Derivatization gas chromatography method for measuring water content in unsaturated halogenated hydrocarbon

Abstract

The invention provides a method for detecting the water content in unsaturated halogenated hydrocarbon. The method comprises the following steps: fully reacting the water content in to-be-detected unsaturated halogenated hydrocarbon with excessive derivatization reagents; adding excessive alcohol to react with the unreacted derivatization reagent to generate a separable derivatization product, and testing the content of the derivatization product by adopting a chromatographic internal standard method so as to calculate the amount of the derivatization reagent which reacts with water; and calculating the water content of the unsaturated halogenated hydrocarbon according to the derivatization reagent reacting with water, wherein the derivatization reagent comprises at least one derivatization reagent selected from the following groups: phthalic anhydride, acetic anhydride and trifluoroacetic anhydride.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of analytical testing technology, in particular to a method for determining the water content in unsaturated halogenated hydrocarbons by derivatization gas chromatography, which has the characteristics of high sensitivity, rapidness and strong universality. The method is suitable for water content detection of unsaturated halogenated hydrocarbon raw materials and process materials and quality inspection of finished products. BACKGROUND

[0002] As low ozone depletion potential (ODP) and low global warming potential (GWP) working medium, solvent and monomer, unsaturated halogenated hydrocarbons are mainly used in refrigeration, air conditioning and heat pump working conditions. They have high matching degree with existing refrigeration systems, excellent heat transfer performance and cycle efficiency, and can realize high system energy efficiency ratio. In terms of engineering adaptation, they have good thermal stability and chemical stability, good compatibility with common equipment metal materials and lubricating oil systems; in terms of safety, they can be configured as a low-flammable grade system, have low toxicity and narrow combustion limit, and can improve the overall safety level by blending, suitable for residential and commercial air conditioning, data center cooling and low-temperature cold chain and other scenarios. With the continuous improvement of energy efficiency standards, the demand for environmentally friendly, low leakage risk and high energy efficiency working medium is increasing, and the engineering value of unsaturated halogenated hydrocarbon working medium in green substitution and system energy saving is increasingly prominent.

[0003] In terms of safety compliance, environmental impact and reliable operation of equipment, the quality control indicators of unsaturated halogenated hydrocarbon working medium include trace water and acidity, main component purity and isomer composition, volatile / semi-volatile organic impurities, stabilizer / inhibitor content, and trace metals and particulate matter. Among them, water content is a key parameter affecting system reliability and service life, and excessive water content can easily cause corrosion and side reactions, reduce electrical insulation, and may form ice blockage at the throttling part, directly affecting incoming material inspection, process deviation analysis and yield accounting. Existing industrial practice often refers to GB / T 6283-2008 Determination of Moisture Content in Chemical Products Karl Fischer Method to carry out moisture determination: the sample is introduced into the titration cell, the end point is determined by potential jump, and the water content is calculated according to the consumption of titrant. For halogenated olefin matrix, in order to reduce interference, the balance solvent needs to be refreshed between samples and the pool liquid and electrode need to be maintained, which results in limited throughput and fluctuating parallelism. However, Karl Fischer reagent has inherent limitations in this type of matrix: the iodine in the titrant will add to the double bond, which directly leads to the additional consumption of effective iodine; and the reducing impurities or stabilizers in the production process will also compete for the consumption of titrant; as a result, the pool liquid water content, environmental humidity and operating conditions are highly sensitive, which is not conducive to automation and batch processing.

[0004] Therefore, there is an urgent need in the field to develop an improved method for detecting water content in unsaturated haloalkanes. This method avoids side reaction interference, has high sensitivity, a simple process, strong matrix resistance, and is compatible with existing gas chromatographs. It also has significant advantages in terms of accuracy, repeatability, throughput, and method transferability. Summary of the Invention

[0005] The first aspect of the present invention provides a method for detecting the water content in unsaturated haloalkanes, the method comprising the following steps: (1) React the water in the unsaturated haloalkanes to be tested with an excess of derivatizing reagent until fully reacted; (2) Add excess alcohol and react with unreacted derivatizing reagent to generate separable derivatized products. Use the internal standard method of chromatography to test the content of derivatized products, and then calculate the amount of derivatizing reagent that reacts with water. (3) Calculate the water content of the unsaturated halohydrocarbon based on the amount of derivatizing reagent reacting with water, wherein the derivatizing reagent includes at least one derivatizing reagent selected from the group consisting of phthalic anhydride, acetic anhydride, trifluoroacetic anhydride, preferably acetic anhydride.

[0006] A second aspect of the invention provides the use of chromatographic internal standard method in detecting the water content in unsaturated haloalkanes, wherein the water in the unsaturated haloalkanes to be tested reacts fully with an excess of derivatizing reagent; an excess of alcohol is added to react with the unreacted derivatizing reagent to generate a separable derivatized product; the content of the derivatized product is tested using chromatographic internal standard method, thereby calculating the amount of derivatizing reagent reacting with water; the water content of the unsaturated haloalkanes is calculated based on the amount of derivatizing reagent reacting with water, wherein the derivatizing reagent includes at least one derivatizing reagent selected from the group consisting of phthalic anhydride, acetic anhydride, and trifluoroacetic anhydride.

[0007] A third aspect of the invention provides the use of a derivatizing reagent in the determination of water content in unsaturated haloalkanes using an internal standard chromatographic method, wherein the derivatizing reagent is at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and trifluoroacetic anhydride. Attached Figure Description

[0008] Figure 1 According to one embodiment of the present invention, a derivatization gas chromatogram of a blank mixture comprising a derivatizing reagent and an alcohol is provided. Figure 2 According to one embodiment of the present invention, a derivatization gas chromatogram of a reaction mixture comprising the unsaturated haloalkanes to be tested, a derivatizing reagent, and an alcohol is provided. Detailed Implementation

[0009] This invention addresses the problems of systematic bias, insufficient selectivity and reproducibility, and limited operational sensitivity and throughput in the existing Karl Fischer method for unsaturated haloalkanes due to the involvement of iodine in the reaction. It provides an indirect quantitative analysis method based on derivatization gas chromatography, enabling accurate determination of water content in unsaturated haloalkanes. This method avoids interference from the addition of iodine to olefin double bonds and redox side reactions, achieving high sensitivity, high accuracy, and strong repeatability. It can serve as an engineered alternative for the quality control of unsaturated haloalkanes, facilitating routine laboratory testing and on-site production, and supporting batch sample testing for incoming material inspection, process monitoring, and finished product quality control.

[0010] Unless otherwise specified in this specification, the components or their preferred components may be combined to form new technical solutions.

[0011] Unless otherwise specified in this specification, all the embodiments and preferred embodiments mentioned can be combined to form new technical solutions.

[0012] Unless otherwise specified in this specification, all the technical features and preferred features mentioned can be combined to form new technical solutions.

[0013] Unless otherwise specified, the term "a" as used in this specification means "at least one".

[0014] Unless otherwise specified, all percentages, parts, etc. in this specification refer to weight.

[0015] The "range" disclosed herein takes the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges that can be defined in this way are inclusive and composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0016] Unless otherwise specified in this specification, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0017] In this specification, unless otherwise specified, the terms "comprising" and "including" as used herein can be open-ended or closed-ended. For example, "comprising" and "including" may mean that other components not listed may also be included, or that only the listed components may be included.

[0018] This application provides a method for detecting the water content in unsaturated haloalkanes, the method comprising the following steps: (1) React the water in the unsaturated haloalkanes to be tested with an excess of derivatizing reagent until fully reacted; (2) Add excess alcohol and react with unreacted derivatizing reagent to generate separable derivatized products. Use the internal standard method of chromatography to test the content of derivatized products, and then calculate the amount of derivatizing reagent that reacts with water. (3) Calculate the water content of the unsaturated halohydrocarbon based on the derivatizing reagent that reacts with water, wherein the derivatizing reagent includes at least one derivatizing reagent selected from the group consisting of phthalic anhydride, acetic anhydride, and trifluoroacetic anhydride.

[0019] In this application, "unsaturated haloalkanes" refers to olefins or alkynes substituted with one or more halogen atoms, wherein the halogen atoms are selected from fluorine, chlorine, bromine, and iodine atoms. In one specific embodiment of the invention, the unsaturated haloalkanes are unsaturated haloalkanes, preferably unsaturated haloalkanes having 2-5 carbon atoms. The unsaturated haloalkanes include, but are not limited to, tetrafluorobutene, dichloroethylene, tetrafluoropropylene, tetrachloropropylene, and dichloropropylene. In one specific embodiment of the invention, the unsaturated haloalkanes include at least one olefin selected from the group consisting of tetrafluoropropylene, tetrachloropropylene, and dichloropropylene.

[0020] In this application, the derivatizing reagent is an acid anhydride compound, which can react with water in unsaturated haloalkanes and simultaneously undergo derivatization reactions with alcohols under relatively mild conditions to generate ester derivatized products. By reacting water in the unsaturated haloalkanes with excess acid anhydride compound, and then using an alcohol to convert the remaining acid anhydride compound into an ester, the generated ester can be quantitatively detected by a gas chromatograph equipped with a flame ionization detector (GC-FID). The amount of acid anhydride compound that did not react with water can be calculated, thereby estimating the water content in the unsaturated haloalkanes, ultimately achieving indirect, selective, and accurate quantification of water. The derivatizing reagent includes, but is not limited to, phthalic anhydride, acetic anhydride, and trifluoroacetic anhydride. The alcohols include, but are not limited to, methanol, ethanol, and propanol.

[0021] In one specific embodiment of the present invention, the derivatizing agent comprises at least one derivatizing agent selected from the group consisting of phthalic anhydride, acetic anhydride, and trifluoroacetic anhydride. In a preferred specific embodiment of the present invention, the derivatizing agent is acetic anhydride. In one specific embodiment of the present invention, the alcohol comprises at least one alcohol selected from the group consisting of methanol, ethanol, and propanol. In a preferred specific embodiment of the present invention, the alcohol is ethanol.

[0022] In this invention, the chromatographic method includes, but is not limited to, gas chromatography and liquid chromatography. Preferably, the chromatographic method is gas chromatography. More specifically, this invention uses a gas chromatograph equipped with a flame ionization detector (GC-FID) for detection. A derivatizing reagent (e.g., acetic anhydride) is used to quantify the water content, followed by quenching the remaining derivatizing reagent with an alcohol (e.g., ethanol) to generate a separable derivatized product. GC separation and detection are then used to indirectly determine the water content. The core metrological relationship is as follows: by quantifying the chromatographic peak of the derivatized product (e.g., ethyl acetate) using GC-FID, the amount of derivatizing reagent involved in the quenching reaction is calculated, i.e., the amount of "remaining derivatizing reagent"; combined with the difference in the amount of initially added derivatizing reagent, the amount and mass fraction of water in the sample are calculated. This method avoids interference from the addition of iodine to olefin double bonds and redox side reactions; FID has a high and stable response to oxygen-containing organic compounds, a wide linear range, and can be corrected using either external or internal standards, facilitating automated injection and batch processing, and enabling highly sensitive quantification.

[0023] In the method of this invention, there is no particular limitation on the amount of derivatizing reagent used, as long as it is in excess relative to the water content in the sample to be tested. The ratio of alcohol to derivatizing reagent is 2.5:1 to 4:1, by weight.

[0024] In this invention, the content of the derivatized product is detected through the following steps: (1) Construct a stock standard solution for the internal standard correction factor of the derivatized products, and calculate the correction factor of the derivatized products using the internal standard method. f ; (2) Construct a blank mixture of derivatizing reagent and alcohol and carry out derivatization reaction. Test the content of derivatization product in the blank mixture by internal standard method; (3) Construct a reaction mixture of the unsaturated haloalkanes to be tested, the derivatizing reagent and the alcohol and carry out the derivatization reaction. The content of the derivatized products in the reaction mixture is tested by the internal standard method.

[0025] Constructing a stock solution of internal standard correction factors for derivatized products involves mixing the derivatized product and an internal standard, wherein the purity of both the derivatized product and the internal standard is >99.5%. There are no particular restrictions on the selection of the internal standard, as long as the chromatographic peak position of the internal standard differs significantly from that of the derivatized product, allowing for the calculation of the content of the derivatized product in the mixture using the internal standard method. Internal standards that can be used in the method of this invention include, but are not limited to, monochlorobenzene, n-butanol, and m-dichlorobenzene. In one specific embodiment of this invention, the internal standard includes at least one compound selected from the group consisting of monochlorobenzene, n-butanol, and m-dichlorobenzene. In a preferred embodiment of this invention, the internal standard is monochlorobenzene.

[0026] The correction factor of the derivatized product is calculated using the following formula (1). f : (1) In the formula: m1 represents the mass of the derivatized product in the internal standard correction factor stock solution; A1 represents the peak area value of the derivatized product in the internal standard correction factor stock solution; m2 is the mass of the internal standard in the internal standard solution of the internal standard method correction factor; A2 represents the peak area value of the internal standard in the internal standard stock solution for the internal standard method correction factor.

[0027] Constructing a blank mixture of derivatizing reagent and alcohol involves mixing the derivatizing reagent and alcohol, testing the content of the derivatizing reagent in a blank system without the analyte sample using an internal standard method, then constructing a reaction mixture of the analyte unsaturated haloalkane, the derivatizing reagent, and the alcohol, and performing a derivatization reaction. The content of the derivatized product in the reaction mixture is then tested using an internal standard method. Since the derivatized product and the internal standard may have different polarities and may be immiscible, a solvent may be optionally added during the preparation of the internal standard correction factor stock solution, the blank mixture, and the reaction mixture to make the derivatized product and the internal standard miscible. The solvent includes, but is not limited to, acetonitrile, DMF, etc. There is no particular limitation on the amount of solvent added, as long as it allows the derivatized product and the internal standard to be miscible. In one embodiment of the invention, the solvent is acetonitrile.

[0028] In one embodiment of the present invention, the stock standard solution comprises 1-5 wt% of the derivatized product, 1-5 wt% of the internal standard, and the balance being solvent, based on the total weight of the stock standard solution. In one embodiment of the present invention, the blank mixture comprises 1-5 wt% of the derivatized product, 2-10 wt% of the alcohol, 1-5 wt% of the internal standard, and the balance being solvent, based on the total weight of the blank mixture. In one embodiment of the present invention, the reaction mixture containing the unsaturated haloalkane to be tested comprises 0.5-3 wt% of the unsaturated haloalkane to be tested, 0.7-5 wt% of the derivatizing reagent, 1-10 wt% of the alcohol, 1-5 wt% of the internal standard, and the balance being solvent, based on the total weight of the reaction mixture containing the unsaturated haloalkane to be tested.

[0029] The derivatization reaction can be carried out under relatively mild conditions, with a reaction temperature of 20-50°C, preferably 30-40°C, and a reaction time of 10-60 minutes, preferably 20-30 minutes. There are no particular restrictions on the timing of the addition of the internal standard; it can be added after the derivatization reaction is complete, or it can be added simultaneously with the derivatization reagent and the alcohol. After the derivatization reaction has proceeded sufficiently and completely, the content of the derivatized product in the mixture is tested using chromatographic internal standard method.

[0030] The content of the derivatized product in the mixture is calculated using the following formula (2): (2) In the formula: m3 is the mass of the mixture added during the test; A3 represents the peak area of ​​the derivatized product in the mixture; m4 is the mass of the internal standard added during the test; A4 represents the peak area of ​​the internal standard in the mixture; and f The correction factor for the stock standard solution used as the internal standard method correction factor.

[0031] The content of derivatized products in the blank mixture can be calculated using the above formula (2). 1, where m3 is the mass of the blank mixture; A3 is the peak area of ​​the derivatized product in the blank mixture; m4 is the mass of the added internal standard; and A4 is the peak area of ​​the internal standard in the blank mixture.

[0032] The content of derivatized products in the reaction mixture can also be calculated using the above formula (2). 2, where m3 is the mass of the reaction mixture; A3 is the peak area of ​​the derivatized product in the reaction mixture; m4 is the mass of the added internal standard; and A4 is the peak area of ​​the internal standard in the reaction mixture.

[0033] Then, based on the content of derivatized products in the blank mixture... 1. Content of derivatized products in the reaction mixture 2. Calculate the water content of the unsaturated halohydrocarbon. The water content of the unsaturated halohydrocarbon can be calculated using the following formula (3): X (%) = (M0 - (m + m0) 2 / (88.11) 100)) 18 100 / m (3) In the formula, M0 is the number of moles of derivatizing reagent in the blank mixture that can react with alcohol, expressed as M0 = m0. 1 / (88.11 100) Perform the calculation, where m0 is the total mass of derivatizing reagent and alcohol added when constructing the blank mixture. 1 represents the content of derivatized products in the blank mixture; 2 represents the content of the derivatized product in the reaction mixture; m represents the mass of the unsaturated halohydrocarbon to be tested.

[0034] Another aspect of this application provides the use of chromatographic internal standard method in detecting the water content in unsaturated haloalkanes, wherein the water in the unsaturated haloalkanes to be tested reacts fully with an excess of derivatizing reagent; an excess of alcohol is added to react with the unreacted derivatizing reagent to generate a separable derivatized product; the content of the derivatized product is tested using chromatographic internal standard method, thereby calculating the amount of derivatizing reagent reacting with water; the water content of the unsaturated haloalkanes is calculated based on the amount of derivatizing reagent reacting with water, wherein the derivatizing reagent includes at least one derivatizing reagent selected from the group consisting of phthalic anhydride, acetic anhydride, and trifluoroacetic anhydride.

[0035] Another aspect of this application provides the use of a derivatizing reagent in the determination of water content in unsaturated haloalkanes by chromatographic internal standard method, wherein the derivatizing reagent is at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and trifluoroacetic anhydride.

[0036] Example

[0037] The present invention will now be described in further detail with reference to embodiments. However, it should be understood that these embodiments are provided for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless specific conditions are specified, are generally determined according to national standards. If no corresponding national standard exists, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed. Unless otherwise stated, all parts are parts by weight, and all percentages are weight percentages.

[0038] Raw material sources and preparation

[0039] Main reagents for the experiment

[0040] The GC-FID gas chromatography conditions are as follows: Column: Agilent DB-5 (30m) 320 0.25µm); FID detector temperature: 300℃; vaporization chamber temperature: 280℃; constant flow rate: 1.3mL / min; combustion gas (hydrogen) flow rate: 30mL / min; combustion gas (air) flow rate: 400mL / min; compensation gas (nitrogen) flow rate: 25mL / min; split ratio: 30:1; injection volume: 0.4µL.

[0041] Table 1 Temperature program for gas chromatography

[0042] Example 1: Weigh 0.15 g (accurate to 0.0001 g) of ethyl acetate and 0.20 g of the internal standard monochlorobenzene into a centrifuge tube, and dilute to 10 mL with acetonitrile. Prepare stock standard solution 1 for the ethyl acetate internal standard method correction factor. Analyze stock standard solution 1 using GC-FID, record the peak areas of ethyl acetate and monochlorobenzene, and calculate the correction factor according to the following formula. f。

[0043]

[0044] In the formula: m1 is the mass of ethyl acetate added to the stock standard solution, in grams; A1 represents the peak area of ​​ethyl acetate in the stock standard solution; m2 is the mass of monochlorobenzene added to the stock standard solution, in grams; A2 represents the peak area of ​​monochlorobenzene in the stock standard solution; Weigh 0.20 g (accurate to 0.0001 g) of ethyl acetate and 0.20 g of the internal standard monochlorobenzene into a centrifuge tube, and dilute to 10 mL with acetonitrile. Prepare stock standard solution 2 for the ethyl acetate internal standard method correction factor. Analyze stock standard solution 2 using GC-FID, and record the peak areas of ethyl acetate and monochlorobenzene. f Calculation formula for calculating correction factor f 2 ； Weigh 0.25 g (accurate to 0.0001 g) of ethyl acetate and 0.20 g of the internal standard monochlorobenzene into a centrifuge tube, and dilute to 10 mL with acetonitrile. Prepare the ethyl acetate internal standard method correction factor stock solution 3. Analyze the stock solution 3 using GC-FID, and record the peak areas of ethyl acetate and monochlorobenzene. f Calculation formula for calculating correction factor f 3 ； Pick f 1 、f2 、f 3 The average value is obtained. f。

[0045] The peak areas of ethyl acetate and chlorobenzene for each stock standard solution and the calculated correction factors are listed in Table 1 below.

[0046] Table 1

[0047] Accurately transfer 0.5 mL of acetic anhydride and 1.0 mL of anhydrous ethanol into a centrifuge tube using a pipette and weigh them, recording the weight as m0. Sonicate at 40°C for 30 min.

[0048] Weigh 0.20 g of the above mixture, denoted as m3 (m3 = 0.20 g), and add 0.20 g of monochlorobenzene, denoted as m4 (m4 = 0.20 g). Place the mixture in a dry centrifuge tube, bring the volume to 10 mL with acetonitrile, shake well, filter, and perform gas chromatography analysis. Obtain the derivatized gas chromatogram of the blank mixture, as shown below. Figure 1 As shown, the characteristic peak area of ​​ethyl acetate in the mixture is A3, and the characteristic peak area of ​​the internal standard monochlorobenzene is A4. According to... Calculation formula for calculating the content of ethyl acetate in blank mixture 1:

[0049] In the formula: m3 represents the mass of the added mixture, in grams. A3 represents the peak area of ​​ethyl acetate; m4 represents the mass of monochlorobenzene added, in grams; A4 represents the peak area of ​​monochlorobenzene; f This is the correction factor for the stock standard solution.

[0050] Then, calculate the number of moles of acetic anhydride (M0) that can react with ethanol in the blank system according to the following formula, as shown in Table 2: M0 = m0 1 / (88.11 100); In the formula, m0 is the mass of the blank mixture, that is, the total mass of the added derivatization reagent and ethanol, in g; 1 represents the content of ethyl acetate in the blank mixture.

[0051] Table 2

[0052] Weigh 0.50 g of standard 1 (accurate to 0.0001 g) into a dry centrifuge tube, denoted as m (m = 0.50 g). Accurately pipette 0.5 mL of acetic anhydride and 1.0 mL of anhydrous ethanol and weigh them, denoted as m0 (m0 = 1.3281 g). Sonicate at 40℃ for 30 min. Weigh 0.20 g of the reaction solution, denoted as m3 (m3 = 0.20 g), and 0.20 g of monochlorobenzene, denoted as m4 (m4 = 0.20 g), into a dry centrifuge tube. Dilute with acetonitrile to 8 mL, shake well, filter, and perform gas chromatography analysis. Obtain the derivatized gas chromatogram of the reaction mixture after the standard derivatization reaction, as shown below. Figure 2 Raw material sources and preparation As shown, the characteristic peak area of ​​ethyl acetate is A3, and the characteristic peak area of ​​the internal standard chlorobenzene is A4. The formula is used to calculate the content of ethyl acetate in the reaction mixture. 2. Substitute the calculated data into the moisture content calculation formula to calculate the sample moisture content X, as shown in Table 3: X (%) = (M0 - (m + m0) 2 / (88.11 100)) 18 100 / m.

[0053] Table 3

[0054] Repeated sampling and repeated experiments were conducted, and the water content measurements obtained are shown in Table 4.

[0055] Weigh out 0.50g of standard sample 2 and test the water content using the same steps as above. The results are also listed in Table 4.

[0056] Table 4. Moisture content test results

[0057] The relative errors of the test results were all <3%, and the RSD was <2%, indicating that the water content detection method of the present invention has high accuracy.

[0058] Example 2: The same steps and conditions as in Example 1 were used, except that the temperature of the derivatization reaction was changed. The derivatization reaction was carried out by sonication at 30°C for 30 minutes.

[0059] Example 3: The same steps and conditions as in Example 1 were used, except that the derivatization time was changed and the derivatization reaction was carried out by sonication at 40°C for 10 minutes.

[0060] The detection results of Examples 2 and 3 are shown in Table 5: Table 5. Moisture content test results

[0061] Table 5 shows the effect of derivatization reaction conditions on the degree of reaction completion. Under the reaction conditions of 30°C, more than 90% of the reaction was completed in 30 minutes, and under the reaction conditions of 40°C, more than 95% of the reaction was completed in 10 minutes. Therefore, the preferred derivatization reaction conditions of this invention are 100% completion of the derivatization reaction within 30 minutes at 40°C.

[0062] Example 4

[0063] The same steps and conditions as in Example 1 were used, except that phthalic anhydride was used as the derivatization reagent. Standard 1 was analyzed using the derivatization gas chromatography method of the present invention, and the results are as follows: Table 6. Water content test results using phthalic anhydride as a derivatization reagent

[0064] As shown in Table 6, phthalic anhydride, when used as a derivatizing reagent to detect the water content of unsaturated haloalkanes, exhibits a higher relative error and RSD than acetic anhydride. The accuracy and repeatability of water content detection are significantly reduced. This is because the derivatization reaction of acetic anhydride with ethanol is more complete than that of phthalic anhydride, and phthalic anhydride is a solid at room temperature while acetic anhydride is a liquid, making acetic anhydride easier to handle. Therefore, acetic anhydride is the preferred derivatizing reagent in this invention.

[0065] Comparative Example 1: Determination of water content in unsaturated haloalkanes using the Karl Fischer volumetric method

[0066] Add approximately 50 mL of anhydrous methanol to the titration vessel and perform a pre-titration to the endpoint. Accurately weigh 0.02 g of ultrapure water and add it to the titration vessel for calibration. After the system reequilibrates, accurately weigh 0.10 g of standard 1 and quickly add it to the titration vessel. After titration, record the volume of reagent consumed using a Karl Fischer moisture analyzer and calculate the water content. The results are shown in the table below: Table 7. Results of water content determination using the Karl Fischer method

[0067] As shown in Table 7, the method for detecting the water content of unsaturated haloalkanes provided in this application has a smaller error when detecting standards compared with the commonly used titration method in the prior art. For the detection of water content in unsaturated haloalkanes, chromatography is significantly superior to titration.

Claims

1. A method for detecting the water content in unsaturated haloalkanes, the method comprising the following steps: (1) React the water in the unsaturated haloalkanes to be tested with an excess of derivatizing reagent until fully reacted; (2) Add excess alcohol and react with unreacted derivatizing reagent to generate separable derivatized products. Use the internal standard method of chromatography to test the content of derivatized products, and then calculate the amount of derivatizing reagent that reacts with water. (3) Calculate the water content of the unsaturated halohydrocarbon based on the amount of derivatizing reagent reacting with water, wherein the derivatizing reagent includes at least one derivatizing reagent selected from the group consisting of phthalic anhydride, acetic anhydride, trifluoroacetic anhydride, preferably acetic anhydride.

2. The method of claim 1, wherein the chromatographic internal standard method for determining the content of the derivatized product includes: (1) Construct a stock standard solution for the internal standard correction factor of the derivatized products, and calculate the correction factor of the derivatized products using the internal standard method. f ; (2) Construct a blank mixture of derivatizing reagent and alcohol and carry out derivatization reaction. Test the content of derivatization product in the blank mixture by internal standard method; and (3) Construct a reaction mixture of the unsaturated haloalkanes to be tested, the derivatizing reagent and the alcohol and carry out the derivatization reaction. The content of the derivatized products in the reaction mixture is tested by the internal standard method.

3. The method as described in claim 1 or 2, wherein the correction factor of the derivatized product f The calculation is performed using the following formula (1): （1） In the formula: m1 represents the mass of the derivatized product in the internal standard correction factor stock solution; A1 represents the peak area value of the derivatized product in the internal standard correction factor stock solution; m2 is the mass of the internal standard in the internal standard solution of the internal standard method correction factor; A2 represents the peak area value of the internal standard in the internal standard stock solution for the internal standard method correction factor.

4. The method of claim 1 or 2, wherein the content of the derivatized product is calculated using the following formula (2): （2） In the formula: m3 is the mass of the added mixture; A3 represents the peak area of ​​the derivatized product in the mixture; m4 represents the mass of the added internal standard. A4 represents the peak area of ​​the internal standard in the mixture; and f The correction factor for the stock standard solution used as the internal standard method correction factor.

5. The method of claim 2, wherein the water content of the unsaturated halohydrocarbon is calculated by the following formula (3): X(%)= (M0-(m+m0) 2 / (88.11 100)) 18 100 / m (3) In the formula: M0 is the number of moles of derivatizing reagent in the blank mixture that can react with alcohol, expressed as M0 = m0. 1 / (88.11 100) is used for calculation, where 1 represents the content of derivatized products in the blank mixture; m0 is the total mass of the added derivatizing reagent and alcohol; 2 represents the content of derivatized products in the reaction mixture; m represents the mass of the unsaturated halohydrocarbon to be tested.

6. The method according to claim 1 or 2, wherein the derivatization reaction is carried out at a temperature of 20-50°C and for a reaction time of 10-60 minutes.

7. The method of claim 1 or 2, wherein the amount of alcohol relative to the derivatizing agent is 2.5:1 to 4:1, by weight.

8. The method of claim 1 or 2, wherein the unsaturated haloalkane is an unsaturated haloalkene.

9. The application of the chromatographic internal standard method in the determination of water content in unsaturated haloalkanes, wherein the water in the unsaturated haloalkanes to be tested reacts fully with an excess of derivatizing reagent; an excess of alcohol is added to react with the unreacted derivatizing reagent to generate a separable derivatized product; the content of the derivatized product is tested using the chromatographic internal standard method, thereby calculating the amount of derivatizing reagent reacting with water; the water content of the unsaturated haloalkanes is calculated based on the amount of derivatizing reagent reacting with water, wherein the derivatizing reagent includes at least one derivatizing reagent selected from the group consisting of phthalic anhydride, acetic anhydride, and trifluoroacetic anhydride.

10. Use of a derivatizing reagent in the determination of water content in unsaturated haloalkanes by chromatographic internal standard method, wherein the derivatizing reagent is at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and trifluoroacetic anhydride.

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