A method for detecting the content of rubber antioxidant in transformer oil
Through the method of solid -phase extraction and chromatography, the problem of low rubber anti -agent in transformer oil in the transformer oil is solved, and effective monitoring and guarantee for the insulation performance of transformer oil.
Patent Information
- Application Number
- CN202211314823.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-26
- Publication Date
- 2025-01-24
- Estimated Expiration
- 2042-10-26
AI Technical Summary
The prior art is difficult to accurately detect the content of rubber anti-aging agent in transformer oil, resulting in a degradation of the insulation performance of transformer oil and affecting the safe and stable operation of the transformer.
The solid-phase extraction method is used to extract the transformer oil using a MEGA-BE-SI solid-phase extraction column and a specific solvent, and the rubber antioxidant is separated, and then quantitatively analyzed by GC-MS or liquid chromatography.
The detection accuracy of the rubber anti -agent content in the transformer oil is improved, and the insulation performance of the transformer oil is effectively monitored and guaranteed.
Smart Images
Figure CN115469037B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of transformer oil detection, and in particular to a method for detecting the content of a rubber antioxidant in transformer oil. Background Art
[0002] Transformer oil is a liquid medium with cooling, arc extinguishing and insulating functions. The excellent performance of transformer oil is an important guarantee for the safe and stable operation of transformers. After large transformers are put into operation, their service life can reach 30 to 40 years. The internal structure of the transformer is complex and there are many types of materials, including transformer oil, copper wires, silicon steel sheets, insulating paper and cardboard, insulating paint and rubber sealing materials. These materials include metal materials, non-metallic materials, both organic small molecules and polymer materials. These materials are immersed in transformer oil for a long time, and under the influence of multiple factors such as electric field, magnetic field and temperature, various complex reactions occur, which have various effects on the performance of transformer oil.
[0003] Rubber sealing materials and rubber pads are indispensable materials inside the transformer. The antioxidants of rubber sealing materials are mainly aniline substances. In recent years, it has been found that the actual transformer oil has become smelly, the dielectric loss factor has increased, and the insulation performance of the transformer oil has decreased. Through a large number of separation and analysis tests, it was finally determined that it was due to the additives in the rubber sealing materials - antioxidants. The life of the transformer is as long as thirty or forty years. The rubber material is immersed in the transformer oil for a long time. The concentration of the antioxidant dissolved in the transformer oil is continuously enriched, resulting in a gradual increase in the impact on the insulation performance of the transformer oil. Therefore, monitoring the content of rubber antioxidants in transformer oil is of great significance to ensure the safe and stable operation of the transformer. Summary of the invention
[0004] The invention provides a method for detecting the content of rubber antioxidant in transformer oil, so as to improve the accuracy of detecting the content of rubber antioxidant in transformer oil.
[0005] In order to solve the above technical problems, the present invention provides a method for detecting the content of rubber antioxidant in transformer oil, comprising the following steps:
[0006] (1) adding n-hexane to a solid phase extraction column containing silica gel filler for activation, wherein the solid phase extraction column is a MEGA-BE-SI solid phase extraction column;
[0007] (2) Adding transformer oil sample into solid phase extraction column;
[0008] (3) eluting the solid phase extraction column with n-hexane;
[0009] (4) Turn on the vacuum pump to drain all the n-hexane on the solid phase extraction column;
[0010] (5) flushing the solid phase extraction column with a solvent, collecting the solvent flushing liquid, and using the solvent to adjust the volume to obtain the flushing liquid to obtain the test liquid, wherein the solvent is methanol and / or acetonitrile;
[0011] (6) Analyze the content of rubber antioxidant in the test liquid by gas chromatography-mass spectrometry or liquid chromatography.
[0012] As a preferred embodiment, the solvent is acetonitrile and methanol in a volume ratio of 2:1.
[0013] As a preferred embodiment, the mass of the transformer oil sample is 2 times or less than the mass of the silica gel filler in the solid phase extractant.
[0014] As a preferred embodiment, the solid phase extraction column is a MEGA-BE-SI solid phase extraction column.
[0015] As a preferred embodiment, the rubber antioxidant is one or more of N-isopropyl-N-phenyl-p-phenylenediamine, N-(1,4-dimethylpentyl)-N-phenyl-p-phenylenediamine, and N-(1-methylheptyl)-N-phenyl-p-phenylenediamine.
[0016] As a preferred embodiment, in step (6), the gas chromatography conditions are as follows: the column oven has a programmed temperature rising function, the starting temperature of the temperature rising program is 50-90°C, the starting holding time is 0 min, the heating rate is 10-20°C / min, the final temperature is 280°C, the final holding time is 2 min, and the helium flow rate is 0.8 mL / min-1.5 mL / min.
[0017] As a preferred embodiment, in step (6), the mass spectrometry conditions are as follows: the ion source is an electron impact source (EI) with an electron energy of 70 eV; the interface temperature is 270°C ± 0.5°C; the collection mode of the mass analyzer is the ion collection mode (SIM), and the quantitative ions are determined according to the specific type of the antioxidant.
[0018] As a preferred embodiment, in step (6), the liquid chromatography conditions are: using a C18 chromatographic separation column and a chromatographic workstation, a flow rate of 1 mL / min, an injection volume of 1 uL, a UV detector detection wavelength of 270 nm, and a mobile phase of methanol and water in a volume ratio of 1:1.
[0019] As a preferred embodiment, in step (3), solvent A with a volume of more than twice the volume of the transformer oil sample is used for elution.
[0020] Compared with the prior art, the present invention has the following beneficial effects:
[0021] Transformer oil is a complex mixture of alkanes, cycloalkanes and aromatic hydrocarbons. To detect rubber antioxidants, it is first necessary to separate them from the complex transformer oil bulk molecules. Failure to separate them will cause the chromatographic absorption peaks of low-concentration rubber antioxidants to be covered by high-concentration transformer oil bulk molecules, making them undetectable or inaccurately detected. The present application uses solid phase extraction to extract the rubber antioxidant in transformer oil, and uses a specific solvent to fix the rubber antioxidant in the transformer oil in the filler with a high probability, efficiently separates the rubber antioxidant from the transformer oil, and then quantitatively detects the separated rubber antioxidant components, thereby improving the detection accuracy of the rubber antioxidant in the transformer oil. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is the standard curve of the N-isopropyl-N-phenyl-p-phenylenediamine standard solution in the gas chromatography of the embodiment of the present application;
[0023] Figure 2 This is the standard curve of the N-isopropyl-N-phenyl-p-phenylenediamine standard solution in the liquid chromatography of the embodiment of the present application;
[0024] Figure 3 The gas chromatography-mass spectrometry (GC-MS) detection results obtained after the transformer oil in Application Example 1 of this application is tested for the content of rubber antioxidant using the scheme of Example 1 (the upper figure is a gas chromatography image, and the lower figure is a mass spectrometry image);
[0025] Figure 4 The mass spectrometry detection results obtained after the transformer oil in Application Example 1 of this application is detected by the scheme of Example 1 for detecting the content of rubber antioxidant (the upper figure is the mass spectrometry image of N-isopropyl-N-phenyl-p-phenylenediamine in the flushing liquid, and the lower figure is the mass spectrometry image of N-isopropyl-N-phenyl-p-phenylenediamine in the multi-spectral library);
[0026] Figure 5 The gas chromatography-mass spectrometry (GC-MS) detection results obtained after the transformer oil in Application Example 1 of this application is tested for the content of rubber antioxidant using the scheme of Comparative Example 1 (the upper figure is a gas chromatography image, and the lower figure is a mass spectrometry image);
[0027] Figure 6 The mass spectrometry detection results obtained after the transformer oil in Application Example 1 of the present application was detected for the rubber antioxidant content using the Comparative Example 1 scheme (the upper figure is the mass spectrometry image of N-isopropyl-N-phenyl-p-phenylenediamine in the flushing liquid, and the lower figure is the mass spectrometry image of N-isopropyl-N-phenyl-p-phenylenediamine in the multi-spectral library). DETAILED DESCRIPTION
[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0029] Embodiment 1
[0030] A method for detecting the content of rubber antioxidant in transformer oil comprises the following steps:
[0031] (1) Accurately measure 5 ml of n-hexane with a pipette and add it to a MEGA-BE-SI solid phase extraction column containing silica gel filler for activation. The solid phase extraction column is selected from Agilent brand product number 12256008;
[0032] (2) Add transformer oil sample containing rubber antioxidants, including N-isopropyl-N-phenyl-p-phenylenediamine, N-(1,4-dimethylpentyl)-N-phenyl, and N-(1-methylheptyl)-N-phenyl-p-phenylenediamine at a concentration of 30 mg / L, and use a pipette to accurately measure 5 ml (V 1 ) Transformer oil sample, add solid phase extraction column;
[0033] (3) Use a pipette to accurately measure 10 ml of n-hexane and add it to the solid phase extraction column for elution;
[0034] (4) Turn on the vacuum pump to drain all the n-hexane solvent on the solid phase extraction column;
[0035] (5) Use a pipette to accurately measure 5 ml of methanol to rinse the solid phase extraction column, collect this part of the solvent rinse, and dilute it to 5 mL (V) with methanol. 2 ), obtain the flushing solution for standby use;
[0036] (6) analyzing the content of rubber antioxidant in the flushing liquid by gas chromatography-mass spectrometry;
[0037] Preparation of standard solution: Taking N-isopropyl-N-phenyl-p-phenylenediamine as an example, first prepare 1000 mg / L methanol mother solution, weigh N-isopropyl-N-phenyl-p-phenylenediamine and put it into a 25 mL volumetric flask, dilute to 25 mL with methanol, the concentration of the standard solution is shown in Table 1, analyze the standard solutions of different concentrations, and record the response values (peak areas, as shown in Table 2), and obtain the following by measuring 4 kinds of standard substances with concentrations of 5-100 mg / L. Figure 1 The standard curve is shown.
[0038] Table 1 - Standard solutions of N-isopropyl-N-phenyl-p-phenylenediamine at different concentrations in gas chromatography
[0039]
[0040]
[0041] Table 2 - Response values of N-isopropyl-N-phenyl-p-phenylenediamine standard solution in gas chromatography
[0042] Serial number Standard solution concentration mg / L Absorption peak intensity 1 5 6866 2 20 35635 3 50 102074 4 100 217703
[0043] The gas chromatography conditions are as follows: the column oven has a programmed temperature function, the starting temperature of the temperature program is 90°C, the starting holding time is 0 min, the heating rate is 20°C / min, the final temperature is 280°C, the final holding time is 2 min, and the helium flow rate is 0.8 mL / min-1.5 mL / min.
[0044] The mass spectrometry conditions were:
[0045] Ion source: electron impact source (EI), electron energy 70eV;
[0046] Interface temperature: 270℃±0.5℃;
[0047] Mass analyzer: The acquisition mode selects the ion acquisition mode (SIM), and the quantitative ion is determined according to the specific type of antioxidant;
[0048] Data system: has the functions of controlling, monitoring, acquiring and storing analytical data.
[0049] (7) The flushing liquid obtained in step (5) is subjected to three parallel tests according to the method of step (6), and the average value is taken. The flushing liquid sample concentration C obtained by the test is 1 Then calculate the rubber antioxidant concentration C (mg / L) in transformer oil according to the following formula: C = C 1 *V 2 / V 1 In this embodiment, the concentration C of the rubber antioxidant in the transformer oil is equal to the concentration C of the flushing liquid sample. 1 .
[0050] Embodiment 2
[0051] A method for detecting the content of rubber antioxidant in transformer oil, wherein each step and the reagents and process parameters used in each step are the same as those in Example 1, except that in step (5), acetonitrile is used instead of methanol.
[0052] Embodiment 3
[0053] A method for detecting the content of a rubber antioxidant in transformer oil, wherein each step and the reagents and process parameters used in each step are the same as those in Example 1, except that in step (6), the rinsing liquid is subjected to high performance liquid chromatography for analyzing the content of the rubber antioxidant, a C18 chromatographic separation column and a chromatographic workstation are used, the flow rate is 1 mL / min, the injection volume is 1 uL, the detection wavelength of an ultraviolet detector is 270 nm, and the mobile phase is methanol and water in a volume ratio of 1:1;
[0054] Preparation of standard solution: Taking N-isopropyl-N-phenyl-p-phenylenediamine as an example, first prepare 1000 mg / L methanol mother solution, weigh N-isopropyl-N-phenyl-p-phenylenediamine and put it into a 25 mL volumetric flask, dilute to 25 mL with methanol, the concentration of the standard solution is shown in Table 3, analyze the standard solutions of different concentrations, and record the response values (peak areas, as shown in Table 4), and obtain the following by measuring 4 kinds of standard substances with concentrations of 5-100 mg / L. Figure 1 The standard curve is shown.
[0055] Table 3 - Standard solutions of different concentrations of N-isopropyl-N-phenyl-p-phenylenediamine in liquid chromatography
[0056] Serial number Standard solution concentration mg / L Methanol mother liquor mL Methanol volume mL 1 5 0.125 25 2 20 0.5 25 3 50 1.25 25 4 100 2.5 25
[0057] Table 4 - Response values of N-isopropyl-N-phenyl-p-phenylenediamine standard solution in liquid chromatography
[0058] Serial number Standard solution concentration mg / L Response value (peak area) 1 5 190523 2 20 785282 3 50 1912106 4 100 3428336
[0059] Embodiment 4
[0060] A method for detecting the content of rubber antioxidant in transformer oil, wherein each step and the reagents and process parameters used in each step are the same as those in Example 1, except that in step (5), a mixed solvent is used instead of methanol, and the mixed solvent is a mixture of acetonitrile and methanol in a volume ratio of 2:1.
[0061] Comparative Example 1
[0062] A method for detecting the content of a rubber antioxidant in transformer oil comprises the following steps: using a pipette to accurately measure 5 ml of a transformer oil sample containing a rubber antioxidant and add the sample to a 50 ml centrifuge tube, wherein the rubber antioxidant comprises N-isopropyl-N-phenyl-p-phenylenediamine, N-(1,4-dimethylpentyl)-N-phenyl, and N-(1-methylheptyl)-N-phenyl-p-phenylenediamine, all with a concentration of 30 mg / L; then adding 7.5 ml of methanol; covering the tube with a lid; mechanically shaking the tube for 15 minutes; centrifuging the tube at a speed of 3000 rpm for 5 minutes; taking the supernatant liquid and subjecting it to gas chromatography-mass spectrometry analysis; performing three parallel tests and taking an average value;
[0063] The gas chromatography conditions are as follows: the column oven has a programmed temperature function, the starting temperature of the temperature program is 90°C, the starting holding time is 0 min, the heating rate is 20°C / min, the final temperature is 280°C, the final holding time is 2 min, and the helium flow rate is 0.8 mL / min-1.5 mL / min.
[0064] The mass spectrometry conditions were:
[0065] Ion source: electron impact source (EI), electron energy 70eV;
[0066] Interface temperature: 270℃±0.5℃;
[0067] Mass analyzer: The acquisition mode selects the ion acquisition mode (SIM), and the quantitative ion is determined according to the specific type of antioxidant;
[0068] Data system: has the functions of controlling, monitoring, acquiring and storing analytical data.
[0069] Comparative Example 2
[0070] A method for detecting the content of rubber antioxidant in transformer oil, wherein each step and the reagents and process parameters used in each step are the same as those in Example 1, except that in steps (1), (3) and (4), acetone is used instead of n-hexane.
[0071] Comparative Example 3
[0072] A method for detecting the content of rubber antioxidant in transformer oil, wherein each step, the reagents used in each step, and the process parameters are the same as those in Example 1, except that the solid phase extraction column is a BOND ELUT-C18 solid phase extraction column.
[0073] Test analysis results
[0074] Table 5 - Test results of rubber antioxidant in transformer oil samples in Examples 1-4 and Comparative Examples 1-3
[0075]
[0076]
[0077] Application Example 1
[0078] According to the standard "JB / T 8448.1-2018 Technical Conditions for Sealing Products for Transformer Products Part 1: Rubber Sealing Products", select 65cm 2The rubber sealing product with a surface area of 1000 g was dried at a certain temperature, immersed in 800 mL of transformer oil, and aged at a certain temperature for 164 hours. The transformer oil samples after the above treatment were tested using the detection methods of Example 1 and Comparative Example 1, and the test results are as follows: Figure 2-5 shown.
[0079] like Figure 3-4 As shown, after using the method of separating transformer oil and rubber antioxidant therein by solid phase extraction column in Example 1 of the present application, the main peak spectrum in the gas chromatogram is the rubber antioxidant component, indicating that the transformer oil content in the flushing liquid is small, the separation effect of rubber antioxidant and transformer oil is good, and it does not affect the test result, and the test result is 78.38 mg / L. Figure 5-6 As shown, after using the liquid-liquid extraction method in the scheme of comparative document 1 to separate the transformer oil and the rubber antioxidant therein, the gas chromatogram shows that the separation of the transformer oil and the rubber antioxidant in the flushing liquid is poor, and the rubber antioxidant is not completely separated from the transformer oil. At the same time, the peak spectrum of the transformer oil covers the peak spectrum of the rubber antioxidant, affecting the accuracy of the detection.
[0080] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for detecting the content of rubber antioxidant in transformer oil, characterized in that: The following steps are involved: (1) adding n-hexane to a solid phase extraction column containing silica gel filler for activation, wherein the solid phase extraction column is a MEGA-BE-SI solid phase extraction column; (2) Adding transformer oil sample into solid phase extraction column; (3) eluting the solid phase extraction column with n-hexane; (4) Turn on the vacuum pump to drain all the n-hexane on the solid phase extraction column; (5) flushing the solid phase extraction column with a solvent, collecting the solvent flushing liquid, and diluting the volume with the solvent to obtain a test solution, wherein the solvent is methanol and acetonitrile in a volume ratio of 2:1; (6) Analyze the content of rubber antioxidant in the test liquid by gas chromatography-mass spectrometry or liquid chromatography.
2. The method for detecting the content of rubber antioxidant in transformer oil according to claim 1, characterized in that: The mass of the transformer oil sample is 2 times or less than the mass of the silica gel filler in the solid phase extractant.
3. The method for detecting the content of rubber antioxidant in transformer oil according to claim 1, characterized in that: The rubber antioxidant is one or more of N-isopropyl-N-phenyl-p-phenylenediamine, N-(1,4-dimethylpentyl)-N-phenyl-p-phenylenediamine, and N-(1-methylheptyl)-N-phenyl-p-phenylenediamine.
4. The method for detecting the content of rubber antioxidant in transformer oil according to claim 1, characterized in that: In step (6), the gas chromatography conditions are as follows: the column oven has a programmed temperature function, the starting temperature of the temperature program is 50-90°C, the starting holding time is 0 min, the heating rate is 10-20°C / min, the final temperature is 280°C, the final holding time is 2 min, and the helium flow rate is 0.8 mL / min-1.5 mL / min.
5. The method for detecting the content of rubber antioxidant in transformer oil according to claim 1, characterized in that: In step (6), the mass spectrometry conditions are as follows: the ion source is an electron impact source (EI), and the electron energy is 70 eV; the interface temperature is 270°C ± 0.5°C; the collection mode of the mass analyzer selects the ion collection mode (SIM), and the quantitative ion is determined according to the specific type of the antioxidant.
6. The method for detecting the content of rubber antioxidant in transformer oil according to claim 1, characterized in that: In step (6), the liquid chromatography conditions are: using a C18 chromatographic separation column, a chromatographic workstation, a flow rate of 1 mL / min, an injection volume of 1 uL, a UV detector detection wavelength of 270 nm, and a mobile phase of methanol and water in a volume ratio of 1:
1.
7. The method for detecting the content of rubber antioxidant in transformer oil according to claim 1, characterized in that: In step (3), n-hexane with a volume of 2 times or more of the transformer oil sample is used for elution.