A method for analyzing the purity of heptafluoropropane extinguishing agent

Abstract

The application discloses a method for analyzing the purity of heptafluoropropane extinguishing agent, which comprises the following steps: (1) configuring heptafluoropropane and impurity standard gas; (2) selecting a chromatographic column type; (3) setting gas chromatograph analysis conditions; and (4) detecting a sample to be measured. Compared with the prior art, the method has the advantages of simple operation, better separation effect and higher accuracy.

Description

Technical Field

[0001] This invention relates to analytical methods for organofluorine compounds, specifically to a method for analyzing the purity of heptafluoropropane fire extinguishing agent. Background Technology

[0002] HFC-227ea, also known as 1,1,1-2-3,3,3-heptafluoropropane, has the molecular formula C3HF7 and a molecular weight of 170.04. It is classified as a Class 2.2 non-flammable gas. At room temperature and pressure, HFC-227ea is a colorless, almost odorless, and non-conductive gas, with a density approximately six times that of air. Under its own pressure, it is a colorless and transparent liquid, non-toxic and non-corrosive, exhibiting good thermal and chemical stability. HFC-227ea has a boiling point of -16.4℃ and a liquid density (at 21℃) of 1403 kg / m³. 3 Freezing point: -131.1℃, ozone depletion potential (ODP) is zero, global warming potential (GWP) is 3220.

[0003] HFC-227ea is a clean gas extinguishing agent. Due to its high extinguishing efficiency, low toxicity, non-destructive effect on the atmospheric ozone layer, and no pollution to the application site, it is considered an ideal alternative to Halon 1301. It has been included in the NFPA 2001 fire extinguishing product standard by the National Fire Protection Association of the United States and is currently widely used in key protection areas such as various computer rooms, power distribution rooms, substations, archives, containers, and industrial equipment.

[0004] The national standard for HFC-227ea fire extinguishing agent (GB 18614-2012) officially came into effect on October 1, 2013. The standard stipulates that the purity of heptafluoropropane fire extinguishing agent should be determined by gas chromatography. However, in the actual testing process, analysts found the following defects in the chromatographic conditions for purity determination:

[0005] (1) The detector temperature range of 30 to 300℃ is too wide. Generally, hydrogen flame detectors are difficult to ignite below 150℃.

[0006] (2) The chromatographic column used was a GASPRO 30m×0.32mm capillary column with a flow rate of 20mL / min and a split ratio of 40:1. Generally, the recommended flow rate for capillary columns of this diameter is 1 to 5mL / min. A flow rate of 20mL / min is too high, and the column simply cannot handle it. Moreover, with a split ratio of 40:1, the split flow rate is very high, and the chromatographic conditions cannot be met.

[0007] (3) The compensation gas flow rate is 45 mL / min. If the flow rate is too high, it will easily blow out the detector flame. The generally recommended compensation gas flow rate is 20 to 30 mL / min.

[0008] (4) The standard recommends a column oven temperature of 200℃. Using such a high temperature in a 30m long column results in a very fast peak elution time, poor separation of impurity peaks, and unreliable measurement results.

[0009] (5) The standard does not provide typical chromatograms, the peak conditions are unclear, and impurities cannot be identified.

[0010] (6) The standard does not specify the injection volume, nor does it specify whether it is manual injection or valve injection.

[0011] In summary, the current method for determining purity is not very practical, and there is an urgent need to develop a simple, effective, and accurate method for analyzing the purity of HFC-227ea. Summary of the Invention

[0012] The purpose of this invention is to address the shortcomings of existing methods by providing a simple, effective, and accurate method for analyzing the purity of heptafluoropropane fire extinguishing agents.

[0013] To achieve the above objectives, the technical solution adopted by this invention is: a method for analyzing the purity of heptafluoropropane fire extinguishing agent, comprising the following steps:

[0014] (1) Prepare standard gas of heptafluoropropane and impurities

[0015] Heptafluoropropane and impurity standard gases were prepared by extracting different gas volumes of HFC-227ea, 1,1,3,3,3-pentafluoro-1-propene, hexafluoropropene, 1,2,3,3,3-pentafluoro-1-propene, octafluoro-n-butene (trans), octafluoro-n-butene (cis), 1,1,1,2,4,4,4-heptafluoro-2-butene, and 1,1,1,3,3,3-hexafluoropropane according to their percentage content.

[0016] (2) Select the type of chromatographic column;

[0017] (3) Set the gas chromatograph analysis conditions;

[0018] (4) Detect the sample to be tested;

[0019] Using the column type in step (2) and the analytical conditions in step (3), after the gas chromatograph reaches the set state, the purity of the heptafluoropropane and impurity standard gas prepared in step (1) is analyzed.

[0020] In a preferred embodiment of the present invention, the mass percentage of HFC-227ea in the heptafluoropropane and impurity standard gas is 97-99%.

[0021] In a preferred embodiment of the present invention, the chromatographic column type is one of the following: GASPRO 30m×0.32mm capillary column, GASPRO 60m×0.32mm capillary column, or DB-5MS 30m×0.25mm quartz capillary column.

[0022] In a preferred embodiment of the present invention, the detector of the gas chromatograph is a flame hydrogen detector.

[0023] In a preferred embodiment of the present invention, the gas chromatograph analysis conditions are as follows:

[0024] (1) Inlet temperature: 180~250℃;

[0025] (2) Detection chamber temperature: 180~280℃;

[0026] (3) Column flow rate: 2-10 mL / min;

[0027] (4) Column oven temperature: programmed temperature rise;

[0028] (5) Compensating gas flow rate: 20-30 mL / min;

[0029] (6) Injection mode: split injection, split ratio is 40:1.

[0030] In a preferred embodiment of the present invention, the injection volume is 0.05 to 0.6 mL.

[0031] In a preferred embodiment of the present invention, the programmed temperature rise refers to: maintaining the temperature at 60-120°C for 6-10 minutes, then raising it to 140-200°C at a rate of 5-10°C / min and maintaining it for 6 minutes.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. Simple to operate: This invention optimizes and verifies the national standard method, especially improving the chromatographic column type and gas chromatograph operating conditions, determining the linear range of the injection volume, significantly optimizing the operation steps and parameters, and making it highly operable.

[0034] 2. The separation effect is good and the accuracy is high. The purity analysis method of heptafluoropropane fire extinguishing agent of the present invention has high separation degree, beautiful peak shape, appropriate analysis time, good repeatability, small standard deviation, linear correlation coefficient of main content is 0.9909, impurity recovery rate is between 96.7% and 103.7%, and standard deviation is between 0.00034 and 0.00052. This method can meet the needs of heptafluoropropane fire extinguishing agent detection. Attached Figure Description

[0035] Figure 1The spectrum is the experimental result of Example 1 of the present invention;

[0036] Figure 2 The spectrum is the experimental result of Example 2 of the present invention;

[0037] Figure 3 The spectrum is the experimental result of Example 3 of the present invention;

[0038] Figure 4 The spectrum is the experimental result of Example 4 of the present invention;

[0039] Figure 5 The spectrum is the experimental result of Comparative Example 1 of this invention;

[0040] Figure 6 This is a standard curve of the injection volume and peak area of ​​the present invention. Detailed Implementation

[0041] The present invention will be further described clearly and completely below with reference to embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0042] Example 1

[0043] 1. Prepare standard gas containing heptafluoropropane and impurities.

[0044] Standard gases were prepared by extracting different gas volumes of HFC-227ea, 1,1,3,3,3-pentafluoro-1-propene, hexafluoropropene, 1,2,3,3,3-pentafluoro-1-propene, octafluoro-n-butene (trans), octafluoro-n-butene (cis), 1,1,1,2,4,4,4-heptafluoro-2-butene, and 1,1,1,3,3,3-hexafluoropropane according to their percentage content. The resulting standard gases were prepared using 2500 mL gas mixing bottles to obtain heptafluoropropane and impurity standard gases. The content and composition are shown in Table 1.

[0045] Table 1. Standard gases containing heptafluoropropane and impurities prepared in Example 1

[0046]

[0047] 2. Select the column type

[0048] Instrument: 7890 gas chromatograph, Agilent Technologies, equipped with a flame ionization detector, manual injection; Column type: GASPRO 30m × 0.32mm capillary column.

[0049] 3. Set the operating conditions for the gas chromatograph

[0050] The experiment was conducted under the following chromatographic conditions with a standard gas injection volume of 0.2 mL:

[0051] Inlet temperature: 180℃;

[0052] Detector temperature: 180℃;

[0053] Column flow rate: 2 mL / min;

[0054] Injection mode: Split injection;

[0055] Flow split ratio: 40:1;

[0056] Compensating gas flow rate: 20 L / min;

[0057] Temperature program: Hold at 60℃ for 6 minutes, then increase to 140℃ at a rate of 5℃ / min and hold for 6 minutes.

[0058] 4. Detect the sample to be tested.

[0059] Following the column type and chromatographic conditions specified in steps 2 and 3, after the instrument reaches the set state, inject the heptafluoropropane and impurity standard gas prepared in step 1 into the gas chromatograph at a conventional gas injection volume of 0.2 mL for purity analysis. The experimental results are shown in the chromatogram below. Figure 1 .

[0060] Example 2

[0061] 1. Prepare standard gas containing heptafluoropropane and impurities.

[0062] Standard gases were prepared by extracting different gas volumes of HFC-227ea, 1,1,3,3,3-pentafluoro-1-propene, hexafluoropropene, 1,2,3,3,3-pentafluoro-1-propene, octafluoro-n-butene (trans), octafluoro-n-butene (cis), 1,1,1,2,4,4,4-heptafluoro-2-butene, and 1,1,1,3,3,3-hexafluoropropane according to their percentage content. The resulting standard gases were prepared using 2500 mL gas mixing bottles to obtain heptafluoropropane and impurity standard gases. The content and composition are shown in Table 2.

[0063] Table 2. Standard gases containing heptafluoropropane and impurities prepared in Example 2

[0064]

[0065] 2. Select the column type

[0066] Instrument: 7890 gas chromatograph, Agilent Technologies, equipped with a flame hydrogen detector, manual injection;

[0067] Column type: GASPRO 60m×0.32mm capillary column.

[0068] 3. Set the operating conditions for the gas chromatograph

[0069] The experiment was conducted under the following chromatographic conditions with a standard gas injection volume of 0.2 mL:

[0070] Inlet temperature: 200℃;

[0071] Detector temperature: 220℃;

[0072] Column flow rate: 4 mL / min;

[0073] Injection mode: Split injection;

[0074] Flow split ratio: 40:1;

[0075] Compensating gas flow rate: 20 L / min;

[0076] Temperature program: Hold at 100℃ for 10 minutes, then increase to 180℃ at a rate of 10℃ / min and hold for 6 minutes.

[0077] 4. Detect the sample to be tested.

[0078] Following the column type and chromatographic conditions specified in steps 2 and 3, after the instrument reaches the set state, inject the heptafluoropropane and impurity standard gas prepared in step 1 into the gas chromatograph at a conventional gas injection volume of 0.2 mL for purity analysis. The experimental results are shown in the chromatogram below. Figure 2 .

[0079] Example 3

[0080] 1. Prepare standard gas containing heptafluoropropane and impurities.

[0081] Standard gases were prepared by extracting different gas volumes of HFC-227ea, 1,1,3,3,3-pentafluoro-1-propene, hexafluoropropene, 1,2,3,3,3-pentafluoro-1-propene, octafluoro-n-butene (trans), octafluoro-n-butene (cis), 1,1,1,2,4,4,4-heptafluoro-2-butene, and 1,1,1,3,3,3-hexafluoropropane according to their percentage content. The resulting standard gases were prepared using 2500 mL gas mixing bottles to obtain heptafluoropropane and impurity standard gases. The content and composition are shown in Table 3.

[0082] Table 3. Standard gases containing heptafluoropropane and impurities prepared in Example 3

[0083]

[0084]

[0085] 2. Select the column type

[0086] Instrument: 7890 gas chromatograph, Agilent Technologies, equipped with a flame hydrogen detector, manual injection;

[0087] Column type: GASPRO 60m×0.32mm capillary column.

[0088] 3. Set the operating conditions for the gas chromatograph

[0089] The experiment was conducted under the following chromatographic conditions with a standard gas injection volume of 0.2 mL:

[0090] Inlet temperature: 220℃;

[0091] Detector temperature: 250℃;

[0092] Column flow rate: 6 mL / min;

[0093] Injection mode: Split injection;

[0094] Flow split ratio: 40:1;

[0095] Compensating gas flow rate: 25 mL / min;

[0096] Temperature program: Hold at 120℃ for 6 minutes, then increase to 180℃ at a rate of 5℃ / min and hold for 6 minutes.

[0097] 4. Detect the sample to be tested.

[0098] Following the column type and chromatographic conditions specified in steps 2 and 3, after the instrument reaches the set state, inject the heptafluoropropane and impurity standard gas prepared in step 1 into the gas chromatograph at a conventional gas injection volume of 0.2 mL for purity analysis. The experimental results are shown in the chromatogram below. Figure 3 .

[0099] Example 4

[0100] 1. Prepare standard gas containing heptafluoropropane and impurities.

[0101] Standard gases were prepared by extracting different gas volumes of HFC-227ea, 1,1,3,3,3-pentafluoro-1-propene, hexafluoropropene, 1,2,3,3,3-pentafluoro-1-propene, octafluoro-n-butene (trans), octafluoro-n-butene (cis), 1,1,1,2,4,4,4-heptafluoro-2-butene, and 1,1,1,3,3,3-hexafluoropropane according to their percentage content. The resulting standard gases were prepared using 2500 mL gas mixing bottles to obtain heptafluoropropane and impurity standard gases. The content and composition are shown in Table 4.

[0102] Table 4. Standard gases containing heptafluoropropane and impurities prepared in Example 4

[0103]

[0104] 2. Select the column type

[0105] Instrument: 7890 gas chromatograph, Agilent Technologies, equipped with a flame hydrogen detector, manual injection;

[0106] Column type: DB-5MS 30m×0.25mm quartz capillary column.

[0107] 3. Set the operating conditions for the gas chromatograph

[0108] The experiment was conducted under the following chromatographic conditions with a standard gas injection volume of 0.2 mL:

[0109] Inlet temperature: 250℃;

[0110] Detector temperature: 280℃;

[0111] Column flow rate: 10 mL / min;

[0112] Injection mode: Split injection;

[0113] Flow split ratio: 40:1;

[0114] Compensating gas flow rate: 30 mL / min;

[0115] Temperature program: Hold at 120℃ for 6 minutes, then increase to 200℃ at a rate of 10℃ / min and hold for 6 minutes.

[0116] 4. Detect the sample to be tested.

[0117] Following the column type and chromatographic conditions specified in steps 2 and 3, after the instrument reaches the set state, inject the heptafluoropropane and impurity standard gas prepared in step 1 into the gas chromatograph at a conventional gas injection volume of 0.2 mL for purity analysis. The experimental results are shown in the chromatogram below. Figure 4 .

[0118] Comparative Example 1

[0119] The heptafluoropropane and impurity standard gases prepared in Example 1 were tested according to the method of national standard GB 18614-2012, with a detector temperature of 280℃ and an injection volume of 0.2 mL. The experimental results are shown in the chromatogram. Figure 5 .

[0120] Compared to Figures 1-4 , Figure 5 Early elution time and overlapping peak areas indicate poor separation of substances, resulting in low accuracy and poor separation efficiency. This invention optimizes the national standard method, offering advantages such as aesthetically pleasing peak shapes, suitable analysis time, and good repeatability, making it more suitable for industrial analytical applications.

[0121] Injection volume experiment

[0122] Different injection volumes (0.05 mL, 0.1 mL, 0.2 mL, 0.3 mL, 0.4 mL, 0.5 mL, and 0.6 mL) were used to analyze the purity of heptafluoropropane and impurity standard gases prepared in Example 1. A standard curve was obtained by plotting the injection volume on the x-axis and the peak area on the y-axis. Figure 6 The regression coefficient of the obtained standard curve was 0.9909. The experimental results are shown in Table 5.

[0123] Table 5. Linear relationship between injection volume and peak area

[0124] Injection volume, mL 0.05 0.1 0.2 0.3 0.4 0.5 0.6 Peak area, pA*s 32506 72192 128201 161275 218795 248900 297821

[0125] The results showed that the linearity was good when the injection volume was between 0.05 mL and 0.6 mL.

[0126] Table 6 compares the analytical method of this invention with the analytical method in the national standard:

[0127] Table 6 Comparison of the analytical methods of this invention with those in national standards

[0128]

[0129] Compared with national standards, this invention optimizes seven conditions. After optimization, the chromatographic conditions are more operable, have higher resolution, and fully meet analytical requirements.

[0130] Accuracy Experiment

[0131] Using a conventional gas injection volume of 0.2 mL, the heptafluoropropane and impurity standard gas prepared in Example 1 were injected into the chromatograph for determination. After subtracting the blank, the recovery rate was calculated to verify the accuracy of the optimized method. The calculation results are shown in Table 7, with the recovery rate ranging from 96.7% to 103.7%, indicating that the method of the present invention has high accuracy.

[0132] Table 7 Recovery rate test of each impurity component

[0133] Component Name Theoretical value % Actual measured value % Recovery rate % 1,1,3,3,3-Pentafluoro-1-propene 0.0030 0.00298 99.3 hexafluoropropylene 0.0059 0.00612 103.7 1,2,3,3,3-Pentafluoro-1-propene 0.0045 0.00436 96.9 Octafluorobutene (trans) 0.0015 0.00145 96.7 Octafluorobutene (cis) 0.0025 0.00246 98.4 1,1,1,2,4,4,4-Hepenofluoro-2-butene 0.0026 0.00253 97.3 1,1,1,3,3,3-Hexafluoropropane 0.0089 0.00908 102.0

[0134] Precision test

[0135] Eight parallel tests were conducted using two consecutive batches of samples, and the test results are shown in Table 8.

[0136] Table 8 Precision test of HFC-227ea content (mass fraction, %)

[0137] Sample batch number 1# 2# 1 99.9697 99.9528 2 99.9689 99.9536 3 99.9695 99.9541 4 99.9692 99.9533 5 99.9687 99.9527 6 99.9694 99.9534 7 99.9689 99.9539 8 99.9693 99.9529 average value 99.9692 99.9529 Standard deviation 0.00034 0.00052

[0138] As can be seen from Table 8, the method of the present invention has good repeatability and a small standard deviation, which is between 0.00034 and 0.00052, and can meet the needs of analysis.

Claims

1. A method for analyzing the purity of heptafluoropropane fire extinguishing agent, characterized in that, Includes the following steps: (1) Prepare standard gas of heptafluoropropane and impurities Heptafluoropropane and impurity standard gases were prepared by extracting different gas volumes of HFC-227ea, 1,1,3,3,3-pentafluoro-1-propene, hexafluoropropene, 1,2,3,3,3-pentafluoro-1-propene, trans-octafluoro-n-butene, cis-octafluoro-n-butene, 1,1,1,2,4,4,4-heptafluoro-2-butene, and 1,1,1,3,3,3-hexafluoropropane according to their percentage content. (2) Select one of the following chromatographic column types: GASPRO 30m×0.32mm capillary column, GASPRO 60m×0.32mm capillary column, or DB-5MS 30m×0.25mm quartz capillary column; (3) Set the gas chromatograph analysis conditions, wherein the detector of the gas chromatograph is a flame hydrogen detector; (4) Testing: Using the column type in step (2) and the analytical conditions in step (3), after the gas chromatograph reaches the set state, the purity of the heptafluoropropane and impurity standard gas prepared in step (1) is analyzed. The gas chromatograph analysis conditions set in step (3) include programmed temperature ramping of the column oven. The programmed temperature ramping refers to the following: when using a GASPRO 30m×0.32mm capillary column, maintaining the temperature at 60℃ for 6 minutes, ramping up to 140℃ at 5℃ / min, and maintaining the temperature for 6 minutes; when using a GASPRO 60m×0.32mm capillary column, maintaining the temperature at 100℃ for 10 minutes, ramping up to 180℃ at 10℃ / min, and maintaining the temperature for 6 minutes, or maintaining the temperature at 120℃ for 6 minutes, ramping up to 180℃ at 5℃ / min, and maintaining the temperature for 6 minutes; when using a DB-5MS 30m×0.25mm capillary column, maintaining the temperature at 120℃ for 6 minutes, ramping up to 200℃ at 10℃ / min, and maintaining the temperature for 6 minutes.

2. The method for purity analysis of heptafluoropropane fire extinguishing agent according to claim 1, characterized in that, The mass percentage of HFC-227ea in the heptafluoropropane and impurity standard gas is 97-99%.

3. The method for purity analysis of heptafluoropropane fire extinguishing agent according to claim 1, characterized in that, The gas chromatograph analysis conditions also include: injection port temperature: 180~250℃; detection chamber temperature: 180~280℃; column flow rate: 2~10mL / min; compensation gas flow rate: 20~30 mL / min; injection mode: split injection, split ratio of 40:1.

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