A method for separating and analyzing organic polar substances in mineral transformer oil

Abstract

The invention discloses a separation and analysis method of organic polar substances in mineral transformer oil, and relates to the technical field of transformer oil detection. The method comprises the following steps: activating a solid phase extraction column with petroleum ether, and adding a transformer oil sample; eluting and draining the solid phase extraction column with petroleum ether; rinsing the solid phase extraction column with acetonitrile, and collecting rinsing liquid A; repeating the above steps to obtain rinsing liquid B; mixing rinsing liquids A and B, and using gas chromatography-mass spectrometry to analyze organic polar substances, and screen polar pollutants. The present application uses a solid phase extraction column to efficiently separate the transformer oil body and organic polar components in the mineral transformer oil, which can avoid the chromatographic absorption peak of the low-concentration organic polar substance detection being covered by the chromatographic peak of the high-concentration transformer oil body molecule, improve the analysis accuracy, and timely discover abnormal components such as polar pollutants in the transformer oil, thereby ensuring the insulation performance of the transformer oil and the safe and stable operation of the power equipment.

Description

Technical Field

[0001] The invention relates to the field of transformer oil detection, in particular to a separation and analysis method for organic polar substances in mineral transformer oil. Background Art

[0002] Mineral 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. 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] The above-mentioned materials are immersed in transformer oil for a long time, causing some components in the materials to dissolve in the transformer oil, affecting the performance of the transformer oil, especially polar substances, collectively referred to as polar pollutants, which will form small conductive bridges in the electric field, thereby reducing the insulation performance of the transformer oil, resulting in a decrease in the insulation resistance of the main transformer, which is prone to discharge and breakdown failures of the main transformer. Therefore, it is very important to study the separation and analysis methods of polar pollutants in transformer oil.

[0004] Mineral transformer oil is a complex mixture of alkanes, cycloalkanes and aromatic hydrocarbons, which is a non-polar substance. Polar pollutants are mainly small molecular compounds, and the concentration is very low, basically at the mg / kg level. Therefore, it is very difficult to detect trace polar pollutants from the huge transformer oil molecules, just like looking for a needle in a haystack. Secondly, polar pollutants are unknown substances. Separation is the first step, and identification is also required. Therefore, all methods that require standard substances for detection are not applicable to the detection of polar pollutants. Therefore, the separation and analysis of polar pollutants in transformer oil are extremely difficult, and the operation, maintenance and research of transformer oil are of great significance. Summary of the invention

[0005] The invention provides a separation and analysis method for organic polar substances in mineral transformer oil, so as to improve the separation effect and qualitative detection capability of polar pollutants in transformer oil and avoid missed detection of low-content organic polar substances.

[0006] In order to solve the above-mentioned technical problems, the present invention provides a separation and analysis method of organic polar substances in a mineral transformer oil, comprising the following steps:

[0007] (1) adding petroleum ether 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, and immediately adding the transformer oil sample to the solid phase extraction column after the petroleum ether liquid level in the solid phase extraction column disappears;

[0008] (2) After the transformer oil level in the solid phase extraction column disappears, the solid phase extraction column is eluted with petroleum ether. After the eluent level disappears, a vacuum pump is turned on to drain all the petroleum ether on the solid phase extraction column to obtain an eluent;

[0009] (3) flushing the solid phase extraction column with acetonitrile and collecting the flushing liquid A;

[0010] (4) Repeating the operations of steps (1), (2) and (3) with the eluent discharged from step (2), and using a new solid phase extraction column to obtain a flushing solution B;

[0011] (5) After the flushing liquids A and B are mixed and concentrated, the organic polar matter is analyzed by gas chromatography-mass spectrometry to screen for polar pollutants;

[0012] In step (5), 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 10°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.

[0013] As a preferred embodiment, the solvent A is petroleum ether and n-hexane in a volume ratio of (1-2):1.

[0014] 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.

[0015] As a preferred embodiment, in step (5), the gas chromatography conditions are as follows: the capillary column is a stationary phase of 5% phenyl polysiloxane and 95% methyl polysiloxane, with a length of 30 m, an inner diameter of 0.25 mm, and a film thickness of 0.25 μm.

[0016] As a preferred solution, in step (5), 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 acquisition mode of the mass analyzer is the full scan mode SCAN, and the acquisition range is 45-800 m / z.

[0017] As a preferred solution, in step (2), solvent A with a volume of more than twice the volume of the transformer oil sample is used for elution.

[0018] As a preferred embodiment, the organic polar substance is one or more of 2,4-di-tert-butyl-p-cresol, 2,4-di-tert-butylphenol, phthalate plasticizer, metal deactivator, and furfural.

[0019] As a preferred embodiment, the metal passivator is benzotriazole or its derivatives.

[0020] As a preferred embodiment, the metal passivator is Irgamet 39.

[0021] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0022] The present application adopts a solid phase extraction column to efficiently separate the organic polar components and the transformer oil body in mineral transformer oil; the separated organic polar components are then subjected to a qualitative analysis of polar pollutants by gas chromatography-mass spectrometry technology, which can avoid the chromatographic absorption peaks during the detection of organic polar substances being reflected by the transformer, improve the analysis accuracy of polar pollutants, prevent the omission of some low-content organic polar substances, and provide a basic test for the research on improving the quality of transformer oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : be the gas chromatography-mass spectrometry chromatographic detection result of transformer oil in Application Example 1 of the present invention (the upper figure is the gas chromatographic image of transformer oil, and the lower figure is the mass spectrum image of 2,4-di-tert-butyl-p-cresol in transformer oil);

[0024] Figure 2 : be the mass spectrum image result of transformer oil in Application Example 1 of the present invention (the upper figure is the mass spectrum image in transformer oil, and the lower figure is the mass spectrum image of 2,4-di-tert-butyl-p-cresol in multi-spectral library);

[0025] Figure 3 : be the gas chromatography-mass spectrometry chromatographic detection result of transformer oil in Application Example 1 of the present invention (the upper figure is the gas chromatographic image of transformer oil, and the lower figure is the mass spectrum image of phthalates in transformer oil);

[0026] Figure 4 : be the mass spectrum image result of transformer oil in Application Example 1 of the present invention (the upper figure is the mass spectrum image of phthalates in transformer oil, and the lower figure is the mass spectrum image of phthalates in multi-spectral library);

[0027] Figure 5 : be the gas chromatography-mass spectrometry chromatographic detection result of transformer oil in Application Example 2 of the present invention (the upper figure is the gas chromatographic image of transformer oil, and the lower figure is the mass spectrum image of 2.4-di-tert-butylphenol in transformer oil);

[0028] Figure 6: be the mass spectrum image result of transformer oil in Application Example 2 of the present invention (the upper figure is the mass spectrum image in transformer oil, and the lower figure is the mass spectrum image of 2.4-di-tert-butylphenol in the multi-spectral library);

[0029] Figure 7 : be the gas chromatography-mass spectrometry chromatographic detection result of transformer oil in Application Example 2 of the present invention (the upper figure is the gas chromatographic image of transformer oil, and the lower figure is the mass spectrum image of phthalates in transformer oil);

[0030] Figure 8 : be the mass spectrum image result of transformer oil in Application Example 2 of the present invention (the upper figure is the mass spectrum image of phthalates in transformer oil, and the lower figure is the mass spectrum image of phthalates in multi-spectral library);

[0031] Fig. 9 : be the gas chromatography-mass spectrometry chromatographic detection result of transformer oil in Application Example three of the present invention (the upper figure is the gas chromatographic image of transformer oil, and the lower figure is the mass spectrum image of 2,4-di-tert-butyl-p-cresol in transformer oil);

[0032] Fig.10 : be the mass spectrum image result of transformer oil in Application Example three of the present invention (the upper figure is the mass spectrum image in transformer oil, and the lower figure is the mass spectrum image of 2,4-di-tert-butyl-p-cresol in multi-spectral library);

[0033] Fig.11 : It is the gas chromatography-mass spectrometry (GC-MS) chromatographic detection result of transformer oil in Application Example 3 of the present invention (the upper figure is the gas chromatography image of transformer oil, and the lower figure is the mass spectrum image of 2,4-di-tert-butyl-p-cresol derivative in transformer oil);

[0034] Fig.12 : is the mass spectrum image result of transformer oil in Application Example 3 of the present invention (the upper figure is the mass spectrum image in transformer oil, and the lower figure is the mass spectrum image of 2,4-di-tert-butyl-p-cresol derivative in the multi-spectral library). DETAILED DESCRIPTION

[0035] 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.

[0036] Embodiment 1

[0037] A separation and analysis method for organic polar substances in mineral transformer oil comprises the following steps:

[0038] (1) Prepare a transformer oil sample containing polar substances at a concentration of 50 mg / L, wherein the polar substances are 2,4-di-tert-butyl-p-cresol, Irgamet 39, and phthalates, and separate and analyze the transformer oil sample;

[0039] (2) Accurately measure 5 ml of petroleum ether with a pipette, add it to a solid phase extraction column containing silica gel filler for activation, and immediately add the transformer oil sample after the solvent liquid level in the solid phase extraction column disappears, accurately measure 5 ml (V1) of the transformer oil sample with a pipette, and add it to the solid phase extraction column, which is selected from the MEGA-BE-SI solid phase extraction column with the item number 12256008 in the Agilent brand;

[0040] (3) After the transformer oil level in the solid phase extraction column disappears, use a pipette to accurately measure 10 ml of petroleum ether and add it to the solid phase extraction column for elution. After the eluent level disappears, turn on the vacuum pump to completely drain the petroleum ether solvent on the solid phase extraction column to obtain an eluent;

[0041] (4) Use a pipette to accurately measure 5 ml of acetonitrile to rinse the solid phase extraction column, collect this portion of the solvent rinse liquid, and dilute the volume to 5 mL (V2) with acetonitrile to obtain rinse liquid A;

[0042] (5) Repeating steps (3) and (4) with the eluent discharged from step (3) and using a new solid phase extraction column to obtain a flushing solution B;

[0043] (6) After the flushing solutions A and B are mixed, concentrated, and fixed to 5 mL, organic polar matter analysis is performed using a gas chromatography-mass spectrometry (GC-MS) to screen for polar pollutants;

[0044] The gas chromatography conditions are as follows: the capillary column is a 5% phenyl polysiloxane and 95% methyl polysiloxane stationary phase, with a length of 30 m, an inner diameter of 0.25 mm, and a film thickness of 0.25 μm; the column oven has a programmed temperature rising function, the starting temperature of the temperature rising program is 90°C, the starting holding time is 0 min, the heating rate is 10°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.

[0045] The mass spectrometry conditions were:

[0046] Ion source: electron impact source (EI), electron energy 70eV;

[0047] Interface temperature: 270℃±0.5℃;

[0048] Mass analyzer: The acquisition mode is selected as full scan mode (SCAN), and the acquisition range is 45-800 m / z;

[0049] Data system: has the functions of controlling, monitoring, acquiring and storing analytical data.

[0050] Comparative Example 1

[0051] A method for separating and analyzing organic polar substances in mineral 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 acetone is used instead of petroleum ether.

[0052] Comparative Example 2

[0053] A method for separating and analyzing organic polar substances in mineral 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 n-hexane is used instead of petroleum ether.

[0054] Comparative Example 3

[0055] A method for separating and analyzing organic polar matter in mineral 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 the filler of the solid phase extraction column is a BONDELUT-C18 solid phase extraction column.

[0056] Comparative Example 4

[0057] A method for separating and analyzing organic polar substances in mineral 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 step (5) is not performed, and in step (6), after the flushing liquid A is directly fixed to volume, the organic polar substances are analyzed by gas chromatography-mass spectrometry to screen polar pollutants.

[0058] Test analysis results

[0059] The flushing liquid in Example 1 and Comparative Examples 1-4 were tested three times in parallel according to the method of step (6), and the average value was taken. The concentration C1 of the flushing liquid sample obtained by the test was used to calculate the concentration C (mg / L) of polar substances in the transformer oil according to the following formula: C=C1*V2 / V1. The test results of the transformer oil samples are shown in Table 1.

[0060] Table 1 - Detection results of polar substances in transformer oil samples in Example 1 and Comparative Examples 1-4

[0061]

[0062]

[0063] Combining the test results of Example 1 and Comparative Examples 1-2 in Table 1, it can be seen that when acetone or n-hexane is used as the activation solvent of the solid phase extraction column, the separation efficiency of some organic polar substances in the transformer oil sample and the transformer oil body is low, which will lead to the omission of low-content organic polar substances in the transformer oil.

[0064] Combining the test results of Example 1 and Comparative Example 4 in Table 1, it can be seen that the effects of the transformer oil sample after one or two separations by the solid phase extraction column are different. In the first separation, the separation effect of some organic polar substances is poor, which easily leads to the omission of low-content organic polar substances, while the secondary separation can ensure the efficient separation of low-concentration organic polar substances, thereby improving the accuracy of detection.

[0065] Application Example 1

[0066] Separation and analysis of transformer oil in 500kV Yanda Station #2 main transformer (taking #2 main transformer phase A as an example): Yanda Station #2 main transformer was put into operation in 2019. The transformer oil of phase A of Yanda Station #2 main transformer was tested using the separation and analysis method of Example 1 of this application. The results are as follows: Figure 1-2 As shown in the gas chromatogram, a large amount of 2,4-di-tert-butyl-p-cresol appeared; Figure 3-4 As shown, the gas chromatographic spectrum also shows a small amount of phthalates, which are polar pollutant components.

[0067] Application Example 2

[0068] Separation and analysis of transformer oil in 500kV Zongjiang Station #2 main transformer (taking #2 main transformer phase A as an example): Zongjiang Station #2 main transformer was put into operation in 2018. The transformer oil of phase A of Zongjiang Station #2 main transformer was tested using the separation and analysis method of Example 1 of the present application. The results are as follows: Figure 5-6 As shown, 2.4-di-tert-butylphenol appears in the gas chromatogram; Figure 7-8 As shown, the gas chromatographic spectrum also contains phthalates, which are polar pollutant components.

[0069] Application Example 3

[0070] Separation analysis of transformer oil in 500kV Wuyi Station #3 main transformer (taking #3 main transformer phase A as an example): Wuyi Station #3 main transformer was put into operation in 2013. The transformer oil of Wuyi Station #3 main transformer phase A was tested using the separation analysis method of Example 1 of the present application. The results are as follows: Figure 9-10 As shown, 2,4-di-tert-butyl-p-cresol appears in the gas chromatogram; Figure 11-12 As shown, the gas chromatographic spectrum also showed 2,4-di-tert-butyl-p-cresol derivatives, and no polar pollutant components were found.

[0071] 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 separating and analyzing organic polar substances in mineral transformer oil, characterized in that: The following steps are involved: (1) adding petroleum ether 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, and immediately adding the transformer oil sample to the solid phase extraction column after the petroleum ether liquid level in the solid phase extraction column disappears; (2) After the transformer oil level in the solid phase extraction column disappears, the solid phase extraction column is eluted with petroleum ether. After the eluent level disappears, the vacuum pump is turned on to drain all the petroleum ether on the solid phase extraction column to obtain the eluent; (3) Rinse the solid phase extraction column with acetonitrile and collect the rinse liquid A; (4) Repeating the operations of steps (1), (2) and (3) with the eluent discharged from step (2), and using a new solid phase extraction column to obtain a flushing solution B; (5) After the flushing liquids A and B are mixed and concentrated, the organic polar matter is analyzed by gas chromatography-mass spectrometry to screen for polar pollutants; In step (5), 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 90°C, the starting holding time is 0 min, the heating rate is 10°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; The organic polar substance is one or more of 2,4-di-tert-butyl-p-cresol, 2,4-di-tert-butylphenol, phthalate plasticizer, benzotriazole or its derivative metal passivator; In step (5), the gas chromatography conditions are as follows: the capillary column is a 5% phenyl polysiloxane and 95% methyl polysiloxane stationary phase, with a length of 30 m, an inner diameter of 0.25 mm, and a film thickness of 0.25 μm.

2. The method for separation and analysis of organic polar substances in a mineral transformer oil as claimed in 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 separation and analysis of organic polar substances in a mineral transformer oil as claimed in claim 1, characterized in that: In step (5), 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 acquisition mode of the mass analyzer is selected as the full scan mode SCAN, and the acquisition range is 45-800 m / z.

4. The method for separation and analysis of organic polar substances in a mineral transformer oil as claimed in claim 1, characterized in that: In step (2), petroleum ether with a volume of 2 times or more of the transformer oil sample is used for elution.

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