commercially available. Furthermore, the authors do not mention any stability studies of the additive products formed.

[0026] Other methods are based on the reducing property of hydrazine in acidic media. Afkhami et al.

[16] proposed an indirect method for the detection of hydrazine in solution based on the inhibition of the redox reaction between the bromate ion and hydrochloric acid. In acidic media, the bromate ion (BrO3) is reduced by the chloride ion (CE) to Br2. Chlorine and bromine are then measured by the decolorization of methyl orange, which absorbs at 525 nm. The presence of hydrazine inhibits the decolorization of methyl orange. Indeed, since hydrazine is a strong reducing agent, it reacts rapidly with chlorine and bromine to form CE and Br ions. The decolorization rate is reduced in the presence of hydrazine. This method allows linear determination of 9.6 to 1024 pg-L 1 of hydrazine, with a limit of detection of 2.72 pg-L *.

[0027] Methyl orange can be replaced by Victoria blue 4R

[17] to obtain similar sensitivity. However, interference exists; NH3, interferes with Hydrazine is reactive towards Cl2 and Br2, which makes the method non-selective.

[0028] Hydrazine can also reduce chloroauric acid (HAuC14) molecules, inducing the formation of gold nanoparticles, AuNPs, which are stable in the presence of sulfamic acid and whose resonance plasmon is detected in the visible range. Gao et al.

[18] exploited this method by monitoring the growth of AuNPs, whose size increases with the hydrazine concentration. The solution, initially colorless, turns red and then blue as the hydrazine concentration increases. Monitoring the absorbance at 540 nm allows the detection of hydrazine over a wide concentration range from 3.2 to 8096 pg-L A with a limit of detection of 2.72 pg-L '.Modifications to this method have been made by different teams by replacing sulfamic acid with different stabilizers such as sodium dodecyl sulfate

[19] , dipicolinic acid

[20] or sodium citrate

[21] in order to improve sensitivity. The latter shows interesting sensitivity, with a detection limit of 3.2 x 10⁵ pg-L, but with a very limited measurement range extending only between 3.2 x 10⁴ and 3.2 pg-L.

[0029] The same principle was adopted by Tashkhourian et al.

[22] who proposed the detection of hydrazine from the plasmon resonances of silver nanoparticles at 415 nm. Hydrazine reduces AgNO3 to silver nanoparticles in the presence of a stabilizer such as polyvinylpyrrolidone or dodecyldimethylammonium chloride. This method allows the individual detection of hydrazine, phenylhydrazine, and isoniazid, with detection limits of 3.84 pg-L (hydrazine), 13 pg-L (phenylhydrazine), and 16.4 pg-L (isoniazide), respectively, but is not selective.

[0030] Of all the methods for measuring hydrazine in water listed, only the one using p-dimethylaminobenzaldehyde (pDMAB) is selective for hydrazine and can be used at room temperature within the target hydrazine concentration range. This method is indeed used industrially, but the protocol specifies a measurement window of 16 hours, after which the colored product, benzalazine, degrades. Therefore, using this method with a 24-hour delayed measurement is not possible. Furthermore, this method does not allow for the detection and quantification of interferents such as NH2EtOH or morpholine because the reaction products, if formed, would absorb in the UV range in an area where the absorbance is saturated by that of pDMAB alone.

[0031] Detection of hydrazine in the air

[0032] Methods for measuring hydrazine in air are less numerous than those for the liquid phase, particularly in the targeted range of 1.3 to 264 pg-m3 (i.e., 1 to 200 ppb). The current measurement method is described in INRS Fact Sheet 21. It is based on the use of benzaldehyde

[23] . Hydrazine is collected by aspirating air through a tube filled with an inert adsorbent (Chromosorb P NAW or (equivalent) of particle size 3060 Mesh, impregnated with sulfuric acid. The cartridge contents are desorbed with deionized water and derivatized with benzaldehyde. The addition compound, benzalazine, is measured by high-performance liquid chromatography (HPLC) coupled with UV optical detection [24, 25]. This method allows the detection of 30 ppb of hydrazine in 15 minutes of sampling. A variant of this method uses a cassette containing two glass fiber filters impregnated with sulfuric acid. Hydrazine is extracted with an EDTA buffer solution and derivatized with benzaldehyde. The benzalazine formed is measured by HPLC coupled with UV optical detection

[26] . This assay method proves sensitive, as it is possible to detect 0.017 ppb of N2H4.These two methods do not allow for direct on-site measurement, and the interference of high concentrations of NH3 or other amines, 50 to 100 times greater than that of hydrazine, is unknown.

[0033] Direct measurement methods are also available. For monitoring worker exposure to hydrazine, monomethylhydrazine (MMH), and 1,1-dimethylhydrazine (UDMH), used as rocket fuels at air bases and space centers in the United States, several colorimetric dosimeters have been developed and marketed by laboratories [27, 28]. The principle is based on incorporating an aromatic aldehyde such as vanillin, para-dimethylaminobenzaldehyde (pDMAB), or 2,4-dinitrobenzaldehyde onto filter paper or an inert surface. Hydrazine and MMH react with vanillin or 2,4-dinitrobenzaldehyde to form a yellow compound, while the product formed with pDMAB is orange. UDMH reacts with 2,4-Dinitrobenzaldehyde to form a yellow-colored compound and there is no reaction with vanillin and pDMAB.Colorimetric dosimeters based on vanillin and para-dimethylaminobenzaldehyde are marketed by DODTEC

[29] and CHEMSEE

[30] . They allow the estimation of hydrazine and monomethylhydrazine concentrations in air in the range of 0.025 to 1.2 ppm.

[0034] In US patent 005719061A

[31] , Rose-Pehrsson et al. propose a method for the selective detection and quantification of liquid or gaseous hydrazine, monomethylhydrazine, and 1,1-dimethylhydrazine by derivatization with aromatic carboxyaldehydes and fluorimetric analysis. The selectivity is based on the reactivity of three derivatizing agents—orthophthalaldehyde (OPA), naphthalene 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 have therefore developed a complex device that pumps ambient air through a reagent solution whose com The position (OPA, NDA, or AD A) and pH must be adjusted to achieve selectivity. Even though the detection limit is on the order of ppb, analyzing the gaseous mixture requires numerous steps involving changing reagents and pH, followed by fluorimetric analyses. Furthermore, there is no study of interferences, particularly with other amines at concentrations 50 to 100 times higher, which could alter the solution's pH.

[0035] For precise measurements, several commercial devices are available. The InterScan portable electrochemical detector, model 4180-100b

[32] , can detect hydrazine in a narrower range from 0 to 100 ppb in less than 1 second, with a detection limit of 10 ppb. However, the method is not selective because the sensor also detects NH3, NOx, CO, and other organic amines.

[0036] High sensitivity can also be achieved using instruments equipped with a photoionization detector (PID) such as the ppbRAE 3000 from RAE

[33] . The photoionization detector, equipped with a 10.6 eV lamp, ionizes hydrazine and measures a few ppbs in 3 seconds. However, the detection is not selective because a large number of volatile organic compounds present in the air with an ionization potential below 10.6 eV are also detected, such as NH3, ethanolamine, and morpholine.

[0037] Ionization of hydrazine followed by ion mobility measurement using ion mobility spectrometry (IMS) allows for concentrations on the order of tens of ppb (20–30 ppb) while being selective with the choice of carrier gas

[38] . When using a radioactive source, the IMS (such as the SABRE 4000 portable detector

[34] or the ChemProlOOi from Environics

[35] ) must be operated by a qualified radiation protection expert. This technique is preferred by the armed forces and police for the detection of chemical weapons and illicit substances. 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 MaSaTECH

[36] or LCD 3.3 from Smiths Detection

[37] .

[0038] The state of the art in hydrazine measurements shows that the only currently existing simple method, using pDMAB as a reagent, can be used in the water compartment with good selectivity and sensitivity. However, the benzalanine formed in solution is unstable after 16 hours, and the measurement cannot be performed 24 hours later. For measuring hydrazine in the air compartment, the INRS (National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases) uses benzaldehyde. The method requires adsorption and then desorption steps before analysis, steps which are difficult to perform. feasible in the field. Furthermore, for this method, interference with high concentrations of NH3, ethanolamine or morpholine is not known in either water or air.

[0039] There is therefore a real need for a method of detection and optionally of quantification of hydrazine usable in the water and air compartments, selective for hydrazine, compatible with the potential presence of high concentrations of interfering substances, easy to implement in the field and which allows for delayed measurement of up to at least 24 hours.

[0040] The process according to the invention addresses these problems. Summary

[0041] A first object of the invention is a method for detecting at least one amine-type compound, said compound being selected from hydrazine, ethanolamine, and morpholine, using a reagent composition comprising a mixture of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid, said method comprising the steps of:

[0042] a) mixing said sample to be analyzed with said reagent composition to obtain a mixture consisting of the sample to be analyzed and said reagent composition,

[0043] b) detection of said amine-type compound(s) in the mixture consisting of the sample to be analyzed and said reagent composition.

[0044] Another object of the invention is a composition of reagents comprising a mixture of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid.

[0045] The present invention also relates to the use of a reagent composition comprising a mixture of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid for the detection of at least one amine-type compound, said compound being selected from hydrazine, ethanolamine and morpholine.

[0046] Another object of the invention is a kit for preparing the composition of reagents according to the invention, said kit comprising:

[0047] - a first container comprising 4-(dimethylamino)-cinnamaldehyde;

[0048] - a second container comprising an aqueous solution of polystyrene acid sulfonic. Brief description of the drawings

[0049] Other features, details and advantages will become apparent from reading the detailed description below and from analyzing the accompanying drawings, in which: Fig. 1

[0050] [Fig. 1] shows the scheme of the reaction between N2H4 and 2 molecules of DMACA with the formation of a colored product 2DMACA-N2H4 absorbing in the visible Fig. 2

[0051] [Fig.2] shows the differential spectra obtained at different times showing the evolution of the 2DMACA-N2H4 complex towards its protonated form with the presence of an isobestic absorbance point at 553 nm. The conditions applied were as follows: DMACA 5 x 10 3M + PSS 9.2 gL 1 + N2H4 5.5 x 10 6M, quartz cuvette with optical path length 1 cm. Fig. 3

[0052] [Fig.3] shows the scheme of the reaction between NH2EtOH and DMACA with formation of the NH2EtOH-DMACA complex absorbing at 474 nm. Fig. 4

[0053] [Fig. 4] shows the differential spectra of the reaction between DMACA and NH2EtOH as a function of time. The conditions applied were as follows: DMACA 5 x 10⁻³M + PSS 9.2 gL⁻¹ + NH2EtOH 6.24 x 10⁻⁴M, quartz cuvette with a 1 cm optical path length. Fig. 5

[0054] [Fig.5] shows the scheme of the reaction between morpholine and DMACA with formation of the morpholine-DMACA complex. Fig. 6

[0055] [Fig.6] shows the spectral evolution of the morpholine-DMACA complex as a function of time. The conditions applied were as follows: DMACA 5 x 10 3M + PSS 9.2 gL 1 + morpholine 6.24 x 10 4 M, quartz cuvette with optical path length 1 cm. Fig. 7

[0056] [Fig.7] shows the calibration lines of the absorbance variation of the addition compound 2DMACA-N2H4 as a function of the concentration in [N2H4] between 5 x 107 and 5.5 x 106 M. The conditions applied being as follows: at 553 nm (5 min, isobestic point), at 474 nm at 24h and at 487 nm at 1h, [DMACA] = 5 x 103 M, [PSS] = 9.2 gL 1 i.e. r = [H+] / [DMACA] = 10, optical path length of 1 cm. Fig. 8

[0057] [Fig. 8] shows the calibration curve of the 24H absorbance variation of the DMACA-NH2EtOH addition compound absorbing at 474 nm as a function of the NH2EtOH concentration between 1 x 10⁴ and 2 x 10³ M, at 24H. The conditions applied were as follows: optical path length 1 cm. [DMACA] = 5 x 10³ M, [PSS] = 9.2 g L⁻¹, therefore r = [H⁺] / [DMACA] = 10. Fig. 9

[0058] [Fig. 9] shows the calibration curve of the absorbance variation at 1H of the DMACA-morpholine addition compound absorbing at 487 nm as a function of the morpholine concentration between 5 x 10⁵ and 6.24 x 10⁴ M at 1H. The conditions applied were as follows: optical path length of 1 cm. [DMACA] = 5 x 10³ M, [PSS] = 9.2 g L⁻¹, i.e., r = [H+] / [DMACA] = 10. Fig. 10

[0059] [Fig. 10] shows the measurements of N2H4 in the presence of the interferants (NH3+NH2EtOH or NH3+morpholine) on an industrial site and the comparison of the DMACA / PSS analytical method (with r= 10) with the pDMAB (p-dimethylaminobenzaldehyde or pDMABA) analytical method and amperometric measurements. Fig. 11

[0060] [Fig. 11] shows a repeatability test of measurements of low N2H4 concentrations. The conditions applied were as follows: 60 min of sampling at a flow rate of 1 L-min 1 with bubbling in 50 mL of a reagent solution (DMACA / PSS, r=10); with P=101325 Pa; R=8.3144621 JK '-mol1; T=295 Kelvin. Detailed description

[0061] The present invention relates to a method for detecting at least one amine-type compound in a sample to be analyzed, said compound being selected from hydrazine, ethanolamine, and morpholine, using a reagent composition comprising a mixture of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid, said method comprising the steps of:

[0062] a) mixing said sample to be analyzed with said reagent composition to obtain a mixture consisting of the sample to be analyzed and said reagent composition,

[0063] b) detection of said amine-type compound(s) in the mixture consisting of the sample to be analyzed and said reagent composition.

[0064] In addition to detection, the method according to the invention can also allow the determination, in a sample to be analyzed, of the concentration of at least one amine-type compound, said compound being selected from hydrazine, ethanolamine, and morpholine. Thus, according to a particular embodiment, the present invention relates to a method for detecting and quantifying, in a sample to be analyzed, at least one amine-type compound, said compound being selected from hydrazine, ethanolamine, and morpholine, using a reagent composition comprising a mixture of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid, said method comprising the steps of:

[0065] a) mixing said sample to be analyzed with said reagent composition to obtain a mixture consisting of the sample to be analyzed and said reagent composition,

[0066] b) detection and quantification of said amine-type compound(s) in the mixture consisting of the sample to be analyzed and said reagent composition.

[0067] Advantageously, the method according to the invention allows for the detection and quantification of hydrazine, despite the presence in the sample to be analyzed of interfering substances such as ammonia, ethanolamine, or morpholine. The method according to the invention in this particular embodiment thus offers a real advantage since it provides the possibility of detecting and quantifying these amine-type compounds in a single step.

[0068] In the context of the present invention, quantification means the determination of the concentration of a compound within a sample to be analyzed.

[0069] The method according to the invention can advantageously be applied to a liquid or gaseous sample or an aerosol. The method according to the invention remains identical whether the sample to be analyzed is liquid, gaseous, or an aerosol; only the method of collecting the sample to be analyzed may differ. For the purposes of this invention, a liquid sample is understood to be a sample in the form of a solution or suspension. For the purposes of this invention, an aerosol is understood to be a suspension, in air or in a gas, of solid particles or, more generally, liquids.

[0070] Step b) of detection or of detection and quantification of the process according to the invention can in particular be carried out by measuring over time the absorbance of the mixture consisting of the sample to be analyzed and said composition of reagents. This step b) is thus carried out in solution.

[0071] The advantages of the process according to the invention compared to those currently existing, in particular the one using the pDMAB reagent, are numerous: - It allows for the detection and optional selective quantification of hydrazine (N₂H₄), specifically via the time-dependent absorbance measurement of the addition compound 2DMACA-N₂H₄, whose visible absorption spectrum extends from 460 to 620 nm. These detection and quantification methods are possible and remain reliable despite the presence of high concentrations of interfering compounds compared to the hydrazine concentration in the sample. Thus, the concentrations of interfering compounds can be up to 200 times higher than that of hydrazine without compromising the effectiveness of the hydrazine detection process.

[0072] - In the case of a measurement by absorbance as a function of time (also called colorimetric measurement) of hydrazine in water, this is easy, quick and instantaneous, by taking a determined volume of the solution to be analyzed and mixing it with the reagent solution.

[0073] - In the case of a measurement by absorbance as a function of time, thanks to the existence From an isobestic point of stable absorbance in the absorption spectrum of the addition compound 2DMACA-N2H4, the measurement of hydrazine via the absorbance of the addition complex at this point can be instantaneous or performed with a delay of up to 3 days. This is because the inventors have demonstrated that the isobestic point is stable for at least 3 days. The experimenter can thus obtain an instantaneous measurement of the hydrazine concentration, for example at 5 minutes, and have 3 days, for example, to verify it later if desired. The isobestic point corresponds to a wavelength at which the absorbance is constant during a chemical reaction. Thus, in this case, the chemical reaction involves a starting material (here, 2DMACA-N2H4) and a final product (protonated 2DMACA-N2H4), which have the same absorption coefficient at this wavelength.

[0074] - The measurement of hydrazine in the air is carried out using the same analytical method as When the sample is liquid, the air to be analyzed is drawn at a constant speed and bubbled through the reagent solution for a predetermined time. Due to its high solubility, the gaseous N2H4 contained in the sampled air dissolves instantly in the reagent solution, and the N2H4 concentration is measured from the absorbance of the 2DMACA-N2H4 addition complex at the isobestic point.

[0075] - It allows the concentrations of the interfering substances, ethanolamine (NH2EtOH) to be measured or morpholine, in solution in particular via the measurement of the absorbance as a function of time of the addition compounds DMACA-NH2EtOH or DMACA-morpholine whose absorption spectra differ from that of 2DMACA-N2H4.

[0076] - The quantification of ethanolamine or morpholine present in the air is also possible via their dissolution in the reagent solution and the determination of the absorbance as a function of time of the colored complexes DMACA-NH2EtOH or DMACA-morpholine.

[0077] The analytical method which allows the determination of the contents of hydrazine and of interferants bearing a primary or secondary amine function by absorbance measurements as a function of time involves knowledge of the absorption spectra of the solution of reactants, of the 2DMACA-N2H4 addition complexes and of the addition complexes of DMACA with the interferants which are ethanolamine (NH2EtOH) and morpholine.

[0078] This method of measuring hydrazine in the presence of 2 interfering substances, NH2EtOH + NH3 or morpholine + NH3, advantageously comprises the succession of steps detailed below.

[0079] In aqueous solution, the reaction between hydrazine (N2H4) and 4-(dimethylamino)-cinnamaldehyde (DMACA) catalyzed in the presence of polystyrene sulfonic acid gives rise to the formation of the red-colored 2DMACA-N2H4 addition complex ([Fig.1] and [Fig.2]).

[0080] The presence of polystyrene sulfonic acid is necessary to protonate DMACA and facilitate the addition of N2H4 to DMACA. However, the protonation of N2H4 could also take place in an acidic medium. This reaction would inhibit the formation of 2DMACA-N2H4 addition complex. The amount of acid required for the reaction between N2H4 and DMACA must therefore be chosen to favor this reaction while minimizing the protonation of N2H4.

[0081] The process according to the invention is thus advantageously implemented with a ratio r of the concentrations of polystyrene sulfonic acid and 4-(dimethylamino)-cinnamaldehyde ranging from 1 to 20, preferably from 2 to 15, even more preferably 10.

[0082] This ratio is calculated from the molar concentrations of polystyrene sulfonic acid and 4-(dimethylamino)-cinnamaldehyde (r = [H+] / [DMACA]). For this calculation, the molar mass of the polystyrene sulfonic acid monomer (M = 184 g / mol) is used to convert the mass concentration of polystyrene sulfonic acid (PSS) 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 × 10³ 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.

[0083] Tests carried out with different quantities of PSS acid, 1.84, 3.68, 5.98, and 9.2 g / L, corresponding to ratios r = [H+] / [DMACA] of 2, 4, 6.5, and 10, show that, regardless of the acidity of the medium, an absorbing product at 558 nm, corresponding to the addition compound, 2DMACA-N2H4, is instantaneously formed. Furthermore, the absorbing product at 558 nm evolves towards its protonated form, absorbing at 535 nm, with the appearance of an isobestic point that remains stable for 3 days. The wavelength corresponding to the isobestic point varies with the ratio r and ranges between 553 nm (r = 10) and 538 nm (r = 2).

[0084] The ratio of the concentrations of polystyrene sulfonic acid and 4-(dimethylamino)-cinnamaldehyde can also be expressed with a ratio r' of the mass concentrations of the two species (r1 = [H+] / [DMACA]), this ratio r' ranging from 1 to 20, preferably from 2 to 15, even more preferably 11. For example, with a concentration of DMACA of 5.103 mol.L 1 corresponding to 0.876 gL 1 (with M = 175.23 g.mol ') and a concentration of PSS of 9.2 gL *, the ratio r' is equal to 10.5.

[0085] DMACA also reacts with other amines such as NH2EtOH to give the NH2EtOH-DMACA complex absorbing at 474 nm ([Fig.3] and [Fig.4]).

[0086] Figure 4 shows the formation of the NH₂EtOH-DMACA complex and its evolution over time. The maximum absorption of the complex is located at 474 nm in a region where the 2DMACA-N₂H₄ complex and its protonated form absorb practically nothing. The reaction between DMACA and NH₂EtOH is much slower than between DMACA and N₂H₄. For the determination of the NH₂EtOH concentration, the time factor is taken into account for the calibration curve.

[0087] In the presence of morpholine, the morpholine-DMACA addition compound is formed and absorbs at 487 nm ([Fig. 5]). The rate of formation of morpholine-DMACA is faster than that of ethanolamine-DMACA. The absorbance at 487 nm reaches a plateau after 1 hour ([Fig. 6]).

[0088] According to a particular embodiment, the detection or detection and quantification method according to the invention can be implemented according to the following steps: 1. Preparation of the reagent solution by mixing DMACA and PSS in water; 2. Establishment of calibration curves of N2H4 from the absorbance of the addition complex 2DMACA-N2H4 at given wavelengths, for example at the isobestic point at 553 nm, at 487 nm (t=1H) and at 474 nm (t=24H); 3. Establishment of the calibration curve of other amine-type compounds (interfering) at given wavelengths, for example 474 nm for ethanolamine and 487 nm for morpholine; 4. Preparation of the sample to be analyzed by mixing the reagent solution and the sample taken; 5. Measurement of the absorbance of the sample to be analyzed as a function of time (for example at 5 min, 1 hour and 24 hours); 6. Calculation of the concentrations of N2H4 and other amine-type compounds (interfering) from the absorbance spectra as a function of time of the sample to be analyzed and the equations of the calibration curves previously obtained.

[0089] According to a particular embodiment, the method for detecting and quantifying N2H4 and NH2EtOH (or morpholine) in water according to the invention can be carried out by following these steps:

[0090] 1. Preparation of the reagent solution by mixing defined quantities of DMACA and PSS in water. A stock solution of reagents is then obtained with known final concentrations of DMACA and PSS and a ratio r of these concentrations = [H+] / [DMACA] also defined.

[0091] 2. Establishment of the calibration curves of N2H4 from the absorbance of the addition complex 2DMACA-N2H4 at the isobestic point at 553 nm, at 487 nm (t=1H) and at 474 nm (t=24H)

[0092] The calibration curves of N2H4 are prepared by adding a volume x (for example 5 mL) of solution containing varying concentrations of N2H4, in the range of 5 x 107 to 5.5 x 106 mol-L*, to the same volume x of the reagent solution prepared in step 1. The solutions obtained are studied by UV-visible spectrophotometry between 5 min and 24H using a quartz cell with a 1 cm optical path length.

[0093] The calibration curves are established at different wavelengths ([Fig. 7]): 553 nm (isobestic point), 474 nm (NH2EtOH absorption peak) at 24H and 487 nm (peak (absorption of morpholine) at 1H. Plotting the lines corresponding to the time evolution of absorbance as a function of N2H4 concentration allows us to obtain, by linear regression, the following equations: - At the isobestic point, Abs ((2DMACA-N2H4) at 553 nm) = A [N2H4]

[0094] - At 474 nm and at 24H, Abs ((2DMACA-N2H4) at 474 nm, 24H) = A! [N2H4]

[0095] - At 487 nm and at 1H, Abs ((2DMACA-N2H4) at 487 nm, 1H) = A2 [N2H4],

[0096] 3. Establishment of the calibration curve of the NH2EtOH interference or morpholine

[0097] 3.a. Establishment of the calibration curve of the NH2EtOH interference from of the absorbance measurement of the DMACA-NH2EtOH complex at the absorption peak at 474 nm

[0098] The calibration curve of NH2EtOH is carried out by adding a volume x (for example 5 mL) of solution containing varying concentrations of NH2EtOH, in the range of 1 x 10⁴ to 2 x 10³ mol-L*, in the same volume x of the reagent solution prepared in step 1.

[0099] The calibration curve of the DMACA-NH2EtOH addition compound is obtained by measuring the absorbance at 474 nm over 24 hours using a quartz cell with a 1 cm optical path length. Plotting the line corresponding to the evolution of the absorbance over 24 hours as a function of the NH2EtOH concentration allows us to obtain, by linear regression, the following equation: Abs ((DMACA-NH2EtOH) at 474 nm and 24H) = B [NH2EtOH] ([Fig.8]).

[0100] 3.b. Establishment of the calibration curve of the morpholine interferent at starting from the absorbance measurement of the DMACA-morpholine complex at the absorption peak at 487 nm.

[0101] The morpholine calibration curve is made by adding a volume x (for example 5 mL) of solution containing varying concentrations of morpholine, in the range of 5 x 105 to 6.24 x 104 mol-L*, in the same volume x of the reagent solution prepared in step 1.

[0102] The calibration curve of the DMACA-morpholine addition compound is obtained by measuring the absorbance at 487 nm, at 1H, using a quartz cell with a 1 cm optical path length. Plotting the line corresponding to the evolution of the absorbance at 1H as a function of the morpholine concentration allows us to obtain, by linear regression, the following equation:

[0103] Abs ((DMACA-morpholine) at 487 nm and 1H) = C [morpholine] ([Fig.9]).

[0104] 4. Sampling

[0105] The sampling of the sample to be analyzed, containing N2H4 and NH2EtOH (or N2H4 and morpholine), is carried out as follows:

[0106] - In a volumetric flask, a volume x (for example 5 mL) of the solution is introduced

[0107]

[0108]

[0109]

[0110] [YES]

[0112]

[0113]

[0114]

[0115]

[0116]

[0117]

[0118]

[0119] of reagents, then the same volume x of sample to be analyzed. Since the actual concentrations of the analytes have thus been diluted by half in this mixture whose absorbance will be measured, it is necessary to take this dilution into account by a coefficient of 2 when calculating the concentrations. - The absorption spectrum of the mixture composed of the reagent solution and the sample to be analyzed is collected between 400 and 700 nm at 5 min and at 24 h when the interfering agent is NH2EtOH - The absorption spectrum of the mixture composed of the reagent solution and the sample to be analyzed is collected between 400 and 700 nm at 5 min and at 1H when the interferent is morpholine. 5. Calculations 5.a. The calculation of the concentration of N2H4 in the mixture containing N2H4 and NH2 EtOH (or morpholine) is as follows: The absorbance (Abs) of the addition compound 2DMACA-N2H4 is measured at the isobestic point of 2DMACA-N2H4 and protonated 2DMACA-N2H4, at 553 nm when r= 10. The concentration of N2H4 in the sample in mol-L is deduced using the calibration curve previously established at the isobestic point Abs ((2DMACA-N2H4) at 553 nm) = A [N2H4], according to the equation: ki tj 1 Abs((2DMÂCA-N2H4) at 553 nm) ~ “ Â ~ 5.b. When the interfering compound is NH2EtOH, the calculation of the concentration of NH2EtOH in the mixture containing N2H4 and NH2EtOH is as follows: From the concentration of N2H4 obtained in 5.a., the absorbance of 2DMACA-N2H4 at 474 nm and at 24H is obtained from the calibration curve Abs ((2DMACA-N2H4) at 474 nm, 24H) = Ai [N2H4], obtained in 2. The absorbance of DMACA-NH2EtOH in the mixture at 24 hours is deduced: Abs ((DMACA-NH2EtOH) at 474 nm) = Abs ((mixture) at 474 nm) - Abs ((2DMACA-N2H4) at 474 nm) The concentration of NH2EtOH in mol-L 1 of the sample is deduced from the calibration curve Abs (DMACA-NH2EtOH) = B [NH2EtOH] obtained in 3.a. ([Fig.8]): , _ 1 _ Abs((DMACA-NH.EtOH) « 474 nm} 5.c. When the interfering agent is morpholine, the calculation of the concentration of morpholine in the mixture containing N2H4 and morpholine is as follows: From the concentration of N2H4 obtained in 5.a., the absorbance of 2DMACA-N2H4 at 487 nm at 1H is obtained from the calibration curve Abs ((2DMACA-N2H4) at 487 nm, 1H) = A2 [N2H4], obtained in 2. ([Fig.7]). The absorbance of DMACA-morpholine in the mixture at 1H is deduced:

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[0121]

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[0123]

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[0125]

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[0127]

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[0129]

[0130] Ab s ((DMACA-morpholine) at 487nm) = Ab s ((mixture) at 487nm) - Ab s ((2DMACA-N2H4) at 487nm, 1H) The concentration of morpholine in mol-L1 of the sample is deduced from the calibration curve Abs (DMACA-morpholine) = C [morpholine] obtained in 3.b. ([Fig.9] ): [ it 1 -i {Abs) at 487 nm morpholm = 2i—--- According to another particular embodiment, when the sample to be analyzed is a gaseous sample, the steps of the process for detecting and quantifying N2H4 and NH2EtOH (or morpholine) according to the invention can be identical to those described above for a liquid sample. However, the process for detecting and quantifying gaseous N2H4 and NH2EtOH (or morpholine) requires an additional step compared to the same process applied to a sample in aqueous solution. This additional step consists of collecting the ambient air to be analyzed and bubbling it through the mixture of liquid reagents. Thus, the sampling step can be carried out as follows: the air to be analyzed is pumped at a known flow rate (e.g., IL-min') through a bubbler filled with a known volume (e.g., 50 mL) of the DMACA and PSS reagent mixture. After one hour, the solution is collected for spectrophotometric analysis. The spectrum of the mixture is then collected between 400 and 700 nm at 5 min and after 24 h when the interferent is NH2EtOH. The spectrum of the mixture is collected between 400 and 700 nm at 5 min and after 1 h when the interferent is morpholine. A subsequent calculation step determines the concentrations of N2H4 and NH2EtOH (or morpholine) dissolved in the reagent. To find the concentrations of these analytes in the gas mixture, the total volume of gas pumped (for example, at a flow rate of IL-min') over 1 hour must be taken into account. 5'.a. The calculation of the concentration of N2H4 in the mixture containing N2H4 and NH2 EtOH (or morpholine) is as follows: The absorbance (Abs) of the addition compound 2DMACA-N2H4 is measured at the isobestic point of the 2DMACA-N2H4 and protonated 2DMACA-N2H4 complexes, at 553 nm when r= 10 The concentration of N2H4 in the sample in mol-L is deduced using the calibration curve previously established at the isobestic point Abs ((2DMACA-N2H4) at 553 nm) = A [N2H4], according to the equation: Kt TJ 1 - Abs ((2DMACA-N2H4) at 553 nm) [^2H4] ~ Â 5'.b. The calculation of the concentration of NH2EtOH in the mixture containing N2H4 and NH2EtOH is as follows:

[0131]

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[0144]

[0145] From the concentration of N2H4 obtained in 5'.a., the absorbance of 2DMACA-N2H4 at 474 nm and at 24H is obtained from the calibration curve Abs ((2DMACA-N2H4) at 474 nm, 1H) = Ai [N2H4], obtained in 2. The absorbance of DMACA-NH2EtOH in the mixture at 24 hours is deduced from: Abs ((DMACA-NH2EtOH) at 474 nm) = Abs ((mixture) at 474 nm) - Abs ((2DMACA-N2H4) at 474 nm) The concentration of NH2EtOH in mol-L 1 of the sample is deduced from the calibration curve Abs((DMACA-NH2EtOH) at 474 nm) = B [NH2EtOH] obtained in 3.a.: NHÆtOH = Abs (DMACA-NH,EtOH) at 474 nm 5'.c. When the interferent is morpholine, the calculation of the concentration of morpholine in the mixture containing N2H4 and NH2EtOH is as follows: From the concentration of N2H4 obtained in 5'.a., the absorbance of 2DMACA-N2H4 at 487 nm at 1H is obtained from the calibration curve Abs ((2DMACA-N2H4) at 487 nm) = A2 [N2H4], obtained in 2. The absorbance of DMACA-morpholine in the mixture at 1H is deduced: Abs ((DMACA-morpholine) at 487nm) = Abs ((mixture) at 487nm) - Abs ((2DMACA-N2H4) at 487nm) The concentration of morpholine in mol-L of the sample is deduced from the calibration curve Abs(DMACA-morpholine at 487 nm) = C [morpholine] obtained in 3.b.: F ii-l Abs (DMACA-morpholine) at 487 nm) morpholm = —1---------- 5'.d. The concentration of N2H4 (or NH2EtOH or morpholine) in the gas mixture in ppb is deduced according to the equation: FZ* 1 ( 1 J ' 7 number of moles of air With : • i = N2H4, NH2EtOH, or morpholine • number of moles of i = [iJmol-L ^V (V = volume of the reactant solution = for example 50 x 103 L) • [number of moles of air] = ™ (D = air flow rate = for example 1 L-min *, t (sampling duration = 1 hour, Vm = molar volume of air = 24.21 L-mol1 at 22°C) In addition to the detection method as defined above, the present invention also relates to a reagent composition comprising a mixture of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid. This composition advantageously allows detection in a medium comprising a compound of the type amine, for example hydrazine, ethanolamine or morpholine, the reaction between the amine-type compound and 4-(dimethylamino)-cinnamaldehyde, this reaction being catalyzed by polystyrene sulfonic acid and giving rise to the formation of an addition complex having absorbance properties in the UV-visible range.

[0146] The reaction between the amine-type compound and 4-(dimethylamino)-cinnamaldehyde (DMACA) is advantageously catalyzed by a polymer-derived acid, in particular polystyrene sulfonic acid. The choice of this type of acid, and in particular polystyrene sulfonic acid, has many advantages. First, this acid is a high molecular weight polymer that has an SO3H acid group for each styrenic monomer. Therefore, the number of available protons is particularly high, allowing the acidity of the solution to be adjusted to catalyze the reaction between DMACA and N2H4. Furthermore, inorganic acids and low molecular weight organic acids have the disadvantage of potentially releasing acid vapor during the bubbling step of the gas mixture to be analyzed, as the acid is therefore likely to evaporate during bubbling. This disadvantage is not present for acids derived from a polymer, such as polystyrene sulfonic acid, because these are not volatile.

[0147] One of the major advantages of this reagent composition is its stability over time, which can last up to at least one week. This stability was demonstrated by the inventors by measuring the absorbance spectrum of the reagent composition up to one week after its preparation. The spectrum obtained was identical to that obtained immediately after the composition was prepared. The composition can therefore be prepared and stored for this period without its effectiveness in the process according to the invention being impaired.This feature advantageously eliminates the need to prepare the reagent composition before each sample analysis process.

[0148] According to a particular embodiment, the composition according to the invention is characterized by a particular ratio r of the concentrations of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid, this ratio ranging from 1 to 20, preferably from 2 to 15, even more preferably 10.

[0149] The present invention also relates to the use of a reagent composition according to the invention for the detection of at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine and morpholine.

[0150] According to a particular embodiment, the invention also relates to the use of a reagent composition according to the invention for the quantification of at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine and morpholine.

[0151] The use according to the invention can advantageously be carried out on a sample

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[0158]

[0159] liquid, gaseous, or aerosol. Another object of the present invention is a kit for preparing a reagent composition according to the invention, said kit comprising: - a first container containing 4-(dimethylamino)-cinnamaldehyde; - a second container containing an aqueous solution of polystyrene sulfonic acid. The kit according to the invention advantageously allows the preparation of the reagent composition according to the invention for use in the process according to the invention. This preparation is particularly simple and quick to carry out since it only requires the mixing of two compounds in water. Examples Compounds used - 4-(Dimethylamino)cinnamaldehyde (DMACA, Sigma-Aldrich, Ref: D4506-5g, lot: BCBX0916, CAS: 6203-18-5, purity >98%, Molar mass = 175.23 g / mol), - Polystyrene sulfonic acid at 18% in water (PSS, Sigma-Aldrich, Ref: 561223-100G, lot: MKBV7207V, CAS: 28210-41-5, Molar mass ~ 75,000 g / mol, density = 1.11 g / mL at 25°C), - Hydrazine hydrate at 50-60% in water (N2H4, Sigma-Aldrich, Ref: 225819-100mL, lot: BCCC1556, CAS: 10217-52-4, Molar mass = 32.05 g / mol, density = 1.029 g / mL at 25°C), - Ethanolamine (NH2EtOH, Sigma-Aldrich, Ref: 398136-500ML, lot: STBJ4500, CAS: 141-43-5, purity >98%, Molar mass = 61.08 g / mol, density = 1.012 g / mL at 25°C), - Morpholine (Sigma-Aldrich, Ref: 252360-100ML, lot: MCKM6935, CAS: 110-91-8, purity >99%, Molar mass = 87.012 g / mol, density = 0.996 g / mL at 25°C), - 28% aqueous ammonia solution (NH3, VWR, Ref: 21182.94, lot: 15J260522, CAS: 1336-21-6, Molar mass = 17.03 g / mol, density = 0.89 g / mL), - Milli-Q® deionized water. Example 1: Protocol for the titration of N2H4 and NH2EtOH (or morpholine) in aqueous solutions with the reagent solution containing [DMACA] = 5 x 10³ M, [PSS] = 9.2 g-L, i.e., r = [H+] / [DMACA] = 10 The determination of N2H4 and NH2EtOH (or morpholine) in water is carried out as follows: 1) Preparation of the reagent solution: In a 50 mL volumetric flask containing 25 mL of water are introduced, along with 87.62 mg of DMACA and 4.604 mL of 18% PSS. Water is added up to the calibration mark, and the solution is sonicated in an ultrasonic bath for 30 minutes to thoroughly dissolve the DMACA. A stock solution of reagents is obtained with final concentrations of DMACA and PSS of 0.01 M and 18.4 g L*, respectively. The ratio r = [H+] / [DMACA] = 10.

[0160] 2) Establishment of calibration curves of N2H4 from the absorbance of addition complex 2DMACA-N2H4 at the isobestic point at 553 nm, at 487 nm (t=1H) and at 474 nm (t=24H), for r = [H+] / [DMACA] = 10)

[0161] a) The calibration curves of N2H4 are prepared by adding 5 mL of solution containing varying concentrations of N2H4, in the range of 5 x 10⁷ to 5.5 x 10⁶ mol⁻¹*, to 5 mL of reagent solution prepared in step 1). The solutions are studied by UV-visible spectrophotometry between 5 min and 24 h using a quartz cell with a 1 cm optical path length. The calibration curves are established at different wavelengths ([Fig. 7]): 553 nm (isobestic point), 474 nm (NH2EtOH absorption peak) at 24 h and 487 nm (morpholine absorption peak) at 1 h: - At the isosbestic point, Abs (553 nm) = Ax = 29110 [N2H4] At 474 nm and at 24H, Abs (474 ​​nm, 24H) = A1X = 7080 [N2H4] At 487 nm and 1H, Abs (487 nm, 1H) = A2x = 7810[N2H4] 3) Establishment of the calibration curve of the NH2EtOH or morpholine interferent

[0162] a) Establishment of the calibration curve of the NH2EtOH interferent from the absorbance measurement of the DMACA-NH2EtOH complex at the absorption peak at 474 nm at 24H

[0163] The calibration curve of NH2EtOH is prepared by adding 5 mL of solution containing varying concentrations of NH2EtOH, in the range of 1 x 10⁴ to 2 x 10³ mol⁻¹*, to 5 mL of the reagent solution prepared in step 1). The calibration curve of the addition compound DMACA-NH2EtOH is prepared by measuring the absorbance at 474 nm, at 24 hours with a quartz cell with a 1 cm optical path length.

[0164] Abs (DMACA-NH2EtOH) at 474 nm and 24H = Bx = 117 [NH2EtOH] ([Fig.8]).

[0165] b) Calibration curve of the morpholine interference from the absorbance measurement of the DMACA-morpholine complex at the absorption peak at 487 nm.

[0166] The morpholine calibration curve is prepared by adding 5 mL of solution containing varying concentrations of morpholine, in the range of 5 x 10⁵ to 6.24 x 10⁴ mol-L⁻¹, to 5 mL of the reagent solution prepared in step 1). The calibration curve of the DMACA-morpholine addition compound is prepared by measuring the absorbance at 487 nm, at 1H with a quartz cell with a 1 cm optical path length.

[0167] Abs (DMACA-morpholine) at 487 nm and 1H = Cx = 488 [morpholine] ([Fig.9]).

[0168] 4) Sampling

[0169] The sampling of the solution to be analyzed, containing N2H4 and NH2EtOH (or N2H4 and morpholine), is carried out as follows: • In a 10 mL volumetric flask, 5 mL of the reagent solution is introduced, followed by 5 mL of the sample to be analyzed. Since the actual concentrations of the analytes have been diluted by half in the mixture, this dilution must be taken into account when calculating concentrations. • The absorption spectrum of the mixture is collected between 400 and 700 nm at 5 min and at 24 h when the interfering agent is NH2EtOH • The absorption spectrum of the mixture is collected between 400 and 700 nm at 5 min and at 1 h when the interferent is morpholine 5) Calculations

[0170] a) The calculation of the concentration of N2H4 in the mixture containing N2H4 and NH2EtOH (or morpholine) is as follows: - Absorbance (Abs) of the addition compound 2DMACA-N2H4 at the isobestic point, 553 nm. - The concentration of N2H4 in the sample in mol-L1 is deduced using the calibration curve previously carried out at the isobestic point Abs (553 nm) = Ax = 29110 [N2H4], according to the equation: Fm 14 1— Abs C 53nm ) 9 [^2^4]— 29110 z

[0171] b) When the interferent is NH2EtOH, the calculation of the concentration of NH2EtOH in the mixture containing N2H4 and NH2EtOH is as follows: - From the concentration of N2H4 obtained in 5)a), the absorbance of 2DMACA-N2H4 at 474 nm and at 24H is obtained from the calibration curve Abs (2DMACA-N2H4) at 474 nm, 24H = 7080 [N2H4], obtained in 2)a). • The absorbance of DMACA-NH2EtOH in the mixture at 24 hours is deduced: Abs (DMACA-NH2EtOH) at 474 nm = Abs (mixture) at 474 nm - Abs (2DMACA-NH2OH) at 474 nm • The concentration of NH2EtOH in mol-L 1 of the sample is deduced from the calibration curve Abs(DMACA-NH2EtOH) = 117 [NH2EtOH] obtained in 3)a) ([Fig.8]): Ato(DMACA-NH,EfOH)at474nm NH2EtOH =2—--------- Z 11 /

[0172] c) When the interferent is morpholine, the calculation of the concentration of morpholine in the mixture containing N2H4 and morpholine is as follows: - From the N2H4 concentration obtained in 5)a), the absorbance of 2DMACA-N2H4 at 487 nm at 1H is obtained from the calibration curve Abs (2DMACA-N2H4) at 487 nm, 1H = 7810 [N2H4], obtained in 2)a) ([Fig.7]). • The absorbance of DMACA-morpholine in the mixture at 1H is deduced: Abs (DMACA-morpholine) at 487nm = Abs (mixture) at 487nm - Abs (2DMACA-N2H4) at 487nm • The concentration of morpholine in mol-L 1 of the sample, using the calibration curve Abs(DMACA-morpholine) = 488 [morpholine] obtained in 3)b) ([Fig.9]): 1 i. i • 1 (Afrs) at 487 nm | morpholmeI = 2-—---

[0173] Example 2: Protocol for the titration of N2H4 and NH2EtOH in aqueous solutions with the reagent solution containing [DMACA] = 5 x 103 M, [PSS] = 3.68 g-L1, i.e., r = [H+] / [DMACA] = 4

[0174] The protocol is the same as that described previously in Example 1 for the reagent solution containing DMACA and PSS, of which r = [H+] / [DMACA] = 10.

[0175] The calibration curves of N2H4 are established with a reagent solution containing [DMACA] = 5 x 103 M, [PSS] = 3.68 gL *, of which r = [H+] / [DMACA] = 4, at different wavelengths: 542 nm (isobestic point) and 474 nm (NH2EtOH absorption peak):

[0176] - At the isobestic point (at 542 nm), Abs (542 nm) = Ax = 37744 [N2H4]

[0177] - At 474 nm and at 24H, Abs (474 ​​nm, 24H) = Alx = 9599 [N2H4]

[0178] The calibration curve of the addition compound DMACA-NH2EtOH is established at 474 nm, at 24H:

[0179] Abs (DMACA-NH2EtOH) at 474 nm and 24H = Bx = 429 [NH2EtOH]

[0180] Example 3: Protocol for the determination of N2H4 and NH2ETOH (or morpholine) at the gaseous state with the reagent solution containing [DMACA] = 5 x 10³ M, [PSS] = 9.2 g-L1, therefore r = [H+] / [DMACA] = 10

[0181] For the measurement of analytes in the gaseous state, N2H4 and NH2EtOH and gaseous morpholine must be generated and their concentrations calibrated.

[0182] The protocol for the determination of gaseous N2H4 and NH2EtOH (or morpholine) requires an additional step compared to the determination of these same analytes in aqueous solution. This step consists of collecting the ambient air to be analyzed and bubbling it through the liquid reagent.

[0183] The protocol is the same as that described in Example 1 for the quantification of analytes in aqueous solution for steps 1), 2) 3).

[0184] Sampling step 4) is as follows: the air to be analyzed is pumped with a flow rate of IL-min 1 through a bubbler 3.16 cm in diameter and 34 cm in height filled with 50 mL of the reagent solution prepared in step 1). After one hour, the solution is taken for spectrophotometric analysis.

[0185] The spectrum of the mixture is collected between 400 and 700 nm at 5 min and after 24H when the interferent is NH2EtOH.

[0186] The spectrum of the mixture is collected between 400 and 700 nm at 5 min and after 1 hour when the interferent is morpholine.

[0187] Step 5) of the calculations determines the concentrations of N2H4 and NH2EtOH (or morpholine) dissolved in the reagent. To find the concentrations of these analytes in the gas mixture, the total volume of gas pumped at a flow rate of IL-min for 1 h must be taken into account. a. The calculation of the concentration of N2H4 in the mixture containing N2H4 and NH2 EtOH (or morpholine) is as follows: - The absorbance (Abs) of the addition compound 2DMACA-N2H4 at the isobestic point, 553 nm for r = [H+] / [DMACA] = 10. - The concentration of N2H4 in the sample in mol-L1 is deduced using the calibration curve previously carried out at the isobestic point Abs (553 nm) = Ax = 29110 [N2H4], according to the equation: [XT tt 1 Abs(553nm) P2M4j“ 29110 a. The calculation of the concentration of NH2EtOH in the mixture containing N2H4 and NH2EtOH is as follows: - From the concentration of N2H4 obtained in 5)a), the absorbance of 2DMACA-N2H4 at 474 nm and at 24H is obtained from the calibration curve Abs (2DMACA-N2H4) at 474 nm, 1H = 7080 [N2H4], obtained in 2)a) ([Fig.9]). • The absorbance of DMACA-NH2EtOH in the mixture at 24 hours is deduced from: Abs (DMACA-NH2EtOH) at 474 nm = Abs (mixture) at 474 nm - Abs ((2DMACA-NH2EtOH)) at 474 nm • The concentration of NH2EtOH in mol-L 1 of the sample is deduced from the calibration curve Abs(DMACA-NH2EtOH) =117 [NH2EtOH] obtained in 3)a): 1 Abs (DMACA-NH,EtOH) at 474 nm NH2EtOH =------------ I 11 7 a. When the interfering agent is morpholine, the calculation of the concentration of morpholine in the mixture containing N2H4 and NH2EtOH is as follows: - From the concentration of N2H4 obtained in 5)a), the absorbance of 2DMACA-N2H4 at 487 nm at 1H is obtained from the calibration curve Abs (2DMACA-N2H4) at 487 nm, 1H = 7810 [N2H4], obtained in 2)a) ([Fig.9]). • The absorbance of DMACA-morpholine in the mixture at 1H is deduced: Abs (DMACA-morpholine) at 487nm = Abs (mixture) at 487nm - Abs (2DMACA-morpholine) 2H4) at 487nm • The concentration of morpholine in mol-L1 of the sample, using the calibration curve Abs(DMACA-morpholine) = 488 [morpholine] obtained in 3)b) ([Fig. 11]): [ ut 1 (Abs) at 487 nm | morpholine = i--- a. The concentration of N2H4 (or NH2EtOH or morpholine) in the gas mixture in ppb is deduced according to the equation: F (] ( DUb} = number of moles of i 1 J ' number of moles of air

[0188] With: • i = N2H4, NH2EtOH, or morpholine • number of moles of i = [iJmol-L'^V (V = volume of the reactant solution = 50 x 103 L) [number of moles of air] = (D = air flow rate = 1 L-min *, t = sampling time = 1H, Vm = molar volume = 24.21 L-mol1 at 22°C)

[0189] Example 4: Application of the method according to the invention to the determination of N2H4 and NH2EtOH in aqueous solutions containing different concentrations of analytes and in the presence of a strong base, NH3, with 50 [N2H4] < [NH3] < 100 [N2H4]. Reagent solution: [DMACA] = 5 x 103 M, [PSS] = 9.2 g-L1, i.e., r = [H+] / [DMACA] = 10 and the isobestic point at 553 nm.

[0190] Seven examples of application of the method are given here. Mixtures of known concentrations of N2H4, NH2EtOH, and NH3 with different ratios of [NH3] / [N2H4] and [NH2EtOH] / [N2H4] were prepared, and the spectra of the mixtures were collected at 24 hours. These spectra were analyzed by collecting absorbance values ​​at specific wavelengths, 553 and 474 nm, to deduce the concentrations of N2H4 and NH2EtOH. The calculated values ​​are then compared to the theoretical concentration values ​​(Table 1).

[0191] [Tables 1] [NH3] [N2H4] [NH2EtOH] [N2H4] [NH3]xO -4M [N2H4]x 10⁶ M [NH2EtOH]x 10⁴ M Theoretical Calculation 1 (A=+7%) Theoretical Difference (%) Calculation 1 (A=+7%) Theoretical Difference (%) Ex 1 100 100 5.63 5.83 5.63 +3.5 6.42 5.63 +14.1 Ex 2 100 100 4.50 4.49 4.5 +0.3 5.16 4.50 +14.7 Ex 3 100 100 3.38 3.27 3.38 +3.1 2.65 3.38 -21.5 Ex 4 100 100 2.25 2.16 2.25 +4.2 1.64 2.25 -27.1 Ex 5 100 50 4.5 4.31 4.19 +2.7 2.90 2.25 +28.8 Ex 6 50 60 1.75 3.37 3.26 +3.4 2.68 2.10 +27.5 Ex 7 10 80 0.15 1.48 1.4 +5.8 0.97 1.20 -19.2 Table 1: Results of the N2H4 and NH2EtOH assays in the mixture containing NH3, N2H4, and NH2EtOH. [DMACA] = 5 x 10³ M, [PSS] = 9.2 g L⁻¹, therefore r = [H+] / [DMACA] = 10, optical path length 1 cm. Difference = (calculated value - theoretical value) / theoretical value.

[0192] This example demonstrates the very good reliability of the process according to the invention, in particular with regard to the detection and quantification of hydrazine, since very small deviations (less than 6%) are observed between the calculated and theoretical values.

[0193] This example also demonstrates the very good sensitivity of the process with regard to the detection and quantification of hydrazine since the concentrations calculated using the process are very close to the theoretical concentrations despite concentrations of interferents (NH3 or NH2EtOH) up to 100 times greater than that of hydrazine.

[0194] Example 5: Application of the method according to the invention to the determination of N2H4 and morpholine in aqueous solutions containing different concentrations of analytes and in the presence of a strong base, NH3 with [NH3] = 150 [N2H4]. Reagent solution: [DMACA] = 5 x 103 M, [PSS] = 9.2 g-L1, therefore r = [H+] / [DMACA] = 10 and the isobestic point at 553 nm.

[0195] Four examples of application of the analytical method are given here. Mixtures of known concentrations of N2H4, morpholine, and NH3 with ratios of [NH3] / [N2H4] = 100 and [morpholine] / [N2H4] = 100 were prepared, and the spectra of the mixtures were collected at 1H. These spectra were analyzed by collecting absorbance values ​​at specific wavelengths, 553 and 487 nm, to deduce the concentrations of N2H4 and morpholine. The calculated values ​​are then compared to the theoretical concentration values ​​(Table 2). [NH3] (x 104 M) [N2H4] (x 106 M) [morpholine] (x 104 M) Theoretical 4.83 4.66 -3.8 4.36 4.66 +6.5 Ex 1 4.66 3.24 3.26 +0.3 2.92 3.26 +10.4 Ex 2 3.26 1.98 1.86 -6.6 1.85 1.86 +0.3 Ex 3 1.86 0.95 0.932 -2.1 0.934 0.932 -0.2 Ex 4 0.466 4.83 4.66 -3.8 4.36 4.66 +6.5 Table 2: Results of the N2H4 and morpholine assays in the mixture containing NH3, N2H4, and morpholine. [NH3] = [morpholine] = 100 x [N2H4], [DMACA] = 5 x 103 M, [PSS] = 9.2 gL*, optical path length 1 cm. Difference = (calculated value - theoretical value) / theoretical value.

[0196] As with Example 1, this example demonstrates the very good reliability of the process according to the invention, particularly with regard to the detection and quantification of hydrazine, since very small deviations (less than 7%) are observed between the calculated and theoretical values.

[0197] This example also demonstrates the very good sensitivity of the process with regard to the detection and quantification of hydrazine since the concentrations calculated using the process are very close to the theoretical concentrations despite concentrations of interferents (NH3 and morpholine) 100 times greater than that of hydrazine.

[0198] Example 6: Application of the method according to the invention to the determination of N2H4 and NH2EtOH in aqueous solutions containing different concentrations of analytes and in the presence of a strong base, NH3, with [NH3] = [NH2EtOH] = 96.55 [N2H4]. Reagent solution: [DMACA] = 5 x 103 M, [PSS] = 3.68 g-L1, i.e., r = [H+] / [DMACA] = 4 and the isobestic point at 542 nm.

[0199] Four examples of application of the analytical method are given here. Mixtures of known concentrations of N2H4, NH2EtOH, and NH3 with ratios of [NH3] / [N2H4] = 96.55 and [NH2EtOH] / [N2H4] = 96.55 were prepared, and the spectra of the mixtures were collected at 24 hours. These spectra were analyzed by collecting absorbance values ​​at specific wavelengths, 542 nm and 474 nm, to deduce the concentrations of N2H4 and NH2EtOH. The calculated values ​​are then compared to the theoretical concentration values ​​(Table 3). [NH3] (x 10⁴ M) [N2H4] (x 10⁶ M) [NH2EtOH] (x 10⁴ M) Theoretical Calculation (A=±7%) Theoretical Deviation (%) Calculation (24H) (A=±7%) Theoretical Deviation (%) Ex 1 5.84 5.81 6.05 -3.9 4.84 5.84 -17.4 Ex 2 4.78 4.95 4.95 +0.1 3.99 4.78 -16.6 Ex 3 3.72 3.92 3.85 +1.9 3.07 3.72 -17.3 Ex 4 2.66 2.79 2.75 +1.5 2.00 2.66 -24.7

[0200] Table 3: Results of blind assays of NH2EtOH and N2H4 with r = 4 in the mixture containing NH3, N2H4 and NH2EtOH. [NH3] = [NH2EtOH] = 96.55 x [N2H4], [DMACA] = 5 x 103 M, [PSS] = 3.68 gL, therefore r = [H+] / [DMACA] = 4, quartz cell with optical path length 1 cm. Difference = ((calculated value - theoretical value) / theoretical value).

[0201] As with examples 1 and 2, this example demonstrates the very good reliability of the process according to the invention, in particular with regard to the detection and quantification of hydrazine, since very small deviations (less than 4%) are observed between the calculated and theoretical values.

[0202] This example also demonstrates the very good sensitivity of the process with regard to the detection and quantification of hydrazine since the concentrations calculated using the process are very close to the theoretical concentrations despite concentrations of interferents (NH3 and NH2EtOH) nearly 100 times greater than that of hydrazine.

[0203] Example 7: Measurements of N2H4 in aqueous solution in the presence of interfering substances at industrial sites

[0204] Liquid hydrazine measurements were performed on four samples taken from an industrial site. In addition to hydrazine, the samples contained other amines of the type NH2EtOH + NH3 or morpholine + NH3 at varying concentrations. The results of the measurements were systematically compared with the amp- measurements Automated line rometric measurements were performed on the sampled lines and with the pDMAB (p-dimethylaminobenzaldehyde) reagent. Figure 10 illustrates all the results obtained.

[0205] This example demonstrates that the method according to the invention makes it possible to obtain hydrazine concentration results very close to those obtained by the known method using pDMAB. Indeed, concentration differences of less than 2 pg / L are observed between the two methods.

[0206] Example 5: Application of the process according to the invention to the determination of gaseous N2H4 and NH2EtOH in ambient air containing different concentrations of analytes and in the presence of a strong base, NH3, with 85 [N2H4] < [NH3] < 116 [N2H4]. Reagent solution: [DMACA] = 5 x 103 M, [PSS] = 9.2 g-L1, i.e., r = [H+] / [DMACA] = 10.

[0207] Five examples of application of the method are given here. Mixtures of known concentrations of N2H4, NH2EtOH, and NH3 with different ratios of [NH3] / [N2H4] and [NH2EtOH] / [N2H4] were prepared. The air to be analyzed was pumped at a flow rate of IL-min 1 to bubble it through 50 mL of reagent for 1 h. The spectra of the mixtures were collected after 24 h. These spectra were analyzed by collecting the absorbance values ​​at specific wavelengths, 553 and 474 nm, to deduce the concentrations of N2H4 and NH2EtOH. The calculated values ​​were then compared to the theoretical concentration values ​​(Table 4). [NH3] [n2h4] [NH2EtOH] [N2H4] [NH3] ppm [N2H4] ppb [NH2EtOH] ppm Theoretical Calculation (A=±7%) Theoretical (A=±8%) Deviation (%) Calculation (24H) (A=±7%) Theoretical Deviation (%) Ex 1 104 99 1 10.6 9.6 10.8% -0.95 - Ex 2 116 111 5 37.2 43 -13.5% 4.79 4.76 0.6% Ex 3 93 88 5 61.5 54 13.9% 4.35 4.76 -8.6% Ex 4 87 45 18.3 229.8 211 8.9% 9.1 9.52 -4.4% Ex 5 85 81 10 137.7 117 17.7% 9.6 9.52 0.8%

[0208] Table 4: Results of the determination of gaseous N2H4 and NH2EtOH in the mixture containing NH3, N2H4 and NH2EtOH, with 50 mL of reagent containing [DMACA] = 5 x 103 M, [PSS] = 9.2 g-L1 i.e. r = [H+] / [DMACA] = 10, quartz cell with optical path length 1 cm. T° = 22°C. Deviation = (calculated value - theoretical value) / theoretical value.

[0209] This example demonstrates the very good reliability of the process according to the invention applied to a gaseous sample, in particular with regard to the detection and quantification of hydrazine, since small differences (less than 18%) are observed between the calculated and theoretical values.

[0210] This example also demonstrates the very good sensitivity of the process according to the invention applied to a gaseous sample with regard to the detection and quantification of hydrazine since the concentrations calculated using the process are very close to the theoretical concentrations despite proportions of interferents (NH3 or NH2EtOH) up to 100 times greater than that of hydrazine.

[0211] Example 6: Application of the process according to the invention to the determination of N2H4 in ambient air containing different concentrations of gaseous morpholine analytes and in the presence of a strong base, NH3, with [N2H4] < [NH3] < [N2H4]. Reagent solution: [DMACA] = 5 x 103 M, [PSS] = 9.2 g-L1, i.e., r = [H+] / [DMACA] = 10.

[0212] Seven examples of application of the method are given here. Mixtures of known concentrations of N2H4, morpholine, and NH3 with different ratios of [NH3] / [N2H4] and [morpholine] / [N2H4] were prepared on an experimental gas bench. The air to be analyzed was pumped at a flow rate of IL.min⁻¹ to bubble it through 50 mL of reagent for 1 h. The spectra of the mixtures were collected at 1 h. These spectra were analyzed by collecting the absorbance values ​​at specific wavelengths, 553 and 487 nm, to deduce the concentrations of N2H4 and morpholine. The calculated values ​​were then compared to the theoretical concentration values ​​(Table 5). [NH3] [n2h4] [morpholine] [N2H4] [NH3] ppm [N2H4] ppb [morpholine] ppm Theoretical Calculation (A=±7%) Theoretical (A=±8%) Difference (%) Calculation (1H) (A=±7%) Theoretical Difference (%) Ex 1 138 146 9 71 65 9.2% 8.8 9.5 -7.4% Ex 2 138 66 9 71 65 9.2% 4.4 4.3 2.3% Ex 3 109 113 10.8 103.5 99.2 4.3% 11.5 11.2 2.7% Ex 4 76 79 7.5 102.1 99.2 2.9% 7.9 7.8 1.3% Ex 5 164 170 8.3 54.2 50.5 7.3% 8.3 8.6 -3.5% FY 6 99 103 5 52.8 50.5 4.6% 4.6 5.2 -11.5% FY 7 57 46 1.6 32.8 28.3 15.9% 1.1 1.3 -15.4%

[0213] Table 5: Results of the N2H4 assay in the mixture containing NH3, N2H4 and morpholine, with 50 mL of reagent containing [DMACA] = 5 x 103 M, [PSS] = 9.2 g-L1, i.e., r = [H+] / [DMACA] = 10, quartz cell with an optical path length of 1 cm. T° = 22°C. Difference = (calculated value - theoretical value) / theoretical value.

[0214] Like Example 5, this example demonstrates the very good reliability of the process according to the invention applied to a gaseous sample, in particular with regard to the detection and quantification of hydrazine, since small deviations (less than 16%) are observed between the calculated and theoretical values.

[0215] This example also demonstrates the very good sensitivity of the process according to the invention applied to a gaseous sample with regard to the detection and quantification of hydrazine since the concentrations calculated using the process are very close to the theoretical concentrations despite proportions of interferents (NH3 or morpholine) up to 170 times greater than that of hydrazine.

[0216] Example 9: Examples of measurements of N2H4 in the gaseous state at two concentration levels

[0217] Air samples were taken from the headspace of two closed tanks containing a concentrated hydrazine solution. The concentrations of hydrazine in the liquid phase are not precisely known, but are estimated to be 1% by weight.

[0218] The aim of the present experiment is to study the reproducibility of the process according to the invention for the quantification of hydrazine in a gaseous sample, the concentration of hydrazine in this sample not being known.

[0219] The sampling and bubbling time in the reagent solution (DMACA / PSS with r=10) is 1 hour. [N2H4]air (pg / m3) + Standard deviation [N2H4] air (ppb) + Standard deviation Tank No. 1 89 + 13 67 + 10 Tank No. 2 70 + 8 53 + 6 This experiment demonstrates the good reproducibility of the hydrazine quantification process in a gaseous sample since the standard deviations reported in the table above are small.

[0220] In order to evaluate the reproducibility of the method on samples with lower concentrations, 20 samples were taken at a distance of 7 meters from the aforementioned tank No. 1, which was covered with a non-sealing lid. These samples were taken under identical experimental conditions. Hydrazine concentrations of 1.80 ppb were measured. Figure 11 illustrates the distribution of the results obtained across all the samples taken.

[0221] This experiment demonstrates the very good repeatability of the process according to the invention applied to a gaseous sample and with a low concentration of hydrazine since, with the exception of one measurement, all the results show measurement variations of less than 0.5 ppb, which is really minimal. List of documents cited

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[0225] [4] M. George, K.S. Nagaraja, N. Balasubramanian, Spectrophotometric déter mination of hydrazine, Talanta, 75, p. 27-31, 2008.

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[0227] [6] S. Amlathe, V. K. Gupta, Spectrophotometric Détermination of Trace Amounts of Hydrazine in Polluted Water, ANALYST, 113, p. 1481 - 1483, 1988.

[0228] [7] R. Kaveeshwar, V. K. Gupta, A new spectrophotometric method for the déter mination of hydrazine in environmental samples, Fresenius J Anal Chem, 344, p. 114-117, 1992.

[0229] [8] J. Mânes, P. Campillos, G. Font, Extraction - Spectrophotometric Détermination of Hydrazine with 2-Hydroxy-l-NaphthaIdehyde, ANALYSE, 112, p. 1183 - 1184, 1987.

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[23] Toxicological Data Sheet No. 21 INRS http: / / www.inrs.fr / publications / bdd / fichetox / fiche.html?refINRS=FICHETOX_21

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Claims

Claims

1. A method for detecting in a sample to be analyzed at least one amine-type compound, said compound being selected from hydrazine, ethanolamine and morpholine, using a reagent composition comprising a mixture of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid, said method comprising the steps of: a) mixing said sample to be analyzed with said reagent composition to obtain a mixture consisting of the sample to be analyzed and said reagent composition, b) detecting said amine-type compound(s) in the mixture consisting of the sample to be analyzed and said reagent composition.

2. The method of claim 1, wherein step b) further comprises quantifying said amine compound(s) in the mixture consisting of the sample to be analyzed and said reagent composition.

3. A method according to claim 1 or 2, wherein the sample to be analyzed is a liquid or gaseous sample or an aerosol.

4. Method according to one of claims 1 to 3, for which step b) of detection or detection and quantification is carried out by measuring the absorbance as a function of time of the mixture consisting of the sample to be analyzed and said composition of reagents.

5. Method according to one of claims 1 to 4, for which the ratio r of the concentrations of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid is from 1 to 20, preferably from 2 to 15, even more preferably 10.

6. A reagent composition comprising a mixture of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid.

7. Composition according to claim 6, for which the ratio r of the concentrations of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid is from 1 to 20, preferably from 2 to 15, even more preferably 10.

8. Use of a reagent composition according to claim 6 or 7 for the detection of at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine and morpholine.

9. Use of a reagent composition according to claim 6 or 7 for the quantification of at least one amine-type compound, said compound being selected from hydrazine, ethanolamine and morpholine.

10. A kit for preparing a reagent composition according to claim 6 or 7, said kit comprising: - a first container comprising 4-(dimethylamino)-cinnamaldehyde; - a second container comprising an aqueous solution of polystyrene sulfonic acid.

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