PROCESS FOR DETECTING AMINE-TYPE COMPOUNDS IN WATER AND AIR COMPARTMENTS

Abstract

A process for detecting at least one amine-type compound, the compound being chosen from hydrazine, ethanolamine, and morpholine, the process includes using a reagents composition including a mixture of 4-(dimethylamino)cinnamaldehyde and polystyrenesulfonic acid. Also, a kit for preparing the reagents composition, the reagents composition itself, and the uses of the reagents composition.

Claims

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

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

3. The process according to claim 1, wherein the sample to be analyzed is a liquid or gaseous sample or an aerosol.

4. The process according to claim 1, wherein the detection or detection and quantification step b) is performed by measuring the absorbance as a function of time of the mixture consisting of the sample to be analyzed and said reagents composition.

5. The process according to claim 1, wherein the ratio r of the concentrations of 4-(dimethylamino)cinnamaldehyde and polystyrenesulfonic acid is from 1 to 20.

6. A reagents composition comprising a mixture of 4-(dimethylamino)cinnamaldehyde and polystyrenesulfonic acid.

7. The composition according to claim 6, wherein the ratio r of the concentrations of 4-(dimethylamino)cinnamaldehyde and polystyrenesulfonic acid is from 1 to 20.

8. A method for detecting at least one amine-type compound, comprising mixing a sample with the reagents composition according to claim 6, said compound being chosen from hydrazine, ethanolamine, and morpholine.

9. A method for quantifying at least one amine-type compound, comprising mixing a sample with the reagents composition according claim 6, said compound being chosen from hydrazine, ethanolamine and morpholine.

10. A kit for preparing the reagents composition according to claim 6, said kit comprising: a first container comprising 4-(dimethylamino)cinnamaldehyde; and a second container comprising an aqueous solution of polystyrenesulfonic acid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Other features, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0049] FIG. 1 shows the scheme for the reaction between N.sub.2H.sub.4 and two molecules of DMACA, with the formation of a colored product 2DMACA-N.sub.2H.sub.4 absorbing in the visible range.

[0050] FIG. 2 shows the differential spectra obtained at different times, showing the evolution of the 2DMACA-N.sub.2H.sub.4 complex toward its protonated form, with the presence of an isobestic absorbance point at 553 nm. The conditions applied being as follows: DMACA 510.sup.3M+PSS 9.2 g.Math.L.sup.1+N.sub.2H.sub.4 5.510.sup.6M, quartz cell with 1 cm optical path length.

[0051] FIG. 3 shows the scheme for the reaction between NH.sub.2EtOH and DMACA, with formation of the NH.sub.2EtOH-DMACA complex absorbing at 474 nm.

[0052] FIG. 4 shows the differential spectra for the reaction between DMACA and NH.sub.2EtOH as a function of time. The conditions applied being as follows: DMACA 510.sup.3M+PSS 9.2 g.Math.L.sup.1+NH.sub.2EtOH 6.2410.sup.4M, quartz cell with 1 cm optical path length.

[0053] FIG. 5 shows the scheme for the reaction between morpholine and DMACA, with formation of the morpholine-DMACA complex.

[0054] FIG. 6 shows the spectral evolution of the morpholine-DMACA complex as a function of time. The conditions applied being as follows: DMACA 510.sup.3M+PSS 9.2 g.Math.L.sup.1+morpholine 6.2410.sup.4 M, quartz cell with 1 cm optical path length.

[0055] FIG. 7 shows the calibration lines for the variation in absorbance of the 2DMACA-N.sub.2H.sub.4 adduct as a function of [N.sub.2H.sub.4] concentration between 510.sup.7 and 5.510.sup.6 M. The conditions applied are as follows: at 553 nm (5 min, isobestic point), at 474 nm at 24 h and at 487 nm at 1 h, [DMACA]=510.sup.3 M, [PSS]=9.2 g.Math.L.sup.1, i.e. r=[H.sup.+]/[DMACA]=10, 1 cm optical path length.

[0056] FIG. 8 shows the calibration line for the variation in absorbance at 24 h of the DMACA-NH.sub.2EtOH adduct absorbing at 474 nm as a function of NH.sub.2EtOH concentration between 110.sup.4 and 210.sup.3 M, at 24 h. The following conditions are applied: 1 cm optical path length. [DMACA]=510.sup.3 M, [PSS]=9.2 g.Math.L.sup.1, i.e. r=[H.sup.+]/[DMACA]=10.

[0057] FIG. 9 shows the calibration line for the variation in absorbance at 1 h of the DMACA-morpholine adduct absorbing at 487 nm as a function of morpholine concentration between 510.sup.5 and 6.2410.sup.4 M at 1 h. The following conditions are applied: 1 cm optical path length. [DMACA]=510.sup.3 M, [PSS]=9.2 g.Math.L.sup.1, i.e. r=[H.sup.+]/[DMACA]=10.

[0058] FIG. 10 shows N.sub.2H.sub.4 measurements in the presence of interferents (NH.sub.3+NH.sub.2EtOH or NH.sub.3+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.

[0059] FIG. 11 shows a repeatability test for measurements of low N.sub.2H.sub.4 contents. The conditions applied being as follows: 60 min of sampling at a flow rate of 1 L.Math.min.sup.1 with sparging in 50 mL of a reagents solution (DMACA/PSS, r=10); with P=101325 Pa; R=8.3144621 J.Math.K.sup.1.Math.mol.sup.1; T=295 Kelvin.

DETAILED DESCRIPTION

[0060] The subject of the present invention is a process for detecting in a sample to be analyzed at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine, using a reagents composition comprising a mixture of 4-(dimethylamino)cinnamaldehyde and polystyrenesulfonic acid, said process comprising the steps of: [0061] a) mixing said sample to be analyzed with said reagents composition to obtain a mixture consisting of the sample to be analyzed and said reagents composition, [0062] b) detecting said amine-type compound(s) in the mixture consisting of the sample to be analyzed and said reagents composition.

[0063] In addition to detection, the process according to the invention may also allow determination in a sample to be analyzed of the concentration of at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine and morpholine. Thus, according to a particular embodiment, the present invention relates to a process for detecting and quantifying in a sample to be analyzed at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine and morpholine, using a reagents composition comprising a mixture of 4-(dimethylamino)cinnamaldehyde and polystyrenesulfonic acid, said process comprising the steps of: [0064] a) mixing said sample to be analyzed with said reagents composition to obtain a mixture consisting of the sample to be analyzed and said reagents composition, [0065] b) detecting and quantifying said amine-type compound(s) in the mixture consisting of the sample to be analyzed and said reagents composition.

[0066] Advantageously, the process according to the invention allows hydrazine detection, and also its quantification, despite the presence in the sample to be analyzed of interferents such as ammonia, ethanolamine or morpholine. The process according to the invention in this particular embodiment thus offers a real advantage, since it enables these amine-type compounds to be detected and quantified in a single step.

[0067] In the context of the present invention, the term quantification means determining the concentration of a compound within a sample to be analyzed.

[0068] The process according to the invention may advantageously be applied to a liquid or gaseous sample or an aerosol. The process according to the invention remains identical whether the sample to be analyzed is a liquid, a gas or an aerosol, only the method of collecting the sample to be analyzed may differ.

For the purposes of the present invention, the term liquid sample means a sample in the form of a solution or a suspension. For the purposes of the present invention, the term aerosol means a suspension, in air or in a gas, of solid or, more generally, liquid particles.

[0069] Step b) of detection or detection and quantification of the process according to the invention can be notably performed by measuring, as a function of time, the absorbance of the mixture consisting of the sample to be analyzed and said reagents composition. This step b) is thus performed in solution.

[0070] The advantages of the process according to the invention compared to those currently available, in particular that using the pDMAB reagent, are numerous: [0071] It allows hydrazine (N.sub.2H.sub.4) to be detected and optionally quantified selectively, in particular via measurement of the absorbance as a function of time of the 2DMACA-N.sub.2H.sub.4 adduct, whose absorption spectrum in the visible range extends between 460 and 620 nm. Such detection and quantification are possible and remain reliable despite the presence of high interferent concentrations compared to the hydrazine concentration in the sample. The interferent concentrations may thus be more than 200 times higher than the hydrazine concentration, without impairing the efficacy of the hydrazine detection process. [0072] In the case of a time-dependent absorbance measurement (also known as colorimetric measurement) of hydrazine in water, this is readily, rapidly and instantaneously achieved by collecting a specific volume of the solution to be analyzed and mixing it with the reagent solution. [0073] In the case of measurement by absorbance as a function of time, by virtue of the existence of a stable isobestic absorbance point in the absorption spectrum of the 2DMACA-N.sub.2H.sub.4 adduct, hydrazine measurement via the absorbance of the addition complex at this point may be instantaneous or performed after a delay of up to 3 days, as the inventors have demonstrated that the isobestic point is stable for at least 3 days. The experimenter can thus have an instantaneous measurement of the hydrazine concentration, for example at 5 min, and 3 days, for example to check it later if he so wishes. The isobestic point corresponds to a wavelength at which the absorbance is constant during a chemical reaction. Thus, in the present case, the chemical reaction involves a starting material (here, 2DMACA-N.sub.2H.sub.4) and an end product (protonated 2DMACA-N.sub.2H.sub.4), which have the same absorption coefficient at this wavelength. [0074] Measurement of hydrazine in air is performed using the same analytical method as when the sample is liquid, by collecting the air to be analyzed at constant speed and sparging it into the reagent solution for a specified period. Due to its high solubility, the N.sub.2H.sub.4 gas contained in the collected air is instantly dissolved in the reagent solution, and the N.sub.2H.sub.4 measurement is performed on the basis of the absorbance of the 2DMACA-N.sub.2H.sub.4 addition complex at the isobestic point. [0075] This allows measurement of the concentrations of the interferents, ethanolamine (NH.sub.2EtOH) or morpholine, in solution, notably by measuring the absorbance as a function of time of the adducts DMACA-NH.sub.2EtOH or DMACA-morpholine, whose absorption spectra differ from that of 2DMACA-N.sub.2H.sub.4. [0076] Quantification of ethanolamine or morpholine present in the air is also possible via their dissolution in the reagent solution and determination of the absorbance as a function of time of the colored DMACA-NH.sub.2EtOH or DMACA-morpholine complexes.

[0077] The analytical method which allows the determination of the contents of hydrazine and of interferents bearing a primary or secondary amine function by measuring absorbance as a function of time requires knowledge of the absorption spectra of the reagent solution, of the 2DMACA-N.sub.2H.sub.4 addition complexes and of the DMACA addition complexes with the interferents ethanolamine (NH.sub.2EtOH) and morpholine.

[0078] This method for measuring hydrazine in the presence of two interferents, NH.sub.2EtOH+NH.sub.3 or morpholine+NH.sub.3, advantageously comprises the sequence of steps detailed hereinbelow.

[0079] In aqueous solution, the reaction between hydrazine (N.sub.2H.sub.4) and 4-(dimethylamino)cinnamaldehyde (DMACA) catalyzed in the presence of polystyrenesulfonic acid gives rise to the formation of the red-colored 2DMACA-N.sub.2H.sub.4 addition complex ([FIG. 1] and [FIG. 2]).

[0080] The presence of polystyrenesulfonic acid is necessary to protonate DMACA and facilitate the addition of N.sub.2H.sub.4N.sub.2H.sub.4 to DMACA. However, N.sub.2H.sub.4 protonation may also take place in an acidic medium. This reaction would inhibit the formation of the 2DMACA-N.sub.2H.sub.4 addition complex. The amount of acid required for the reaction between N.sub.2H.sub.4 and DMACA must therefore be chosen to promote this reaction while at the same time minimizing N.sub.2H.sub.4 protonation.

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

[0082] This ratio is calculated from the molar concentrations of polystyrenesulfonic acid and 4-(dimethylamino)cinnamaldehyde (r=[H.sup.+]/[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.Math.L.sup.1 corresponds to a concentration of 0.05 mol.Math.L.sup.1 (=9.2/184). Thus, with a DMACA concentration of 5.Math.10.sup.3 mol.Math.L.sup.1 and a PSS concentration of 9.2 g.Math.L.sup.1 (0.05 mol.Math.L.sup.1), the ratio r is equal to 10.

[0083] Tests performed with different amounts of PSS acid, 1.84-3.68-5.98 and 9.2 g.Math.L.sup.1, i.e. with ratios r=[H.sup.+]/[DMACA] equal to 2-4-6.5 and 10, show, irrespective of the acidity of the medium, instantaneous formation of a product absorbing at 558 nm corresponding to the adduct, 2DMACA-N.sub.2H.sub.4. Moreover, there is an evolution of the product absorbing at 558 nm toward its protonated form absorbing at 535 nm, with the appearance of a stable isobestic point for 3 days. The wavelength corresponding to the isobestic point varies with the ratio r and thus ranges from 553 nm (r=10) to 538 nm (r=2).

[0084] 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.sup.+]/[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 510.sup.3 mol.Math.L.sup.1 corresponding to 0.876 g.Math.L.sup.1 (with M=175.23 g.Math.mol.sup.1) and a PSS concentration of 9.2 g.Math.L.sup.1, the ratio r is equal to 10.5.

[0085] DMACA also reacts with other amines such as NH.sub.2EtOH to give the NH.sub.2EtOH-DMACA complex absorbing at 474 nm ([FIG. 3] and [FIG. 4]).

[0086] FIG. 4 shows the formation of the NH.sub.2EtOH-DMACA complex and its evolution over time. The absorption maximum of the complex is at 474 nm, in a region where the 2DMACA-N.sub.2H.sub.4 complex and its protonated form practically do not absorb. The reaction between DMACA and NH.sub.2EtOH is much slower than that between DMACA and N.sub.2H.sub.4. For the determination of the NH.sub.2EtOH concentration, the time factor is taken into account for the calibration curve.

[0087] In the presence of morpholine, the morpholine-DMACA adduct is formed and absorbs at 487 nm (FIG. 5). The rate of formation of morpholine-DMACA is faster than that of ethanolamine-DMACA. Absorbance at 487 nm reaches a plateau after 1 h (FIG. 6).

[0088] According to a particular embodiment, the detection or detection and quantification process according to the invention can be performed according to the following steps: [0089] 1. Preparation of the reagents solution by mixing DMACA and PSS in water; [0090] 2. Establishment of N.sub.2H.sub.4 calibration curves from the absorbance of the 2DMACA-N.sub.2H.sub.4 addition complex at given wavelengths, for example at the isobestic point at 553 nm, at 487 nm (t=1 h) and at 474 nm (t=24 h); [0091] 3. Establishment of calibration curves for other amine-type compounds (interferents) at given wavelengths, for example 474 nm for ethanolamine and 487 nm for morpholine; [0092] 4. Preparation of the sample to be analyzed by mixing the reagents solution and the collected sample; [0093] 5. Measurement of the absorbance of the sample to be analyzed as a function of time (for example at 5 min, 1 h and 24 h); [0094] 6. Calculation of the concentrations of N.sub.2H.sub.4 and other amine-type compounds (interferents) from the spectra of absorbance as a function of time for the sample to be analyzed and the equations of the calibration curves previously obtained.

[0095] According to a particular embodiment, the process for detecting and quantifying N.sub.2H.sub.4 and NH.sub.2EtOH (or morpholine) in water according to the invention can be performed by means of the following steps:

1. Preparing the Reagents Solution by Mixing Defined Amounts of DMACA and PSS in water.

[0096] A reagent stock solution is thus obtained with known final concentrations of DMACA and PSS and a similarly defined ratio r of these concentrations=[H.sup.+]/[DMACA].

2. Establishing N.sub.2H.sub.4 Calibration Curves from the Absorbance of the 2DMACA-N.sub.2H.sub.4 Addition Complex at the Isobestic Point at 553 nm, at 487 nm (t=1 h) and at 474 nm (t=24 h).

[0097] N.sub.2H.sub.4 calibration curves are produced by adding a volume x (for example 5 mL) of solution containing varying concentrations of N.sub.2H.sub.4, in the range from 510.sup.7 to 5.510.sup.6 mol.Math.L.sup.1, to the same volume x of the reagents solution prepared in step 1. The solutions obtained are studied by UV-visible spectrophotometry between 5 min and 24 h using a quartz cell with a 1 cm optical path length.

[0098] Calibration curves are established at different wavelengths (FIG. 7): 553 nm (isobestic point), 474 nm (NH.sub.2EtOH absorption peak) at 24 h and 487 nm (morpholine absorption peak) at 1 h. Plotting the lines corresponding to the temporal evolution of absorbance as a function of N.sub.2H.sub.4 concentration will afford, by linear regression, the following equations:

At the isobestic point, Abs((2DMACA-N.sub.2H.sub.4) at 553 nm)=A[N.sub.2H.sub.4]

At 474 nm and 24h, Abs((2DMACA-N.sub.2H.sub.4) at 474 nm,24h)=A.sub.1[N.sub.2H.sub.4]

At 487 nm and at 1h, Abs((2DMACA-N.sub.2H.sub.4) at 487 nm,1h)=A.sub.2[N.sub.2H.sub.4].

3. Establishing the Calibration Curve for the NH.SUB.2.EtOH or Morpholine Interferent

3.a. Establishing the Calibration Curve for the NH.sub.2EtOH Interferent from Absorbance Measurements of the DMACA-NH.sub.2EtOH Complex at the Absorption Peak at 474 nm.

[0099] The NH.sub.2EtOH calibration curve is produced by adding a volume x (for example 5 mL) of solution containing varying concentrations of NH.sub.2EtOH, in the range 110.sup.4 to 210.sup.3 mol.Math.L.sup.1, to the same volume x of the reagents solution prepared in step 1.

[0100] The calibration curve of the DMACA-NH.sub.2EtOH adduct is produced by measuring the absorbance at 474 nm, at 24 h with a quartz cell of 1 cm optical path length. Plotting the line corresponding to the evolution of absorbance at 24 h as a function of NH.sub.2EtOH concentration will afford, by linear regression, the following equation:

Abs((DMACA-NH.sub.2EtOH) at 474 nm and 24h)=B[NH.sub.2EtOH](FIG. 8).

3.b. Establishment of the Calibration Curve for the Morpholine Interferent from the Absorbance Measurement of the DMACA-Morpholine Complex at the Absorption Peak at 487 nm.

[0101] The morpholine calibration curve is produced by adding a volume x (for example 5 mL) of solution containing varying concentrations of morpholine, in the range from 510.sup.5 to 6.2410.sup.4 mol.Math.L.sup.1, to the same volume x of the reagents solution prepared in step 1.

[0102] The calibration curve of the DMACA-morpholine adduct is produced by measuring the absorbance at 487 nm, at 1 h with a quartz cell of 1 cm optical path length. Plotting the line corresponding to the evolution of absorbance at 1 h as a function of morpholine concentration will afford, by linear regression, the following equation:

Abs((DMACA-morpholine) at 487 nm and 1h)=C[morpholine](FIG. 9).

4. Sampling

[0103] The collection of the sample to be analyzed, containing N.sub.2H.sub.4 and NH.sub.2EtOH (or N.sub.2H.sub.4 and morpholine), is performed as follows: [0104] In a volumetric flask, a volume x (for example 5 mL) of the reagents solution is introduced, followed by the same volume x of sample to be analyzed. The actual concentrations of the analytes having thus been diluted twofold in this mixture, whose absorbance will be measured, it is necessary to take account of this dilution by a coefficient 2 when calculating the concentrations. [0105] The absorption spectrum of the mixture composed of the reagents solution and the sample to be analyzed is collected between 400 and 700 nm at 5 min and at 24 h when the interferent is NH.sub.2EtOH. [0106] The absorption spectrum of the mixture composed of the reagents solution and the sample to be analyzed is collected between 400 and 700 nm at 5 min and at 1 h when the interferent is morpholine.

5. Calculations

5.a. Calculation of the N.sub.2H.sub.4 Concentration in the Mixture Containing N.sub.2H.sub.4 and NH2.sub.2EtOH (or Morpholine) is as Follows:

[0107] The absorbance (Abs) of the 2DMACA-N.sub.2H.sub.4 adduct is measured at the isobestic point of 2DMACA-N.sub.2H.sub.4 and protonated 2DMACA-N.sub.2H.sub.4, at 553 nm when r=10.

[0108] The N.sub.2H.sub.4 concentration of the sample in mol.Math.L.sup.1 is deduced using the calibration curve previously produced at the isobestic point Abs ((2DMACA-N.sub.2H.sub.4) at 553 nm)=A [N.sub.2H.sub.4], according to the equation:

[00001]$\left[N_2{H}_4\right]=\frac{\mathrm{Abs}\left(\left(2\mathrm{DMA}\mathrm{CA}-\mathrm{N2H4}\right)\mathrm{at}553\mathrm{nm}\right)}{A}2$

5.b. When the Interferent is NH.sub.2EtOH, the Calculation of the NH.sub.2EtOH Concentration in the Mixture Containing N.sub.2H.sub.4 and NH.sub.2EtOH is as Follows:

[0109] From the N.sub.2H.sub.4 concentration obtained in 5.a., the absorbance of 2DMACA-N.sub.2H.sub.4 at 474 nm and 24 h is obtained from the calibration curve Abs ((2DMACA-N.sub.2H.sub.4) at 474 nm, 24 h)=A1 [N.sub.2H.sub.4], obtained in 2.

[0110] The absorbance of DMACA-NHN.sub.2H.sub.4EtOH in the mixture at 24 h is deduced:

Abs((DMACA-NHN.sub.2H.sub.4EtOH) at 474 nm)=Abs((mixture) at 474 nm)Abs((2DMACA-N.sub.2H.sub.4) at 474 nm)

[0111] The NH.sub.2EtOH concentration in mol.Math.L.sup.1 of the sample is deduced from the calibration curve Abs (DMACA-NH.sub.2EtOH)=B [NH.sub.2EtOH] obtained in 3.a. (FIG. 8):

[00002]$\left[{\mathrm{NH}}_2\mathrm{Et}\mathrm{OH}\right]=2\frac{\mathrm{Abs}\left(\left(\mathrm{DMACA}-{\mathrm{NH}}_2\mathrm{Et}\mathrm{OH}\right)\mathrm{at}474\mathrm{nm}\right)}{B}$

5.c. When the Interferent is Morpholine, the Calculation of the Morpholine Concentration in the Mixture Containing N.sub.2H.sub.4 and Morpholine is as Follows:

[0112] From the N.sub.2H.sub.4 concentration obtained in 5.a., the absorbance of 2DMACA-N.sub.2H.sub.4 at 487 nm at 1 h is obtained from the calibration curve Abs ((2DMACA-N.sub.2H.sub.4) at 487 nm, 1 h)=A.sub.2 [N.sub.2H.sub.4], obtained in 2. (FIG. 7).

[0113] The absorbance of DMACA-morpholine in the mixture at 1 h is deduced:

Abs((DMACA-morpholine) at 487 nm)=Abs((mixture) at 487 nm)Abs((2DMACA-N.sub.2H.sub.4) at 487 nm,1h)

[0114] The morpholine concentration in mol.Math.L.sup.1 of the sample is deduced from the calibration curve Abs (DMACA-morpholine)=C [morpholine] obtained in 3.b. (FIG. 9):

[00003]$\left[\mathrm{morpholine}\right]=2\frac{\left(\mathrm{Abs}\right)\mathrm{at}487\mathrm{nm}}{C}$

[0115] According to another particular embodiment, when the sample to be analyzed is a gaseous sample, the steps of the process for detecting and quantifying N.sub.2H.sub.4 and NH.sub.2EtOH (or morpholine) according to the invention may be identical to those described above for a liquid sample to be analyzed. Nevertheless, the process for detecting and quantifying gaseous N.sub.2H.sub.4 and NH.sub.2EtOH (or morpholine) requires an additional step compared with the same process applied to a sample in aqueous solution. This additional step corresponds to collecting the ambient air to be analyzed and sparging it into the mixture of liquid reagents.

[0116] The sampling step may thus be performed as follows: the air to be analyzed is pumped at a known flow rate (e.g. 1 L.Math.min.sup.1) through a bubbler filled with a known volume (for example 50 mL) of the mixture of reagents DMACA and PSS. After one hour, the solution is collected for spectrophotometric analysis.

[0117] The spectrum of the mixture is then collected between 400 and 700 nm at 5 min and after 24 h when the interferent is NH.sub.2EtOH. The spectrum of the mixture is collected between 400 and 700 nm at 5 min and after 1 h when the interferent is morpholine.

[0118] A subsequent calculation step enables determination of the concentrations of N.sub.2H.sub.4 and NH.sub.2EtOH (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 stream of 1 L.Math.min.sup.1) for 1 hour must be taken into account.

5.a. Calculation of the Concentration of N.sub.2H.sub.4 in the Mixture Containing N.sub.2H.sub.4 and NH.sub.2EtOH (or Morpholine) is Calculated as Follows:

[0119] The absorbance (Abs) of the 2DMACA-N.sub.2H.sub.4 adduct is measured at the isobestic point of the 2DMACA-N.sub.2H.sub.4 and protonated 2DMACA-N.sub.2H.sub.4 complexes, at 553 nm when r=10.

[0120] The N.sub.2H.sub.4 concentration of the sample in mol.Math.L.sup.1 is deduced using the calibration curve previously produced at the isobestic point Abs ((2DMACA-N.sub.2H.sub.4) at 553 nm)=A [N.sub.2H.sub.4], according to the equation:

[00004]$\left[N_2{H}_4\right]=\frac{\mathrm{Abs}\left(\left(2\mathrm{DMA}\mathrm{CA}-\mathrm{N2H4}\right)\mathrm{at}553\mathrm{nm}\right)}{A}$

5.b. Calculation of the NH.sub.2EtOH Concentration in the Mixture Containing N.sub.2H.sub.4 and NH.sub.2EtOH is as Follows:

[0121] From the N.sub.2H.sub.4 concentration obtained in 5.a., the absorbance of 2DMACA-N.sub.2H.sub.4 at 474 nm and 24 h is obtained from the calibration curve Abs ((2DMACA-N.sub.2H.sub.4) at 474 nm, 1 h)=A.sub.1 [N.sub.2H.sub.4], obtained in 2.

[0122] The absorbance of DMACA-NH.sub.2EtOH in the mixture at 24 h is deduced from:

Abs((DMACA-NH.sub.2EtOH) at 474 nm)=Abs((mixture) at 474 nm)Abs((2DMACA-N.sub.2H.sub.4) at 474 nm)

[0123] The NH.sub.2EtOH concentration in mol.Math.L.sup.1 of the sample is deduced from the calibration curve Abs((DMACA-NH.sub.2EtOH) at 474 nm)=B [NH.sub.2EtOH] obtained in 3.a.:

[00005]$\left[{\mathrm{NH}}_2\mathrm{EtOH}\right]=\frac{\mathrm{Abs}\left(\mathrm{DMACA}-N{H}_2\mathrm{EtOH}\right)\mathrm{at}474\mathrm{nm}}{B}$

5.c. When the Interferent is Morpholine, the Calculation of the Morpholine Concentration in the Mixture Containing N.sub.2H.sub.4 and NH.sub.2EtOH is as Follows:

[0124] From the N.sub.2H.sub.4 concentration obtained in 5.a., the absorbance of 2DMACA-N.sub.2H.sub.4 at 487 nm at 1 h is obtained from the calibration curve Abs ((2DMACA-N.sub.2H.sub.4) at 487 nm)=A.sub.2 [N.sub.2H.sub.4], obtained in 2.

[0125] The absorbance of DMACA-morpholine in the mixture at 1 h is deduced:

Abs((DMACA-morpholine) at 487 nm)=Abs((mixture) at 487 nm)Abs((2DMACA-N.sub.2H.sub.4) at 487 nm)

[0126] The morpholine concentration in mol.Math.L.sup.1 of the sample, is deduced from the calibration curve Abs(DMACA-morpholine) at 487 nm)=C [morpholine] obtained in 3.b.

[00006]$\left[\mathrm{morpholine}\right]=\frac{\mathrm{Abs}\left(\mathrm{DMACA}-\mathrm{morpholine}\right)\mathrm{at}487\mathrm{nm})}{C}$

[0127] 5.d. The N.sub.2H.sub.4 (or NH.sub.2EtOH or Morpholine) Content in the Gas Mixture in Ppb is Deduced According to the Equation:

[00007]$\left[i\right]\left(\mathrm{ppb}\right)=\frac{\mathrm{number}\mathrm{of}\mathrm{moles}\mathrm{of}i}{\mathrm{number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{air}}*{10}^9$

with: [0128] i i=N.sub.2H.sub.4, NH.sub.2EtOH or morpholine [0129] number of moles of i=[i](mol.Math.L.sup.1)*V (V=volume of reagent solution=for example 5010.sup.3 L)

[00008]$\left[\mathrm{number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{air}\right]=\frac{D*}{V_m}$

(D=air flow rate=for example 1 L.Math.min.sup.1, t=sampling time=1 h, V.sub.m=air molar volume=24.21 L.Math.mol.sup.1 at 22 C.)

[0130] In addition to the detection method as defined previously, a subject of the present invention is also a reagents composition comprising a mixture of 4-(dimethylamino)cinnamaldehyde and polystyrenesulfonic acid. In a medium comprising an amine-type compound, for example hydrazine, ethanolamine or morpholine, this composition advantageously enables the reaction between the amine-type compound and 4-(dimethylamino)cinnamaldehyde, this reaction being catalyzed with polystyrenesulfonic acid and giving rise to the formation of an addition complex having absorbance properties in the UV-visible range.

[0131] The reaction between the amine-type compound 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 SO.sub.3H acid function for each styrene monomer. As a result, the number of available protons is particularly high, allowing the acidity of the solution to be adjusted to catalyze the reaction between DMACA and N.sub.2H.sub.4.

[0132] Moreover, inorganic acids and organic acids of low molecular weight have the drawback that acid vapors may be released during the step of sparging the gaseous mixture to be analyzed, the acid then being liable to evaporate off during the sparging. This drawback is not present for acids derived from a polymer, such as polystyrenesulfonic acid, as these acids are not volatile.

[0133] One of the major advantages of this reagents composition is its stability over time, which may be up to at least one week. This stability was demonstrated by the inventors by measuring the absorbance spectrum of the reagents composition up to one week after its preparation. The spectrum obtained was identical to that obtained directly after preparation of the composition. The composition may thus be prepared and stored for this length of time without impairing its efficacy in the process according to the invention. This feature advantageously removes the constraint of having to prepare the reagents composition prior to each sample analysis process.

[0134] 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 polystyrenesulfonic acid, this ratio ranging from 1 to 20, preferably from 2 to 15, even more preferentially 10.

[0135] A subject of the present invention is also the use of a reagents composition according to the invention for detecting at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine and morpholine.

[0136] According to a particular embodiment, the invention also relates to the use of a reagents composition according to the invention for the quantification of at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine and morpholine.

[0137] The use according to the invention may advantageously be applied on a liquid or gaseous sample or an aerosol.

[0138] Another subject of the present invention is a kit for preparing a reagents composition according to the invention, said kit comprising: [0139] a first container comprising 4-(dimethylamino)cinnamaldehyde; [0140] a second container comprising an aqueous solution of polystyrenesulfonic acid.
The kit according to the invention advantageously allows the reagents composition according to the invention to be prepared for its use in the process according to the invention. This preparation is particularly simple and quick to perform, since it only requires the mixing of two compounds in water.

EXAMPLES

Compounds Used

[0141] 4-(Dimethylamino)cinnamaldehyde (DMACA, Sigma-Aldrich, Ref: D4506-5 g, batch: BCBX0916, CAS: 6203-18-5, purity98%, molar mass=175.23 g/mol), [0142] Polystyrenesulfonic acid at 18% in water (PSS, Sigma-Aldrich, Ref: 561223-100 G, batch: MKBV7207V, CAS: 28210-41-5, molar mass75 000 g/mol, density=1.11 g/mL at 25 C.), [0143] Hydrazine hydrate at 50-60% in water (N.sub.2H.sub.4, Sigma-Aldrich, Ref: 225819-100 mL, batch: BCCC1556, CAS: 10217-52-4, molar mass=32.05 g/mol, density=1.029 g/mL at 25 C.), [0144] Ethanolamine (NH.sub.2EtOH, Sigma-Aldrich, Ref: 398136-500 mL, batch: STBJ4500, CAS: 141-43-5, purity98%, molar mass=61.08 g/mol, density=1.012 g/mL at 25 C.), [0145] Morpholine (Sigma-Aldrich, Ref: 252360-100 mL, batch: MCKM6935, CAS: 110-91-8, purity99%, molar mass=87.012 g/mol, density=0.996 g/mL at 25 C.), [0146] Aqueous 28% ammonia solution (NH.sub.3, VWR, Ref: 21182.94, batch: 15J260522, CAS: 1336-21-6, molar mass=17.03 g/mol, density d=0.89 g/mL), [0147] Milli-Q deionized water.

Example 1: Protocol for Assaying N.SUB.2.H.SUB.4 .and NH.SUB.2.EtOH (or Morpholine) in Aqueous Solutions with the Reagents Solution Containing [DMACA]=510.SUP.3 .M, [PSS]=9.2 g.Math.L.SUP.1., i.e. r=[H.SUP.+.]/[DMACA]=10

[0148] The assay of N.sub.2H.sub.4 and NH.sub.2EtOH (or morpholine) in water is performed as follows:

[0149] 1) Preparation of the reagents solution: 87.62 mg of DMACA and 4.604 mL of 18% PSS are placed in a 50 mL volumetric flask containing 25 mL of water. Water is added up to the graduation mark, and the solution is then sonicated in an ultrasonic bath for 30 minutes to fully dissolve the DMACA. A reagents stock solution is obtained with final DMACA and PSS concentrations of 0.01 M and 18.4 g.Math.L.sup.1, respectively. The ratio r=[H.sup.+]/[DMACA=10.

[0150] 2) Establishment of N.sub.2H.sub.4 calibration curves from the absorbance of the 2DMACA-N.sub.2H.sub.4 addition complex at the isobestic point at 553 nm, 487 nm (t=1 h) and 474 nm (t=24 h), for r=[H.sup.+]/[DMACA]=10) [0151] a) The N.sub.2H.sub.4 calibration curves are produced by adding 5 mL of solution containing varying concentrations of N.sub.2H.sub.4, in the range 510.sup.7 to 5.510.sup.6 mol.Math.L.sup.1, to 5 mL of reagents 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 (NH.sub.2EtOH absorption peak) at 24 h and 487 nm (morpholine absorption peak) at 1 h: [0152] At the isobestic point, Abs (553 nm)=Ax=29110 [N.sub.2H.sub.4]. [0153] At 474 nm and 24 h, Abs (474 nm, 24 h)=A.sub.1x=7080 [N.sub.2H.sub.4] [0154] At 487 nm and 1 h, Abs (487 nm, 1 h)=A.sub.2x=7810 [N.sub.2H.sub.4].

[0155] 3) Establishment of the calibration curve for NH.sub.2EtOH or morpholine interferent [0156] a) Establishment of the calibration curve for the NH.sub.2EtOH interferent from absorbance measurements of the DMACA-NH.sub.2EtOH complex at the absorption peak at 474 nm at 24 h.

[0157] The calibration curve for NH.sub.2EtOH is produced by adding 5 mL of solution containing varying concentrations of NH.sub.2EtOH, in the range 110.sup.4 to 210.sup.3 mol.Math.L.sup.1, to 5 mL of the reagents solution prepared in step 1). The calibration curve of the DMACA-NH.sub.2EtOH adduct is produced by measuring the absorbance at 474 nm, at 24 h with a quartz cell with a 1 cm optical path length.

[0158] Abs (DMACA-NH.sub.2EtOH) at 474 nm and 24 h=Bx=117 [NH.sub.2EtOH]([FIG. 8]). [0159] b) Calibration curve for the morpholine interferent based on absorbance measurements of the DMACA-morpholine complex at the absorption peak at 487 nm.

[0160] The morpholine calibration curve is produced by adding 5 mL of solution containing varying concentrations of morpholine, in the range from 510.sup.5 to 6.2410.sup.4 mol.Math.L.sup.1, to 5 mL of the reagents solution prepared in step 1). The calibration curve for the DMACA-morpholine adduct is produced by measuring the absorbance at 487 nm, at 1 h with a quartz cell with a 1 cm optical path length.

[0161] Abs (DMACA-morpholine) at 487 nm and 1 h=Cx=488 [morpholine](FIG. 9).

[0162] 4) Sampling

[0163] The solution to be analyzed, containing N.sub.2H.sub.4 and NH.sub.2EtOH (or N.sub.2H.sub.4 and morpholine), is collected as follows: [0164] 5 mL of the reagents solution are introduced into a 10 mL volumetric flask, followed by 5 mL of the sample to be analyzed. Since the actual concentrations of the analytes have been diluted twofold in the mixture, this dilution must be taken into account when calculating the concentrations. [0165] the absorption spectrum of the mixture is collected between 400 and 700 nm at 5 min and at 24 h when the interferent is NH.sub.2EtOH. [0166] 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.

[0167] 5) Calculations [0168] a) The concentration of N.sub.2H.sub.4 in the mixture containing N.sub.2H.sub.4 and NH.sub.2EtOH (or morpholine) is calculated as follows: [0169] Absorbance (Abs) of the 2DMACA-N.sub.2H.sub.4 adduct at the isobestic point, 553 nm. [0170] The N.sub.2H.sub.4 concentration of the sample in mol.Math.L.sup.1 is deduced using the calibration curve previously produced at the isobestic point Abs (553 nm)=Ax=29110 [N.sub.2H.sub.4], according to the equation:

[00009]$\left[N_2{H}_4\right]=\frac{\mathrm{Abs}\left(553\mathrm{nm}\right)}{29110}2$ [0171] b) When the interferent is NH.sub.2EtOH, the calculation of the NH.sub.2EtOH concentration in the mixture containing N.sub.2H.sub.4 and NH.sub.2EtOH is as follows: [0172] From the N.sub.2H.sub.4 concentration obtained in 5)a), the absorbance of 2DMACA-N.sub.2H.sub.4 at 474 nm and at 24 h is obtained from the calibration curve Abs (2DMACA-N.sub.2H.sub.4) at 474 nm, 24 h=7080 [N.sub.2H.sub.4], obtained in 2)a). [0173] The absorbance of DMACA-NH.sub.2EtOH in the mixture at 24 h is deduced:

Abs(DMACA-NH.sub.2EtOH) at 474 nm=Abs(mixture) at 474 nmAbs(2DMACA-N.sub.2H.sub.4) at 474 nm [0174] The NH.sub.2EtOH concentration in mol.Math.L.sup.1 of the sample is deduced from the calibration curve Abs(DMACA-NH.sub.2EtOH)=117 [NH.sub.2EtOH] obtained in 3)a) (FIG. 8):

[00010]$\left[N{H}_2\mathrm{EtOH}\right]=2\frac{\mathrm{Abs}\left(\mathrm{DMACA}-N{H}_2\mathrm{EtOH}\right)\mathrm{at}474\mathrm{nm}}{117}$ [0175] c) When the interferent is morpholine, the calculation of the morpholine concentration in the mixture containing N.sub.2H.sub.4 and morpholine is as follows: [0176] From the N.sub.2H.sub.4 concentration obtained in 5)a), the absorbance of 2DMACA-N.sub.2H.sub.4 at 487 nm at 1 h is obtained from the calibration curve Abs (2DMACA-N.sub.2H.sub.4) at 487 nm, 1 h=7810 [N.sub.2H.sub.4], obtained in 2)a) (FIG. 7). [0177] The absorbance of DMACA-morpholine in the mixture at 1 h is deduced:

Abs(DMACA-morpholine) at 487 nm=Abs(mixture) at 487 nmAbs(2DMACA-N.sub.2H.sub.4) at 487 nm [0178] The morpholine concentration in mol.Math.L.sup.1 of the sample, using the calibration curve Abs(DMACA-morpholine)=488 [morpholine] obtained in 3)b) (FIG. 9):

[00011]$\left[\mathrm{morpholine}\right]=2\frac{\left(\mathrm{Abs}\right)at487\mathrm{nm}}{488}$

Example 2: Protocol for Assaying N.SUB.2.H.SUB.4 .and NH.SUB.2.EtOH in Aqueous Solutions with the Reagents Solution Containing [DMACA]=510.SUP.3 .M, [PSS]=3.68 g.Math.L.SUP.1., i.e. r=[H.SUP.+.]/[DMACA]=4

[0179] The protocol is the same as described previously in Example 1 for the reagents solution containing DMACA and PSS, where r=[H.sup.+]/[DMACA]=10.

[0180] N.sub.2H.sub.4 calibration curves are established with a reagents solution containing [DMACA]=510.sup.3 M, [PSS]=3.68 g.Math.L.sup.1, where r=[H.sup.+]/[DMACA]=4, at different wavelengths: 542 nm (isobestic point) and 474 nm (absorption peak of NH.sub.2EtOH): [0181] At the isobestic point (at 542 nm), Abs (542 nm)=Ax=37744 [N.sub.2H.sub.4]. [0182] At 474 nm and 24 h, Abs (474 nm, 24 h)=A.sub.1x=9599 [N.sub.2H.sub.4].

[0183] The calibration curve for the DMACA-NH.sub.2EtOH adduct is established at 474 nm, at 24 h:

Abs (DMACA-NH.sub.2EtOH) at 474 nm and 24 h=Bx=429 [NH.sub.2EtOH]

Example 3: Protocol for Assaying N.SUB.2.H.SUB.4 .and NH.SUB.2.EtOH (or Morpholine) in the Gaseous State with the Reagents Solution Containing [DMACA]=510.SUP.3 .M, [PSS]=9.2 g.Math.L.SUP.1., i.e. r=[H.SUP.+.]/[DMACA]=10

[0184] For the measurement of gaseous analytes, gaseous N.sub.2H.sub.4 and NH.sub.2EtOH and morpholine must be generated and their concentrations calibrated.

[0185] The protocol for assaying gaseous N.sub.2H.sub.4 and NH.sub.2EtOH (or morpholine) requires an additional step compared with assaying these same analytes in aqueous solution. This step corresponds to collecting the ambient air to be analyzed and sparging it into the liquid reagent.

[0186] The protocol is the same as that described in Example 1 for the quantification of analytes in aqueous solution for steps 1), 2) 3).

[0187] Sampling step 4) is as follows: the air to be analyzed is pumped at a flow rate of 1 L.Math.min.sup.1 through a 3.16 cm diameter, 34 cm high bubbler filled with 50 mL of the reagents solution prepared in step 1). After one hour, the solution is collected for spectrophotometric analysis.

[0188] The spectrum of the mixture is collected between 400 and 700 nm at 5 min and after 24 h when the interferent is NH.sub.2EtOH.

[0189] The spectrum of the mixture is collected between 400 and 700 nm at 5 min and after 1 h when the interferent is morpholine.

[0190] Step 5) of the calculations enables determination of the concentrations of N.sub.2H.sub.4 and NH.sub.2EtOH (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 1 L.Math.min.sup.1 for 1 h must be taken into account. [0191] a) Calculation of the N.sub.2H.sub.4 concentration in the mixture containing N.sub.2H.sub.4 and NH.sub.2EtOH (or morpholine) is as follows: [0192] The absorbance (Abs) of the 2DMACA-N.sub.2H.sub.4 adduct at the isobestic point, 553 nm for r=[H.sup.+]/[DMACA]=10. [0193] The N.sub.2H.sub.4 concentration of the sample in mol.Math.L.sup.1 is deduced using the calibration curve previously produced at the isobestic point Abs (553 nm)=Ax=29110 [N.sub.2H.sub.4], according to the equation:

[00012]$\left[N_2{H}_4\right]=\frac{\mathrm{Abs}\left(553\mathrm{nm}\right)}{29110}$ [0194] b) Calculation of the NH.sub.2EtOH concentration in the mixture containing N.sub.2H.sub.4 and NH.sub.2EtOH is as follows: [0195] From the N.sub.2H.sub.4 concentration obtained in 5)a), the absorbance of 2DMACA-N.sub.2H.sub.4 at 474 nm and at 24 h is obtained from the calibration curve Abs (2DMACA-N.sub.2H.sub.4) at 474 nm, 1 h=7080 [N.sub.2H.sub.4], obtained in 2)a) (FIG. 9). [0196] The absorbance of DMACA-NH.sub.2EtOH in the mixture at 24 h is deduced from:

Abs(DMACA-NH.sub.2EtOH) at 474 nm=Abs(mixture) at 474 nmAbs((2DMACA-N.sub.2H.sub.4) at 474 nm [0197] The NH.sub.2EtOH concentration in mol.Math.L.sup.1 of the sample is deduced from the calibration curve Abs(DMACA-NH.sub.2EtOH)=117 [NH.sub.2EtOH] obtained in 3)a):

[00013]$\left[N{H}_2\mathrm{EtOH}\right]=\frac{\mathrm{Abs}\left(\mathrm{DMACA}-N{H}_2\mathrm{EtOH}\right)\mathrm{at}474\mathrm{nm}}{117}$ [0198] c) When the interferent is morpholine, calculation of the morpholine concentration in the mixture containing N.sub.2H.sub.4 and NH.sub.2EtOH is as follows: [0199] From the N.sub.2H.sub.4 concentration obtained in 5)a), the absorbance of 2DMACA-N.sub.2H.sub.4 at 487 nm at 1 h is obtained from the calibration curve Abs (2DMACA-N.sub.2H.sub.4) at 487 nm, 1 h=7810 [N.sub.2H.sub.4], obtained in 2)a) (FIG. 9). [0200] The absorbance of DMACA-morpholine in the mixture at 1 h is deduced:

Abs(DMACA-morpholine) at 487 nm=Abs(mixture) at 487 nmAbs((2DMACA-N.sub.2H.sub.4) at 487 nm [0201] The morpholine concentration in mol.Math.L.sup.1 of the sample, using the calibration curve Abs(DMACA-morpholine)=488 [morpholine] obtained in 3)b) (FIG. 11):

[00014]$\left[\mathrm{morpholine}\right]=\frac{\left(\mathrm{Abs}\right)\mathrm{at}487\mathrm{nm}}{488}$ [0202] d) The N.sub.2H.sub.4 (or NH.sub.2EtOH or morpholine) content in the gas mixture in ppb is deduced according to the equation:

[00015]$\left[i\right]\left(\mathrm{ppb}\right)=\frac{n\mathrm{umber}\mathrm{of}\mathrm{moles}\mathrm{of}i}{n\mathrm{umber}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{air}}*{10}^9$ [0203] with: [0204] i=N.sub.2H.sub.4, NH.sub.2EtOH, or morpholine [0205] number of moles of i=[i](mol.Math.L.sup.1)*V (V=volume of reagent solution=5010.sup.3 L)

[00016]$\left[\mathrm{number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{air}\right]=\frac{D*}{V_m}$

(D=air flow rate=1 L.Math.min.sup.1, t=sampling time=1 h, V.sub.m=molar volume=24.21 L.Math.mol.sup.1 at 22 C.)

Example 4: Application of the Process According to the Invention to the Determination of N.SUB.2.H.SUB.4 .and NH.SUB.2.EtOH in Aqueous Solutions Containing Different Analyte Concentrations and in the Presence of a Strong Base, NH.SUB.3 .with 50 [N.SUB.2.H.SUB.4.]<[NH.SUB.3.]<100 [N.SUB.2.H.SUB.4.]. Reagents Solution: [DMACA]=510.SUP.3 .M, [PSS]=9.2 g.Math.L.SUP.1., i.e. r=[H.SUP.+.]/[DMACA]=10 and the Isobestic Point at 553 nm

[0206] Seven examples of application of the method are given here. Mixtures of known concentrations of N.sub.2H.sub.4, NH.sub.2EtOH and NH.sub.3 with different ratios of [NH.sub.3]/[N.sub.2H.sub.4] and [NH.sub.2EtOH]/[N.sub.2H.sub.4] were prepared and the spectra of the mixtures were collected at 24 h. These spectra were analyzed by collecting absorbance values at the specific wavelengths, 553 and 474 nm, to deduce the concentrations of N.sub.2H.sub.4 and NH.sub.2EtOH. The calculated values were then compared with the theoretical concentration values (Table 1).

TABLE-US-00001 TABLE 1 [N.sub.2H.sub.4] 10.sup.6M Calcul- [NH.sub.2EtOH] 10.sup.4M ation Calcula- Devia- [00017]$\frac{\left[{\mathrm{NH}}_3\right]}{\left[N_2{H}_4\right]}$ [00018]$\frac{\left[{\mathrm{NH}}_2\mathrm{Et}\mathrm{OH}\right]}{\left[N_2{H}_4\right]}$ [NH.sub.3] 10.sup.4M Theoretical ( = 7%) Theo- retical Devia- tion (%) tion ( = 7%) Theo- retical tion (%) 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: Assay results for N.sub.2H.sub.4 and NH.sub.2EtOH in the mixture containing NH.sub.3, N.sub.2H.sub.4 and NH.sub.2EtOH. [DMACA] = 5 10.sup.3M, [PSS] = 9.2 g.L.sup.1, i.e. r = [H.sup.+]/[DMACA] = 10, 1 cm optical path length. Deviation = (calculated value theoretical value)/theoretical value.

[0207] This example demonstrates the very good reliability of the process according to the invention, in particular as regards the detection and quantification of hydrazine, since very small deviations (less than 6%) are observed between the calculated and theoretical values.

[0208] This example also demonstrates the very good sensitivity of the process as regards the detection and quantification of hydrazine, since the concentrations calculated via the process are very close to the theoretical concentrations despite concentrations of interferents (NH.sub.3 or NH.sub.2EtOH) up to 100 times greater than that of hydrazine.

Example 5: Application of the Process According to the Invention to the Determination of N.SUB.2.H.SUB.4 .and Morpholine in Aqueous Solutions Containing Different Analyte Concentrations and in the Presence of a Strong Base, NH.SUB.3 .with [NH.SUB.3.]=150 [N.SUB.2.H.SUB.4.]. Reagents Solution: [DMACA]=510.SUP.3 .M, [PSS]=9.2 g.Math.L.SUP.1., i.e. r=[H.SUP.+.]/[DMACA]=10 and the Isobestic Point at 553 nm

[0209] Four examples of application of the analytical method are given here. Mixtures of known concentrations of N.sub.2H.sub.4, morpholine and NH.sub.3 with ratios of [NH.sub.3]/[N.sub.2H.sub.4]=100 and [morpholine]/[N.sub.2H.sub.4]=100 were prepared and the spectra of the mixtures were collected at 1 h. These spectra were analyzed by collecting absorbance values at specific wavelengths, 553 and 487 nm, to deduce the N.sub.2H.sub.4 and morpholine concentrations. The calculated values are then compared with theoretical concentration values (Table 2).

TABLE-US-00002 TABLE 2 Assay results for N.sub.2H.sub.4 and morpholine in the mixture containing NH.sub.3, N.sub.2H.sub.4 and morpholine. [NH.sub.3] = [morpholine] = 100 [N.sub.2H.sub.4], [DMACA] = 5 10.sup.3M, [PSS] = 9.2 g .Math. L.sup.1, 1 cm optical path length. Deviation = (calculated value theoretical value)/theoretical value. [NH.sub.3] (10.sup.4M) [N.sub.2H.sub.4] (10.sup.6M) [morpholine] (10.sup.4M) 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

[0210] As with Example 1, this example demonstrates the very good reliability of the process according to the invention, in particular as regards the detection and quantification of hydrazine, since very small deviations (less than 7%) are observed between the calculated and theoretical values.

[0211] This example also demonstrates the very good sensitivity of the process as regards the detection and quantification of hydrazine, since the concentrations calculated via the process are very close to the theoretical concentrations despite concentrations of interferents (NH.sub.3 and morpholine) 100 times greater than that of hydrazine.

Example 6: Application of the Process According to the Invention to the Determination of N.SUB.2.H.SUB.4 .and NH.SUB.2.EtOH in Aqueous Solutions Containing Different Analyte Concentrations and in the Presence of a Strong Base, NH.SUB.3 .with [NH.SUB.3.][NH.SUB.2.EtOH]=96.55 [N.SUB.2.H.SUB.4.]. Reagents Solution: [DMACA]=510.SUP.3 .M, [PSS]=3.68 g.Math.L.SUP.1., i.e. r=[H.SUP.+.]/[DMACA]=4 and the Isobestic Point at 542 nm

[0212] Four examples of application of the analytical method are given here. Mixtures of known concentrations of N.sub.2H.sub.4, NH.sub.2EtOH and NH.sub.3 with ratios of [NH.sub.3]/[N.sub.2H.sub.4]=96.55 and [NH.sub.2EtOH]/[N.sub.2H.sub.4]=96.55 were prepared and the spectra of the mixtures were collected at 24 h. These spectra were analyzed by collecting absorbance values at the specific wavelengths, 542 nm and 474 nm, to deduce the concentrations of N.sub.2H.sub.4 and NH.sub.2EtOH. The calculated values were then compared with theoretical concentration values (Table 3).

TABLE-US-00003 TABLE 3 Blind assay results for NH.sub.2EtOH and N.sub.2H.sub.4 with r = 4 in the mixture containing NH.sub.3, N.sub.2H.sub.4 and NH.sub.2EtOH. [NH.sub.3] = [NH.sub.2EtOH] = 96.55 [N.sub.2H.sub.4], [DMACA] = 5 10.sup.3M, [PSS] = 3.68 g .Math. L.sup.1, i.e. r = [H.sup.+]/[DMACA] = 4, quartz cell with 1 cm optical path length. Deviation = ((calculated value theoretical value)/theoretical value). [NH.sub.3] [N.sub.2H.sub.4] (10.sup.6M) [NH.sub.2EtOH] (10.sup.4M) (10.sup.4M) Calculation Deviation Calculation (24 h) Deviation Theoretical ( = 7%) Theoretical (%) ( = 7%) Theoretical (%) 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

[0213] As for Examples 1 and 2, this example demonstrates the very good reliability of the process according to the invention, in particular as regards the detection and quantification of hydrazine, since very small deviations (less than 4%) are observed between the calculated and theoretical values.

[0214] This example also demonstrates the very good sensitivity of the process as regards the detection and quantification of hydrazine, since the concentrations calculated by means of the process are very close to the theoretical concentrations despite interferent concentrations (NH.sub.3 and NH.sub.2EtOH) almost 100 times greater than that of hydrazine.

Example 7: Aqueous Solution Measurements of N.SUB.2.H.SUB.4 .in the Presence of Interferents on Industrial Sites

[0215] Liquid hydrazine measurements were taken on four samples collected on an industrial site. In addition to hydrazine, the samples also contained other amines such as NH.sub.2EtOH+NH.sub.3 or morpholine+NH.sub.3 in varying concentrations. The results of the measurements taken were systematically compared with the automated amperometric measurements produced on the sampled lines, and with the measurements taken with the pDMAB (p-dimethylaminobenzaldehyde) reagent. FIG. 10 shows the set of results obtained.

[0216] This example shows that the process according to the invention afforded hydrazine concentration results very close to those obtained via the known method using pDMAB. Specifically, concentration differences of less than 2 g/L are observed between the two methods.

Example 5: Application of the Process According to the Invention to the Determination of Gaseous N.SUB.2.H.SUB.4 .and NH.SUB.2.EtOH in Ambient Air Containing Different Analyte Concentrations and in the Presence of a Strong Base, NH.SUB.3 .with 85 [N.SUB.2.H.SUB.4.]<[NH.SUB.3.]<116 [N.SUB.2.H.SUB.4.]. Reagents Solution: [DMACA]=510.SUP.3 .M, [PSS]=9.2 g.Math.L.SUP.1., i.e. r=[H.SUP.+.]/[DMACA]=10

[0217] Five examples of application of the method are given here. Mixtures of known concentrations of N.sub.2H.sub.4, NH.sub.2EtOH and NH.sub.3 with different ratios of [NH.sub.3]/[N.sub.2H.sub.4] and [NH.sub.2EtOH]/[N.sub.2H.sub.4] were prepared. The air to be analyzed was pumped at a flow rate of 1 L.Math.min.sup.1 and bubbled through 50 mL of reagent for 1 h. The spectra of the mixtures were collected at 24 h. These spectra were analyzed by collecting the absorbance values at the specific wavelengths, 553 and 474 nm, to deduce the concentrations of N.sub.2H.sub.4 and NH.sub.2EtOH. The calculated values were then compared with the theoretical concentration values (Table 4).

TABLE-US-00004 TABLE 4 [N.sub.2H.sub.4] ppb [NH.sub.2EtOH] ppm [00019]$\frac{\left[{\mathrm{NH}}_3\right]}{\left[N_2{H}_4\right]}$ [00020]$\frac{\left[{\mathrm{NH}}_2\mathrm{Et}\mathrm{OH}\right]}{\left[N_2{H}_4\right]}$ [NH.sub.3] ppm Theoretical Calculation ( = 7%) Theoretical ( = 8%) Devi- ation (%) Calculation (24 h) ( = 7%) Theo- retical Devia- tion (%) Ex. 1 99 1 10.6 9.6 10.8% 0.95 Ex. 2 111 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% Assay results for gaseous N.sub.2H.sub.4 and NH.sub.2EtOH in the mixture containing NH.sub.3, N.sub.2H.sub.4 and NH.sub.2EtOH, with 50 mL of reagent containing [DMACA] = 5 10.sup.3M, [PSS] = 9.2 g.L.sup.1, i.e. r = [H.sup.+]/[DMACA] = 10, quartz cell with 1 cm optical path length. T = 22 C. Deviation = (calculated value theoretical value)/theoretical value.

[0218] This example demonstrates the very good reliability of the process according to the invention applied to a gaseous sample, in particular as regards the detection and quantification of hydrazine, since small deviations (less than 18%) are observed between the calculated and theoretical values.

[0219] This example also demonstrates the very good sensitivity of the process of the invention applied to a gaseous sample as regards the detection and quantification of hydrazine, since the concentrations calculated by means of the process are very close to the theoretical concentrations despite proportions of interferents (NH.sub.3 or NH.sub.2EtOH) up to 100 times greater than that of hydrazine.

Example 6: Application of the Process According to the Invention to the Determination of N.SUB.2.H.SUB.4 .in Ambient Air Containing Different Concentrations of Gaseous Morpholine Analytes and in the Presence of a Strong Base, NH.SUB.3 .with 57 [N.SUB.2.H.SUB.4.]<[NH.SUB.3.]<164 [N.SUB.2.H.SUB.4.]. Reagents Solution: [DMACA]=510.SUP.3 .M, [PSS]=9.2 g.Math.L.SUP.1., i.e. r=[H.SUP.+.]/[DMACA]=10

[0220] Seven examples of application of the method are given here. Mixtures of known concentrations of N.sub.2H.sub.4, morpholine and NH.sub.3 with different ratios of [NH.sub.3]/[N.sub.2H.sub.4] and [morpholine]/[N.sub.2H.sub.4] were prepared on an experimental gas bench. The air to be analyzed was pumped at a flow rate of 1 L.Math.min.sup.1 and bubbled 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 the specific wavelengths, 553 and 487 nm, to deduce the concentrations of N.sub.2H.sub.4 and morpholine. The calculated values are then compared with theoretical concentration values (Table 5).

TABLE-US-00005 TABLE 5 [N.sub.2H.sub.4] ppb [morpholine] ppm [NH.sub.3] [N.sub.2H.sub.4] [00021]$\frac{\left[\mathrm{morpholine}\right]}{\left[N_2{H}_4\right]}$ [NH.sub.3] ppm Theoretical Calculation ( = 7%) Theoretical ( = 8%) Devia- tion (%) Calculation (1 h) ( = 7%) Theo- retical Devia- tion (%) 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% Ex. 6 99 103 5 52.8 50.5 4.6% 4.6 5.2 11.5% Ex. 7 57 46 1.6 32.8 28.3 15.9% 1.1 1.3 15.4% Results of N.sub.2H.sub.4 assay in the mixture containing NH.sub.3, N.sub.2H.sub.4 and morpholine, with 50 mL of reagents containing [DMACA] = 5 10.sup.3M, [PSS] = 9.2 g.L.sup.1, i.e. r = [H.sup.+]/[DMACA] = 10, quartz cell with 1 cm optical path length. T = 22 C. Deviation = (calculated value theoretical value)/theoretical value.

[0221] As for Example 5, this example demonstrates the very good reliability of the process according to the invention applied to a gaseous sample, in particular as regards the detection and quantification of hydrazine, since small deviations (less than 16%) are observed between the calculated and theoretical values.

[0222] This example also demonstrates the very good sensitivity of the process according to the invention applied to a gaseous sample as regards the detection and quantification of hydrazine, since the concentrations calculated by means of the process are very close to the theoretical concentrations despite proportions of interferents (NH.sub.3 or morpholine) up to 170 times greater than that of hydrazine.

Example 9: Examples of Gaseous N.SUB.2.H.SUB.4 .Measurements at Two Concentration Levels

[0223] Air samples were taken from the gaseous 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 at 1% by weight.

[0224] 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, as the hydrazine concentration in this sample is not known.

[0225] The duration of sampling and sparging in the reagents solution (DMACA/PSS with r=10) is 1 hour.

TABLE-US-00006 [N.sub.2H.sub.4].sub.air Standard [N.sub.2H.sub.4].sub.air Standard (g/m.sup.3) deviation (ppb) deviation Tank 1 89 13 67 10 Tank 2 70 8 53 6

[0226] This experiment demonstrates the good reproducibility of the hydrazine quantification process in a gaseous sample, since the standard deviations reported in the above table are low.

[0227] With the object of evaluating the reproducibility of the method on samples of lower concentration, 20 samples were taken at a distance of 7 meters from the abovementioned tank 1, which was covered with a non-leaktight lid. These samples were taken under identical experimental conditions. Hydrazine concentrations of 1.80 ppb were measured. FIG. 11 shows the distribution of the results obtained for all the samples produced.

[0228] This experiment demonstrates the very good repeatability of the process according to the invention applied to a gaseous sample with a low hydrazine concentration since, with the exception of one measurement, all the results show measurement variations of less than 0.5 ppb, which is really minimal.

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