A method for rapid separation and detection of a fault diagnosis agent in transformer insulating oil

Abstract

The application belongs to the technical field of power equipment fault diagnosis, and particularly relates to a rapid separation and detection method of a fault diagnosis agent in transformer insulating oil. The rapid detection method comprises S1. sample pretreatment, S2. thin layer chromatography rapid separation and purification, and S3. chiral high performance liquid chromatography accurate quantitative detection. The method combines the rapid intuition of TLC and the accurate specificity of chiral HPLC, can provide qualitative information of the diagnosis agent and accurate quantitative data, and provides comprehensive data support for evaluating the fault state of the transformer.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power equipment fault diagnosis, and particularly relates to a rapid separation and detection method of a fault diagnosis agent in transformer insulating oil. BACKGROUND

[0002] The power transformer is the core equipment of the power grid, and its operation reliability is crucial. At present, the fault diagnosis method based on dissolved gas analysis (DGA) in oil has a lag, and it is difficult to realize early warning of acute failure. In order to overcome this bottleneck, in recent years, researchers have proposed the strategy of adding specific fault diagnosis agents to the insulating oil. These diagnosis agents will undergo characteristic changes under the action of fault energy, thereby serving as an early and sensitive indication signal of fault occurrence.

[0003] However, the successful application of this strategy faces a key technical challenge: how to quickly and efficiently separate and accurately detect trace amounts or trace amounts of diagnosis agents from the transformer insulating oil matrix with complex components and serious background interference. Therefore, it is urgent to develop an analysis method that can quickly separate and accurately detect chiral diagnosis agents with high sensitivity and high selectivity, in order to support the practical application of the new transformer early fault warning technology based on diagnosis agents. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a transformer insulating oil fault diagnosis agent separation and detection method which is simple to operate, fast and efficient, and highly specific. Specifically, it is an analysis method that combines thin layer chromatography (TLC) for rapid separation and qualitative analysis, and uses chiral high performance liquid chromatography (HPLC) for accurate quantitative detection, in order to realize rapid screening and accurate quantification of diagnosis agents.

[0005] To this end, the present application provides a rapid separation and detection method of a transformer insulating oil fault diagnosis agent, the rapid detection method comprising:

[0006] S1. Sample pretreatment:

[0007] Take the transformer insulating oil sample to be tested, add a first organic solvent for dilution, and obtain a sample to be separated and purified;

[0008] S2. Thin layer chromatography (TLC) rapid separation and purification:

[0009] a. Plate preparation;

[0010] b. Sample application;

[0011] c. Development;

[0012] d. Color development: After development, dry; if the fault diagnostic agent itself has no fluorescence, select a color developing agent for color development; if the fault diagnostic agent has fluorescence, directly observe under ultraviolet light;

[0013] e. Qualitative analysis: By calculating the Rf value of the target spot, and comparing with the standard, the rapid qualitative identification and preliminary separation effect evaluation of the fault diagnostic agent and its possible products are realized;

[0014] f. Separation and purification: The silica gel spot containing the target standard is scraped off, and dissolved in ethyl acetate to obtain the standard solution by suction filtration;

[0015] g. Concentration: Remove the solvent to obtain the standard of analytical purity;

[0016] S3. Chiral high performance liquid chromatography (HPLC) precise quantitative detection:

[0017] a. Chromatographic conditions:

[0018] Chromatographic column: Chiral stationary phase chromatographic column, such as Chiralpak IC, AD-H, OD-H, etc.

[0019] b. Sample analysis: The standard prepared by S2 treatment and separation and purification is dissolved in a second organic solvent to prepare a test solution, which is injected into a high performance liquid chromatography system;

[0020] c. Quantitative analysis: The content of the diagnostic agent in the insulating oil is quantitatively analyzed; the enantiomeric excess percentage is quantitatively calculated by the peak area ratio of chiral compounds;

[0021] The fault diagnostic agent is a diether organic compound with a chiral center, which will change its configuration under the action of fault energy and generate products different from the original diagnostic agent in chiral properties or chromatographic behavior.

[0022] As a preferred solution, in step S1 of the above method for rapid detection of fault diagnostic agent in transformer insulating oil, the first organic solvent is at least one of n-hexane and petroleum ether. For example, 100 uL of transformer oil sample containing fault diagnostic agent is diluted with 50 uL of n-hexane to ensure that the insulating oil is fully diluted and forms a uniform, low-viscosity separation solution, while avoiding excessive solvent leading to reduced subsequent thin layer chromatography development efficiency.

[0023] As a preferred solution, in step S2a of the above method for rapid separation and detection of fault diagnostic agent in transformer insulating oil, the plate is selected to be a silica gel thin layer chromatography plate. The stationary phase of the silica gel thin layer chromatography plate can be conventional silica gel GF254 with a thickness of 0.2-0.25 mm.

[0024] As a preferred solution, in the step b of the step S2 of the method for rapid separation and detection of the fault diagnostic agent in the transformer insulating oil, the sample obtained in the step S1 is spotted on the thin layer plate. The spotting position can be located at 1.5-2.0 cm from the bottom edge of the thin layer plate, the spotting amount can be controlled at about 0.1-0.5 mL of the insulating oil sample, the spotting diameter is ≤2 mm to avoid spot diffusion, and the spotting tool can be a micro-injection needle or a glass capillary to ensure the uniformity of the spotting.

[0025] As a preferred solution, in the step c of the step S2 of the method for rapid separation and detection of the fault diagnostic agent in the transformer insulating oil, the thin layer plate after spotting is placed in a developing cylinder for development. The developing cylinder needs to be saturated with the developing agent for 15-30 minutes in advance to reduce the edge effect.

[0026] As a preferred solution, in the step c of the step S2 of the method for rapid separation and detection of the fault diagnostic agent in the transformer insulating oil, the developing agent is one or both of petroleum ether and ethyl acetate; for example, pure petroleum ether, or petroleum ether: ethyl acetate = 100:1, v / v. When the polarity of the diagnostic agent is low, pure petroleum ether (boiling range 60-90°C) is preferred as the developing agent; when the polarity difference between the target and impurities is small, a mixed solvent of petroleum ether and ethyl acetate (for example, volume ratio 100:1 to 50:1, preferably 100:1) is used to adjust the developing selectivity and optimize the separation degree of the target spot and background interference.

[0027] As a preferred solution, in the step d of the step S2 of the method for rapid separation and detection of the fault diagnostic agent in the transformer insulating oil, the drying is performed at room temperature. After the development is completed, the thin layer plate is taken out and placed on a fume hood or a clean experimental table, and is naturally dried at room temperature (20-25°C) for 2-5 minutes until the solvent is completely volatilized and the spot is clearly visible; if the diagnostic agent itself has no fluorescence characteristics, the subsequent color developing step is needed; if the diagnostic agent contains a fluorescent group, the color developing step can be directly skipped.

[0028] As a preferred solution, in the step g of the step S2 of the method for rapid separation and detection of the fault diagnostic agent in the transformer insulating oil, the solvent is quickly removed by a hair dryer.

[0029] As a preferred solution, in the step a of the step S3 of the method for rapid separation and detection of the fault diagnostic agent in the transformer insulating oil, the flow rate is 0.5-1.0 mL / min. The flow rate balances the separation efficiency and the analysis time, and a too low flow rate can lead to a too long analysis period, and a too high flow rate can reduce the separation degree.

[0030] As a preferred solution, in the step a of the step S3 of the method for rapid separation and detection of the fault diagnostic agent in the transformer insulating oil, the column temperature is 25-30°C. The suitable temperature can optimize the interaction between the chiral stationary phase and the target, and avoid peak tailing or decomposition caused by high temperature.

[0031] As a preferred solution, in the step a of the step S3 of the method for rapid separation and detection of the fault diagnostic agent in the transformer insulating oil, the injection volume is 10-20 μL. The injection volume can ensure the detection signal intensity (signal-to-noise ratio ≥ 10) and avoid peak broadening caused by overload.

[0032] As a preferred solution, in the step a of the step S3 of the method for rapid separation and detection of the fault diagnostic agent in the transformer insulating oil, the mobile phase is a n-hexane-isopropyl alcohol system, and further preferably, the volume ratio of n-hexane to isopropyl alcohol is 75:25-99:1.

[0033] The detector is an ultraviolet-visible light detector (UV-Vis) or a fluorescence detector (FLD), and the optimal detection wavelength is set, and further preferably, the optimal detection wavelength is 365 nm or 254 nm. The wavelength is suitable for most diagnostic agents containing conjugated structures, such as benzene ring or carbonyl derivatives.

[0034] As a preferred solution, in the step b of the step S3 of the method for rapid separation and detection of the fault diagnostic agent in the transformer insulating oil, the second organic solvent is at least one of n-hexane and petroleum ether.

[0035] As a preferred solution, in the step c of the step S3 of the method for rapid separation and detection of the fault diagnostic agent in the transformer insulating oil, the content of the diagnostic agent in the insulating oil is quantitatively analyzed by an external standard method or an internal standard method. In the external standard method, a series of diagnostic agent standard solutions with known concentrations (such as 1 ppm, 5 ppm, 10 ppm, and 20 ppm) are prepared, injected into the HPLC system respectively to determine the peak area, and a standard curve (linear relationship between the peak area and the concentration) is drawn to back calculate the concentration according to the peak area of the sample to be detected. The external standard method is suitable for scenarios where the diagnostic agent standard is stable. In the internal standard method, an internal standard substance with similar properties to the diagnostic agent and without interference with the detection is added, and the concentration is calculated by the peak area ratio of the substance to be detected to the internal standard substance. The internal standard method can correct the injection error and instrument fluctuation, and improve the quantitative accuracy. In addition, by analyzing the peak area ratio of the enantiomers of the chiral diagnostic agent, the enantiomeric excess percentage (ee%=(peak area of the larger enantiomer-peak area of the smaller enantiomer) / (peak area of the larger enantiomer+peak area of the smaller enantiomer)×100%) can be further calculated to determine the degree of configuration change of the diagnostic agent in the fault process.

[0036] In the rapid separation and detection method of fault diagnostic agents in transformer insulating oil, the diether-type organic compound with a chiral center is at least one of 2,2'-bis(propoxy)-6,6'-dipropyl-1,1'-diphenyl, 2,2'-bis(nonoxy)-1,1'-binaphthyl, 2,2'-bis(propoxy)-1,1'-binaphthyl, 2,2'-bis(methoxy)-1,1'-binaphthyl, and 2,2'-bis(hexyloxy)-1,1'-binaphthyl. It contains two chiral carbon atoms, and the ether bond and benzene ring in its structure give it good solubility in insulating oil. The chiral center makes it easy to undergo configuration transformation (such as change in R / S configuration ratio) under the action of fault energy (such as high temperature / high energy electrons generated by partial discharge). Thus, early warning of faults can be achieved by the change in the chiral HPLC peak area ratio. The aforementioned diether organic compounds with chiral centers may be provided by Inokai (Tianjin) Biotechnology Co., Ltd., Beijing Bailingwei Technology Co., Ltd., or WuXi AppTec New Drug Development Co., Ltd.

[0037] The above-mentioned rapid separation and detection method for fault diagnostic agents in transformer insulating oil has a detection limit of 1 ppm for diether organic compounds with chiral centers.

[0038] According to a more specific embodiment of the present invention, the method for rapid separation and detection of fault diagnostic agents in transformer insulating oil includes:

[0039] S1. Sample pretreatment:

[0040] Take a sample of the insulating oil from the transformer to be tested, add an appropriate organic solvent to dilute it, and obtain the solution to be separated and purified;

[0041] S2. Rapid separation and purification using thin-layer chromatography (TLC):

[0042] a. Plate preparation: Use silica gel thin-layer chromatography plates;

[0043] b. Spotting: Use a micro sampler to spot the test solution obtained in step S1 onto a thin-layer plate;

[0044] c. Development: The spotted thin-layer plate is placed in a development tank and developed using an optimized developing solvent system. The developing solvent is one or a mixture of petroleum ether and ethyl acetate in a certain volume ratio.

[0045] d. Color development: After development, remove the thin-layer plate and let it air dry. If the diagnostic reagent itself is not fluorescent, select a suitable colorimetric reagent for color development; if the diagnostic reagent is fluorescent, observe it directly under a UV lamp.

[0046] e. Qualitative analysis: By calculating the Rf value of the target spot and comparing it with the standard, rapid qualitative identification of the diagnostic agent and its possible products and preliminary evaluation of the separation effect can be achieved;

[0047] f. Separation and purification: Scrape off the silica gel spot band containing the target standard, dissolve it in ethyl acetate, and obtain the standard solution by rapid filtration;

[0048] g. Concentration: The solvent is quickly removed by blowing with a hair dryer to obtain analytical grade standards;

[0049] S3. Precise quantitative detection by chiral high-performance liquid chromatography (HPLC):

[0050] a. Chromatographic conditions:

[0051] Chromatographic column: Chiral stationary phase column;

[0052] Mobile phase: n-hexane-isopropanol system;

[0053] Flow rate: 0.5-1.0 mL / min;

[0054] Column temperature: 25-30℃;

[0055] Detector: Select an ultraviolet-visible detector (UV-Vis) or a fluorescence detector (FLD) according to the properties of the diagnostic agent, and set the optimal detection wavelength;

[0056] Injection volume: 10-20 μL;

[0057] b. Sample analysis: The standard that has been treated and purified by S2 is dissolved in a suitable organic solvent to prepare the test solution, which is then injected into the high performance liquid chromatography system;

[0058] c. Quantitative analysis: The content of diagnostic agents in insulating oil is quantitatively analyzed by external standard method or internal standard method; the enantiomeric excess percentage is accurately calculated by the peak area ratio of chiral compounds.

[0059] Compared with the prior art, the present invention has the following beneficial technical effects:

[0060] 1. Highly efficient and fast, significantly improving fault response speed.

[0061] Thin-layer chromatography (TLC) is used for separation and purification, with a single sample development time of only 10-20 minutes (including spotting, development, and drying). Combined with multi-channel parallel spotting (e.g., 6-8 samples can be spotted simultaneously on one TLC plate), rapid separation and qualitative analysis of multiple samples can be completed within a few minutes. Compared to traditional column chromatography or direct HPLC analysis (where single sample pretreatment and detection typically take more than 1 hour), this significantly shortens the detection cycle, meeting the timeliness requirements for "early warning" of acute transformer faults and providing maintenance personnel with a valuable window for fault handling.

[0062] 2. High selectivity and high sensitivity, accurate identification of fault signals

[0063] In view of the characteristics of transformer insulating oil composition (containing base oil, antioxidant, aging product and other interferents), a chiral high performance liquid chromatography (Chiral HPLC) is adopted, and the enantiomer difference between the chiral diagnostic agent and its fault product is specifically recognized by the chiral stationary phase chromatographic column, which effectively overcomes the interference of complex matrix and realizes the accurate quantification of ppm level (1 mg / L). At the same time, combined with ultraviolet-visible detector (254 nm) or fluorescence detector (optimal emission wavelength matching diagnostic agent characteristic structure), the trace diagnostic agent can be distinguished from the background noise, the signal-to-noise ratio is greater than or equal to 10, and the quantification limit is as low as 3 ppm, which ensures the sensitive capture of early fault signals.

[0064] 3. Low cost, suitable for large-scale screening demand

[0065] The TLC process only needs silica gel thin layer plate, developing agent (cheap solvent such as petroleum ether / ethyl acetate) and conventional sample application tool, without expensive instruments and high-purity reagents, which is suitable for preliminary screening of large-scale samples (such as regular inspection of hundreds of transformers in power grid). After the background impurities of the sample are quickly screened out by TLC, only the diagnostic agent is further quantified by HPLC, which significantly reduces the overall analysis cost and improves the detection economy.

[0066] 4. Rich information, supporting comprehensive fault evaluation

[0067] The method creatively integrates the advantages of rapid and intuitive TLC and precise and specific chiral HPLC: TLC qualitatively identifies diagnostic agents and their possible products (such as configuration conversion intermediates) through the relative migration value (Rf value), and provides preliminary separation effect evaluation; chiral HPLC further provides accurate quantitative data and configuration change information through retention time, peak area and enantiomeric excess percentage. The combination of the two can not only determine whether there is abnormal diagnostic agent, but also quantify the abnormal degree and type, providing comprehensive data support for evaluating the transformer fault state (such as partial discharge, electric arc, overheating, etc.), and assisting the operation and maintenance personnel to accurately locate the fault risk.

[0068] 5. Strong specificity, filling the gap of new diagnostic agent detection technology

[0069] The present application is aimed at the particularity of chiral diagnostic agents (such as 2,2'-bis(propoxy)-6,6'-dipropyl-1,1'-diphenyl and other diether compounds) in transformer fault early warning scene, and solves the problem that such molecules are difficult to analyze due to serious background interference and low separation efficiency of traditional methods in complex insulating oil system. Especially, chiral HPLC can distinguish the enantiomer difference between the original configuration of the diagnostic agent and the fault conversion product, filling the gap of the detection technology of this new type of diagnostic agent.

[0070] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0071] Figure 1 This is a typical thin-layer chromatography (TLC) development diagram of the fault diagnosis agent and its characteristic products in Example 1;

[0072] Figure 2 This is the chromatogram of the enantiomers of the diagnostic reagent separated by chiral high-performance liquid chromatography (HPLC) in Example 1;

[0073] Figure 3 It is the integral area ratio of the enantiomeric separation of the diagnostic reagent using chiral high-performance liquid chromatography (HPLC) in Example 1;

[0074] Figure 4 This is the chromatogram of the limit of detection (LOQ) of the diagnostic reagent obtained by chiral high performance liquid chromatography (HPLC) in Example 1;

[0075] Figure 5 It is the integral area ratio of the enantiomers separated by the limit of quantitative detection (LOQ) of the diagnostic reagent using chiral high-performance liquid chromatography (HPLC) in Example 1. Detailed Implementation

[0076] The following description provides numerous specific details to offer a more thorough understanding of the technical solutions provided by this invention. However, it will be apparent to those skilled in the art that the technical solutions provided by this invention can be implemented without one or more of these details.

[0077] Example 1

[0078] This embodiment provides a method for rapid separation and detection of fault diagnostic agents in transformer insulating oil.

[0079] The diagnostic agent is 2,2'-bis(propoxy)-6,6'-dipropyl-1,1'-diphenyl (hereinafter referred to as diagnostic agent A), which is provided by Beijing Bailingwei Technology Co., Ltd.

[0080] 1. Sample pretreatment: Take 100 μL of transformer oil sample containing diagnostic reagent A, dilute with 50 μL of n-hexane to obtain the solution to be separated and purified.

[0081] 2. Rapid separation and purification by thin-layer chromatography (TLC): A 0.2 mm thick silica gel plate (5 cm × 20 cm) was used. The sample to be separated and purified was spotted onto one end of the plate using a micro-spotter. The plate was then placed in a developing tank, and petroleum ether was used as the developing solvent. After development, the plate was removed and allowed to air dry at room temperature. The separation results were observed under UV light. (See attached image for separation results.) Figure 3 By calculating the Rf value of the target spot and comparing it with the standard, rapid qualitative identification and preliminary separation effect assessment of the diagnostic reagent and its possible products can be achieved. The silica gel adsorption band containing the target standard is scraped off, dissolved in ethyl acetate, and rapidly filtered to obtain a solution of diagnostic reagent A. The solvent is then removed by blowing with a hairdryer, finally obtaining an analytical grade sample of diagnostic reagent A.

[0082] 3. Chiral HPLC quantification:

[0083] Column: Chiralpak IC (4.6x250mm, 5μm);

[0084] Mobile phase: n-hexane:isopropanol = 99:1 (v / v);

[0085] Flow rate: 0.5 mL / min;

[0086] Detector: UV 254nm;

[0087] Column temperature: 30℃;

[0088] Injection volume: 10 μL.

[0089] The standard, processed and purified in step 2, was dissolved in n-hexane to prepare the test solution, which was then injected into a high-performance liquid chromatography (HPLC) system. The content of the diagnostic reagent in the insulating oil was quantitatively analyzed; the enantiomeric excess percentage was accurately calculated using the peak area ratio of chiral compounds. Results: ( R The retention time of the configurational diagnostic agent was 7.32 min. S The configuration retention time was 8.17 min, and baseline separation was achieved. The enantiomeric excess percentage can be obtained by integrating the area ratio.

[0090] The limit of detection (LOQ) is the lowest concentration that can be quantitatively determined by this method under acceptable precision and accuracy requirements. It is typically defined as the concentration at which the signal-to-noise ratio (S / N) is 10:1.

[0091] With diagnostic agent A as a standard sample, 1 mL of n-hexane solution with a concentration of 1 mg / mL, 0.1 mg / mL and 0.01 mg / mL was prepared respectively. 10 μL of the above solution was injected for chiral HPLC analysis respectively. The results showed that the quantitative detection limit (LOQ) of the method for diagnostic agent A was 1 x 10 -3 mg / mL (i.e. 1 ppm).

[0092] Figure 1 is a typical thin layer chromatography (TLC) development effect diagram of the fault diagnostic agent and its characteristic products in Example 1. From the figure, it can be seen that the spots are clearly separated, indicating that the operation of this TLC experiment is relatively successful, and the thin layer chromatography analysis method used is effective for detecting the fault diagnostic agent and its by-products in oil, which can provide basic information for further analysis.

[0093] Figure 2 is a chromatogram of chiral high performance liquid chromatography (HPLC) separation of diagnostic agent enantiomers in Example 1. Figure 2 Two well-separated chromatographic peaks appear in the middle, corresponding to two enantiomers (R-type and S-type) of the diagnostic agent, Figure 2 clearly showing the separation effect of the enantiomers, indicating that the selected chiral chromatographic conditions can effectively distinguish the two enantiomers, and the sample purity is high.

[0094] Figure 3 is the integral area ratio of chiral high performance liquid chromatography (HPLC) separation of diagnostic agent enantiomers in Example 1. From the figure, Figure 3It can be seen that: 1. Peak number and retention time: Peak 1 has a retention time of 7.327 minutes, and Peak 2 has a retention time of 8.171 minutes. The retention times reflect the retention behavior of different enantiomers on the chromatographic column. The different retention times of Peak 1 and Peak 2 indicate that the two enantiomers are well separated on the chromatographic column and can be effectively distinguished; 2. Integral area: Peak 1 has an area of 6636483, Peak 2 has an area of 6761160, and the total area is 13397643. The integral area is usually related to the content of the component in enantiomer separation (assuming the same detection response factor). The areas of Peak 1 and Peak 2 are relatively close, indicating that the contents of the two enantiomers in the sample are roughly equivalent; 3. Peak height: Peak 1 has a height of 449945, Peak 2 has a height of 390789, and the total height is 840734. Peak height can also reflect the content of the component. The height of Peak 1 is slightly higher than that of Peak 2, which is consistent with the area reflection, i.e., the contents of the two enantiomers are similar, but the content of Peak 1 is slightly higher; 4. Concentration: Peak 1 has a concentration of 49.535%, and Peak 2 has a concentration of 50.465%. The concentration data further supports the conclusion that the contents of the two enantiomers are similar. The concentration of Peak 2 is slightly higher than that of Peak 1, which is slightly different from the results of area and peak height, which may be due to the slight difference in detection response factor or calculation method, but overall the concentrations of the two enantiomers are very close. It can be seen that: the two enantiomers are well separated on the chromatographic column because their retention times are significantly different; the contents of the two enantiomers in the sample are roughly equivalent, as shown by the integral area, peak height, and concentration.

[0095] Figure 4 is the chromatogram of the diagnostic agent quantitative limit of detection (LOQ) in Example 1 using chiral high-performance liquid chromatography (HPLC). It is obtained by Figure 4 It can be seen that: 1. The number and position of the chromatographic peaks: there are two main chromatographic peaks in the figure, which appear at about 7.467 min and 8.33 min. This indicates that there are two components in the sample that can be detected. Before these two main peaks, there is a relatively stable baseline without obvious interference peaks, indicating that there is less interference from the matrix or impurities in this retention time range; 2. Separation degree and symmetry: as can be seen from the figure, the separation degree between the two main peaks looks good, and the peak shape is also relatively symmetrical (without obvious tailing or front stretching). This means that under the conditions of chiral HPLC, the two components are effectively separated, which is conducive to accurate quantification. It can be seen that the two components can be effectively separated, detected, and have good peak shape and stable baseline, indicating that this method can achieve accurate quantification of the diagnostic agent at this concentration level.

[0096] Figure 5 is the integral area ratio of enantiomer separation of the diagnostic agent quantitative limit of detection (LOQ) in Example 1 using chiral high-performance liquid chromatography (HPLC). It is obtained by Figure 5It can be seen that the two enantiomers have different retention times, indicating that the chiral HPLC method successfully realizes the separation of the two, which is crucial for accurately determining the content of each enantiomer. Moreover, from the comparison of peak area, peak height and concentration, there is a certain difference in the content of the two enantiomers, but the difference is not particularly large, indicating that the method has certain accuracy and reliability in quantitative detection of enantiomers, and can distinguish and determine the content of the two enantiomers which are relatively close.

[0097] The above only is the preferred embodiment of the present application, and is not used to limit the present application, for the person skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for rapid separation and detection of fault diagnostic agents in transformer insulating oil, characterized in that, The rapid separation and detection method includes: S1. Sample pretreatment: Take a sample of the transformer insulating oil to be tested, add the first organic solvent for dilution, and obtain the test solution to be separated and purified; S2. Rapid separation and purification by thin-layer chromatography: a. Making plates; b. Spotting; c. Expand; d. Color development: After development, air dry; if the diagnostic reagent itself is non-fluorescent, use a colorimetric reagent for color development; if the diagnostic reagent is fluorescent, observe directly under a UV lamp. e. Qualitative analysis: By calculating the specific shift value of the target spot and comparing it with the standard, rapid qualitative identification and preliminary evaluation of the separation effect of the diagnostic agent and its products can be achieved; f. Separation and purification: Scrape off the silica gel spot band containing the target standard, dissolve it in ethyl acetate, and obtain the standard solution by suction filtration; g. Concentration: Remove the solvent to obtain analytical grade standards; S3. Precise quantitative detection by chiral high-performance liquid chromatography: a. Chromatographic conditions: Chromatographic column: Chiral stationary phase column; b. Sample analysis: The standard that has been treated and purified by S2 is dissolved in a second organic solvent to prepare the test solution, which is then injected into the high performance liquid chromatography system; c. Quantitative analysis: Quantitative analysis of the content of diagnostic agents in insulating oil; quantitative calculation of enantiomeric excess percentage by peak area ratio of chiral compounds; The fault diagnosis agent is a diether organic compound with a chiral center; In step S1, the first organic solvent is at least one of n-hexane and petroleum ether; In step S3a: flow rate: 0.5-1.0 mL / min; column temperature: 25-30℃; injection volume: 10-20 μL; In step S3b: the second organic solvent is at least one of n-hexane and petroleum ether.

2. The rapid separation and detection method for fault diagnostic agents in transformer insulating oil according to claim 1, characterized in that, In step S2a, a silica gel thin-layer chromatography plate is used for plate preparation. In step S2b, the test liquid obtained in step S1 is spotted onto a thin-layer plate. In step S2c, the spotted thin-layer plate is placed in a developing tank for development. In step S2c, the developing solvent used is one or both of petroleum ether and ethyl acetate; In step S2, step d, the product is air-dried at room temperature. In step S2, step g involves using a hair dryer to quickly remove the solvent.

3. The rapid separation and detection method for fault diagnostic agents in transformer insulating oil according to claim 1, characterized in that, In step S3a: Mobile phase: n-hexane-isopropanol system; Detector: Ultraviolet-visible detector or fluorescence detector, and set the optimal detection wavelength.

4. The rapid separation and detection method for fault diagnostic agents in transformer insulating oil according to claim 3, characterized in that, In the mobile phase, the volume ratio of n-hexane to isopropanol is 75:25-99:1; The optimal detection wavelength is 365nm or 254nm.

5. The rapid separation and detection method for fault diagnostic agents in transformer insulating oil according to claim 1, characterized in that, In step S3c, the content of diagnostic agent in insulating oil is quantitatively analyzed by external standard method or internal standard method.

6. The rapid separation and detection method for fault diagnostic agents in transformer insulating oil according to claim 1, characterized in that, The diether organic compound having a chiral center is at least one of 2,2'-bis(propoxy)-6,6'-dipropyl-1,1'-diphenyl, 2,2'-bis(nonoxy)-1,1'-binaphthyl, 2,2'-bis(propoxy)-1,1'-binaphthyl, 2,2'-bis(methoxy)-1,1'-binaphthyl, and 2,2'-bis(hexyloxy)-1,1'-binaphthyl.

7. The rapid separation and detection method for fault diagnostic agents in transformer insulating oil according to claim 1, characterized in that, The rapid separation and detection method has a detection limit of 1 ppm for diether organic compounds with chiral centers.

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