Method for detecting content of methylal in gasoline

Abstract

The invention relates to a method for detecting the content of methylal in gasoline, which comprises the following steps: establishing a detection system, setting detection parameters and a chromatographic separation program, determining the qualitative retention time of methylal and a quantitative correction curve graph, detecting the content of methylal in gasoline and the like. The detection system comprises a nitrogen source, a hydrogen source, a compressed air source, a corresponding flowmeter, a sample injector, a detailed hydrocarbon analyzer with a vaporizing chamber, a capillary chromatographic column and a detector, a computer workstation with chromatographic data processing software and the like. The method is creative application of the DHA technology in gasoline methylal detection, and is used for detecting gasoline with the methylal content of less than or equal to 2.0% by mass or gasoline with the methylal content of less than or equal to 2.0% by mass after being diluted by methylal-free gasoline, the quantitative calibration curve of the method has excellent linearity, the detection sensitivity is high, the accuracy is good, and the method is suitable for industrial production. The problems of convenience and economy during application are practically solved, and the method can be widely applied to supervision and quality control of blended gasoline.

Description

Technical Field

[0001] This invention relates to a method for detecting the content of methyl acetal, and more particularly to a method for detecting the content of methyl acetal in gasoline, belonging to the technical field of gasoline quality testing methods. Background Technology

[0002] Methylal, with the chemical formula CH3(OCH3)2, also known as dimethoxymethane, is a colorless, clear, volatile, and flammable liquid. Currently priced at approximately 3500 RMB / ton, it possesses excellent solubility, a low boiling point (around 42℃), and good water miscibility. These characteristics have led to its widespread application in various industrial sectors, such as in insecticide formulations, leather and automotive polishes, and air fresheners. Furthermore, due to its excellent degreasing and volatility, methylal can also be used as a cleaning agent, replacing Freon (F11 and F13) and other chlorinated solvents. This makes it an environmentally friendly product that can reduce volatile organic compound (VOC) emissions and lower air pollution levels.

[0003] Methyl tert-butyl ether (chemical formula C5H12O, abbreviated as MTBE) is a legal gasoline additive. It has a moderate oxygen content, a high octane rating, and is slightly soluble in water. It can improve combustion performance and reduce exhaust pollution, so it is currently a very good gasoline additive and is widely used. However, its price is relatively high, usually around 6,800 yuan / ton. Methyl acetal, on the other hand, is not a legal gasoline additive. As early as 2011, PetroChina had explicitly stipulated that gasoline purchased from external sources must not contain methyl acetal. However, because the price of methyl acetal is much lower than that of methyl tert-butyl ether, some companies often resort to deceptive means to illegally add methyl acetal to gasoline in order to earn a high price difference and reduce their product costs.

[0004] Long-term use of blended gasoline containing methyl acetal can cause serious and multifaceted damage to automobiles.

[0005] First, methyl acetal can damage a car's three-way catalytic converter, leading to excessive emissions and environmental pollution. Second, methyl acetal is corrosive to car engines and emission systems, shortening engine life, increasing maintenance costs, and clogging fuel lines and injectors during combustion, producing deposits and causing gum and carbon buildup in intake valves and cylinders. This directly affects the normal operation of gasoline engines, resulting in insufficient power, increased fuel consumption, and in severe cases, vehicle breakdown. Besides vehicle damage, blended gasoline containing methyl acetal poses a serious threat to human health. Long-term exposure to blended gasoline containing methyl acetal and other components can lead to chronic poisoning, manifesting as gradual damage to the respiratory and central nervous systems. Short-term symptoms include dizziness and nausea, while long-term exposure may lead to cancer. Furthermore, methyl acetal has a swelling effect on rubber, causing seals and fuel lines to fail, leading to oil leaks and potentially fires. Adding methyl acetal also emulsifies gasoline, compromising fuel quality and stability.

[0006] Although methyl acetal itself is considered environmentally friendly as a solvent, when it is added to gasoline and burned in the engine, it produces harmful byproducts that cause environmental pollution. At the same time, because methyl acetal can damage the three-way catalytic converter of a car, it increases the emission of harmful gases from the vehicle and exacerbates air pollution. Therefore, the addition of methyl acetal to gasoline must be strictly controlled.

[0007] In the existing technology, the main methods for detecting methyl acetal in gasoline include infrared spectroscopy, gas chromatography, and their combined techniques.

[0008] Infrared spectroscopy is a commonly used method for substance detection and analysis, but it shows obvious limitations when detecting methyl acetal in gasoline. This is because the method is affected by other components in gasoline, leading to inaccurate detection results. In particular, for low concentrations of methyl acetal, its characteristic absorption peak may be masked by the absorption peaks of other components, making it difficult to detect accurately.

[0009] In addition, infrared spectroscopy requires specialized instruments and personnel, and the operation process is relatively complex, making it unsuitable for non-professionals. Furthermore, the debugging and maintenance of these instruments also require professional technical support, which greatly increases the cost and time of detection. Therefore, it limits its application in rapid on-site detection.

[0010] Gas chromatography is another method for detecting methylal, but conventional gas chromatography requires complex sample pretreatment, such as desorption and purification, which increases the complexity and difficulty of the operation. These pretreatment steps are not only time-consuming and labor-intensive, but may also introduce errors or cause sample contamination, affecting the accuracy of the detection results. In addition, when dealing with complex samples, conventional gas chromatography requires a long time for separation and detection. For complex mixtures such as gasoline, the methylal peak may overlap with other hydrocarbon component peaks, making it difficult to accurately identify and quantify. Even with pretreatment, good separation and accurate test results may not be achieved.

[0011] Besides the two existing methods mentioned above, there are other analytical techniques available for the detection of methylal, such as mass spectrometry or chromatography-mass spectrometry. While these methods offer higher accuracy and sensitivity, they typically require more expensive equipment and more skilled operators, and therefore are not suitable for large-scale deployment or rapid on-site detection.

[0012] Detailed Hydrocarbon Analysis (DHA) is a technique based on gas chromatography (GC) or gas chromatography-mass spectrometry (GC-MS) used to accurately separate, qualitatively and quantitatively analyze various hydrocarbon components (from C4 to C12 and above) in petroleum products. It can detect not only group compositions (alkanes, isoalkanes, alkenes, cycloalkanes, and aromatics) but also identify and quantify individual hydrocarbons. Its core technology is to use the high separation efficiency of chromatographic columns to separate complex hydrocarbon mixtures and perform qualitative and quantitative analysis using detectors.

[0013] DHA technology combines data from detailed hydrocarbon pre-analysis (DHA) with high-temperature simulated distillation results. Predefined settings for each sample type facilitate reliable peak identification. The DHA detailed hydrocarbon analyzer is compatible with major chromatographic data systems and can provide low detection limits, a wide dynamic linear range, and features low interference, high analytical accuracy, and fast analysis speed.

[0014] However, since gasoline is a complex mixture containing hundreds of different hydrocarbon compounds, the physicochemical properties of which are similar to those of methyl acetal. Therefore, applying DHA technology to the detection of methyl acetal in gasoline faces many challenges. This is because methyl acetal is difficult to separate from gasoline components in a non-polar capillary column. Currently, there is no accurate, reliable, standardized, and regulated technology for the detection of methyl acetal in gasoline using DHA technology. Summary of the Invention

[0015] To overcome the shortcomings of existing technologies and fully realize the application potential of DHA technology, this invention, through pioneering optimization and verification, solves the problem of separating methylal from gasoline components. Based on this, it establishes a precise qualitative and quantitative method for methylal in gasoline, making DHA technology an effective and practically applicable technique for detecting methylal in gasoline. This effectively solves the problems of convenience and economy in practical applications, and can be widely used in the market supervision and quality control of blended gasoline, effectively curbing the illegal addition of methylal to gasoline, thereby protecting consumer rights and environmental safety. The specific technical solution is as follows:

[0016] A method for detecting the methylal content in gasoline, used to detect the mass percentage of methylal in gasoline, wherein the mass percentage of methylal in the gasoline should be ≤2.0%, or the mass percentage of methylal in the gasoline after dilution with methylal-free gasoline should be ≤2.0%, and the detection process includes the following steps:

[0017] The steps for setting up the detection system, configuring detection parameters and chromatographic separation procedures, determining the qualitative retention time and quantitative calibration curve for methyl acetal, and detecting the methyl acetal content in gasoline, including:

[0018] The detection system includes a nitrogen source, a hydrogen source, a compressed air source, a nitrogen flow meter, a hydrogen flow meter, a compressed air flow meter, an injector, a detailed hydrocarbon analyzer with a vaporization chamber, a capillary chromatographic column and a detector, and a computer workstation with chromatographic data processing software.

[0019] The steps for assembling the detection system include:

[0020] Connect the nitrogen source, hydrogen source, and compressed air source to the nitrogen flow meter, hydrogen flow meter, and compressed air flow meter respectively using pipes. Then connect the output end of the nitrogen flow meter to the vaporization chamber of the detailed hydrocarbon analyzer. Connect the output ends of the hydrogen flow meter and compressed air flow meter to the detector of the detailed hydrocarbon analyzer. Connect the injector to the vaporization chamber. Connect the capillary chromatographic column between the vaporization chamber and the detector. Finally, connect the signal line of the detector to the computer workstation.

[0021] The steps for setting the detection parameters and chromatographic separation program include:

[0022] The temperature inside the injection port of the injector is set to 250°C, the injection volume of the injector is set to 0.1 μL, the split ratio of the vaporization chamber is set to 150:1, the temperature of the detector is set to 250°C, the flow rates of the hydrogen flow meter and the compressed air flow meter are set to 30 ml / min, the flow rate of the nitrogen flow meter is set to 20 ml / min, the temperature control program of the column oven of the detailed hydrocarbon analyzer is set to the column oven gradient temperature control program, and the set column oven gradient temperature control program is input into the controller of the detailed hydrocarbon analyzer.

[0023] The steps for determining the qualitative retention time and quantitative calibration curve of methyl acetal include:

[0024] Using gasoline without methyl acetal as a solvent, methyl acetal standards were prepared into standard methyl acetal gasoline solutions with a mass percentage in the range of 0 to 2.0% and containing at least four different concentration gradients of 0 and 2.0%. Each of the standard methyl acetal gasoline solutions was then placed in a cool environment for refrigeration.

[0025] The detection system is turned on, and standard methyl acetal gasoline solutions with different methyl acetal concentrations that have completed the refrigeration process are injected one by one into the detailed hydrocarbon analyzer through the injector. The detailed hydrocarbon analyzer performs gas chromatography separation and detection on the standard methyl acetal gasoline solutions one by one according to the input column oven gradient temperature control program. Finally, gas chromatograms of standard methyl acetal gasoline solutions with different methyl acetal concentrations are obtained from the computer workstation.

[0026] By analyzing the gas chromatograms of the standard methyl acetal gasoline solutions with different methyl acetal concentrations, the retention time of the methyl acetal peak in the gas chromatogram was determined and defined as the qualitative retention time of the methyl acetal contained in the gasoline.

[0027] The methyl acetal mass percentage was determined by the peak area of ​​methyl acetal in the gas chromatogram of standard methyl acetal gasoline solutions with different concentrations of methyl acetal. The methyl acetal peak area corresponding to different methyl acetal mass percentages after passing the recovery test was used to establish a methyl acetal peak area-mass percentage content calibration curve in gasoline using the three-point standard addition method. This curve was defined as the quantitative calibration curve of methyl acetal mass percentage in gasoline.

[0028] The detection steps for the methyl acetal content in the gasoline include:

[0029] The gasoline sample to be tested is sealed and placed in the same refrigeration environment as the standard methylal gasoline solution for the same duration. The mass percentage of methylal in the gasoline sample should be ≤2.0%, or the mass percentage of methylal in the gasoline sample after dilution with methylal-free gasoline should be ≤2.0%.

[0030] Take out the gasoline sample that has completed the refrigeration process and place it in the chromatographic vial that is matched with the injector. Start the detection system and let the injector inject the gasoline sample into the detailed hydrocarbon analyzer for detection. The detailed hydrocarbon analyzer controls the column oven temperature according to the input column oven gradient temperature control program until the detection is completed. Then, the corresponding gas chromatogram of the gasoline sample is obtained through the computer workstation.

[0031] The peak in the gas chromatogram of the gasoline sample that matches the qualitative retention time of methyl acetal is identified as the methyl acetal peak of the gasoline sample. The corresponding methyl acetal mass percentage value is obtained from the quantitative calibration curve based on the area value of this methyl acetal peak, thus completing the detection of the methyl acetal content of the gasoline sample.

[0032] Furthermore, the detailed column oven gradient temperature control program of the hydrocarbon analyzer is as follows:

[0033] The initial temperature of the column oven is set to 5℃. After holding it for 10 minutes, the temperature is increased to 50℃ at a rate of 5℃ / minute. It is then held for 50 minutes. Next, the temperature is increased to 200℃ at a rate of 1.5℃ / minute. After holding it for 5 minutes, the temperature is increased to 250℃. This temperature is then maintained until the test is completed.

[0034] Preferably, the refrigeration environment is a cool, dark environment at 5°C, and the refrigeration time is 30 minutes.

[0035] Furthermore, the standard for passing the recovery rate test is a recovery rate of 95% to 105%.

[0036] Preferably, the detailed hydrocarbon analyzer is an Agilent 7890 Series II GC, and the injector is an Agilent automated liquid sampler.

[0037] Preferably, the detailed hydrocarbon analyzer uses a dimethyl silica capillary column.

[0038] Furthermore, after the dimethyl silica capillary column has separated a set of samples, it is washed with 95% ethanol or anhydrous ethanol of analytical grade or higher.

[0039] Furthermore, the detector of the detailed hydrocarbon analyzer is a hydrogen flame ionization detector.

[0040] Preferably, the chromatographic data processing software is the Chemstation chemical analysis software system.

[0041] Further:

[0042] The detection system also includes a nitrogen purifier, a hydrogen purifier, and an air purifier;

[0043] The nitrogen purifier, the hydrogen purifier, and the air purifier are each connected at both ends to the corresponding nitrogen source, hydrogen source, and compressed air source, as well as the nitrogen flow meter, the hydrogen flow meter, and the compressed air flow meter. Compared with the prior art, the present invention has the following outstanding beneficial effects and significant progress:

[0044] 1) The method for detecting methyl acetal content in gasoline provided by this invention is a creative application of DHA technology in the detection of methyl acetal in gasoline. Experiments have shown that this detection method, when used to detect gasoline containing methyl acetal at a mass percentage of ≤2.0%, or gasoline containing methyl acetal at a mass percentage of ≤2.0% after dilution with methyl acetal-free gasoline, exhibits excellent linearity in its quantitative calibration curve, high detection sensitivity, and good accuracy. It can fully utilize the application potential of DHA technology, making it an effective and practical technical means for detecting methyl acetal in gasoline. It effectively solves the problems of convenience and economy in practical applications and can be widely used in the market supervision and quality control of blended gasoline, effectively curbing the illegal addition of methyl acetal to gasoline, thereby protecting the rights and interests of consumers and environmental safety.

[0045] 2) This invention establishes a system and method for detecting methyl acetal content in gasoline through steps such as the construction of a detection system, setting detection parameters and chromatographic separation procedures, determining the qualitative retention time and quantitative calibration curve of methyl acetal, and detecting the methyl acetal content in gasoline. It utilizes detection instruments and auxiliary equipment such as nitrogen source, hydrogen source, compressed air source, nitrogen flow meter, hydrogen flow meter, compressed air flow meter, injector, detailed hydrocarbon analyzer with vaporization chamber, capillary chromatographic column and detector, and computer workstation with chromatographic data processing software. This system and method are simple, convenient, practical and reliable.

[0046] 3) The detection method provided by this invention has an injection port temperature of 250℃, an injection volume of 0.1 μL, a split ratio of 150:1, a detector temperature of 250℃, a hydrogen and compressed air flow rate of 30 ml / min, a nitrogen flow rate of 20 ml / min, and a column oven temperature of a detailed hydrocarbon analyzer with gradient temperature control. During detection, a gas chromatogram is first obtained using a standard methylal gasoline solution to determine the peak retention time and peak area of ​​methylal in gasoline. This peak retention time is defined as the qualitative retention time of methylal in gasoline. The peak area values ​​of methylal corresponding to different methylal mass percentages after passing the recovery rate test are used to establish a calibration curve of the methylal mass percentage in gasoline using the three-point standard addition method. This serves as the quantitative calibration curve of the methylal mass percentage in gasoline, thereby detecting the methylal content in gasoline. These detection parameters and method steps are novel and unique, ensuring satisfactory detection results.

[0047] 4) The detection method provided by this invention includes a process of refrigerating the standard solution and the sample to be tested in a cool, dark environment at 5°C for 30 minutes. Experiments have shown that the refrigeration process effectively eliminates the influence of ambient temperature on the volatilization of light hydrocarbon components in the sample, ensuring that all light hydrocarbon components in the sample, except for methane, are in a low-temperature liquefied state before vaporization separation. This effectively protects the light and volatile components in the sample and ensures the integrity of the sample. At the same time, the designed column oven gradient temperature control program keeps the sample and the initial test temperature of the chromatographic column set at 5°C synchronized, achieving effective cold trap focusing, thereby ensuring high resolution, high sensitivity, and high accuracy of the analytical results.

[0048] 5) In the detection method provided by this invention, the temperature inside the injection port is set to 250°C. This temperature setting not only ensures that all components in the sample can be completely vaporized instantly and smoothly enter the capillary column for chromatographic separation, but more importantly, it can avoid thermal decomposition of the components in the sample, which would affect the test results. In addition, setting the temperature inside the injection port to 250°C ensures that the sample can flow smoothly through the entire flow path, including the injection port and the chromatographic column, without causing some high-boiling-point components to condense due to a temperature drop at a certain point in the transmission line, which would result in loss and peak tailing. It also ensures temperature matching with the subsequent detection components, thereby further ensuring the best separation and detection effect of methyl acetal.

[0049] 6) In the detection method provided by the present invention, a split ratio of 150:1 is set. This split ratio ensures that the relevant components in the sample are not lost and that each component in the sample is effectively separated, thereby obtaining a clear and complete gas chromatogram containing each component and ensuring the accuracy of the detection.

[0050] 7) The detection method provided by this invention controls the temperature of the column oven, i.e., the capillary column, through a gradient temperature control program. The initial test temperature is set to 5°C, synchronized with the refrigeration temperature of the sample, to achieve effective cold trap focusing, i.e., allowing low-boiling-point substances to focus at the column head. The subsequent gradient uniform temperature increase not only allows the capillary column to uniformly reach the set separation and detection temperature, but also allows the medium-boiling-point components in the sample to elute and separate at a faster rate, saving separation time and ensuring consistent separation and detection conditions, thereby guaranteeing the separation effect. In the final stage, the column oven temperature reaches 250°C, which ensures that all high-boiling-point substances in the sample are separated and washed out, ensuring not only the cleanliness of the chromatographic column, but also consistency with the detector's detection temperature, making the detection smoother and the detection data more accurate.

[0051] In summary, the technical solution provided by this invention overcomes the shortcomings of the prior art, can effectively and accurately detect the content of methyl acetal in gasoline, and is simple, convenient, reliable and practical compared with the prior art. Therefore, it has outstanding beneficial effects and significant progress, and is of great promotion and application value. Attached Figure Description

[0052] To more clearly illustrate the technical solution of the present invention and the technical effects of implementing the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly introduced below.

[0053] Obviously, the accompanying drawings described below are only some of the drawings in the embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort, but these other drawings also belong to the drawings required for the embodiments of the present invention, wherein:

[0054] Figure 1 This is a schematic diagram of the structure of the gasoline methyl acetal content detection system provided in an embodiment of the present invention;

[0055] Figure 2 Gas chromatogram of a standard methyl acetal gasoline solution with a mass percentage of 0.5% provided in this invention example;

[0056] Figure 3 Gas chromatogram of a standard methyl acetal gasoline solution with a mass percentage of 1.0% provided in this invention example;

[0057] Figure 4 Gas chromatogram of a standard methyl acetal gasoline solution with a mass percentage of 2.0% provided in this invention example;

[0058] Figure 5A calibration curve of methyl acetal peak area versus mass percentage content of a standard methyl acetal gasoline solution provided for the present invention.

[0059] Figure 6 The graph shows the test results of the methyl acetal content of each gasoline sample in the 0.5% methyl acetal group provided as an example of the present invention.

[0060] Figure 7 The graph shows the test results of the methyl acetal content of each gasoline sample in the methyl acetal group with a mass percentage concentration of 1.0% provided for the present invention.

[0061] Figure 8 The graph shows the test results of the methyl acetal content of each gasoline sample in the methyl acetal group with a mass percentage concentration of 2.0% provided for the present invention.

[0062] Figure 9 The infrared spectroscopy content correction curve of the methyl acetal gasoline standard solution provided as a comparative example of the present invention is shown.

[0063] In the picture:

[0064] 11-Nitrogen source, 12-Hydrogen source, 13-Compressed air source, 21-Nitrogen flow meter, 22-Hydrogen flow meter, 23-Compressed air flow meter, 30-Injector, 40-Detailed hydrocarbon analyzer, 41-Vaporization chamber, 42-Capillary chromatographic column, 43-Detector, 50-Computer workstation, 61-Nitrogen purifier, 62-Hydrogen purifier, 63-Air purifier. Detailed Implementation

[0065] To make the technical solution, beneficial effects and significant progress of the present invention clearer and more comprehensive, the technical solution provided by the present invention will be clearly and completely described below through specific embodiments and comparative examples. Obviously, the embodiments and comparative examples described below are only some embodiments and comparative examples of the present invention, and not all of them.

[0066] Based on the embodiments and comparative examples provided by this invention, all other embodiments and comparative examples obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0067] It should be noted that:

[0068] The terms "firstly," "secondly," etc., used in the claims, description, and examples and comparative cases of this invention are merely for distinguishing different objects and not for describing a specific order; furthermore, the term "comprising" and any variations thereof are intended to cover non-exclusive inclusion, for example, including not only a series of listed steps or units of processes, methods, systems, products, or devices, but also optionally steps or units not listed, or optionally other operational steps or units inherent to these processes, methods, products, or devices.

[0069] It should be understood that some basic operational terms commonly used in the art are used in the description of the embodiments of the present invention, such as "injection" and "separation". These terms should be interpreted broadly, that is, they can refer to conventional operations performed using various conventional equipment and instruments in the art, or they can refer to operations performed using the latest equipment, such as programmed operations and unmanned automatic operations. Unless otherwise explicitly limited, those skilled in the art should understand the specific meaning of the above terms in the present invention according to the specific circumstances and adopt specific operating methods to achieve their operational objectives.

[0070] It should also be noted that:

[0071] The following specific embodiments can be combined with each other. The same or similar concepts or processes may be repeated in the implementation cases and comparative examples. In addition, all kinds of instruments, equipment, gases, reagents and standards involved in the following specific embodiments are commercially available unless otherwise specified.

[0072] The technical solution of the present invention will now be described in detail with reference to specific embodiments. Example

[0073] This embodiment provides a method for detecting the mass percentage of methyl acetal in gasoline, wherein the mass percentage of methyl acetal in the gasoline to be tested should be ≤2.0%, or the mass percentage of methyl acetal in the gasoline to be tested after dilution with methyl acetal-free gasoline should be ≤2.0%. The specific detection method includes the following steps:

[0074] The steps for setting up the detection system, configuring detection parameters and chromatographic separation procedures, determining the qualitative retention time and quantitative calibration curve for methyl acetal, and detecting the methyl acetal content in gasoline, including:

[0075] like Figure 1The schematic diagram of the gasoline methyl acetal content detection system provided in this embodiment of the invention shows that the detection system includes a nitrogen source 11, a hydrogen source 12, a compressed air source 13, a nitrogen flow meter 21, a hydrogen flow meter 22, a compressed air flow meter 23, an injector 30, a detailed hydrocarbon analyzer 40 with a vaporization chamber 41, a capillary chromatographic column 42 and a detector 43, and a computer workstation 50 with chromatographic data processing software.

[0076] like Figure 1 As shown, the steps for assembling the above detection system include:

[0077] Connect nitrogen source 11, hydrogen source 12, and compressed air source 13 to nitrogen flow meter 21, hydrogen flow meter 22, and compressed air flow meter 23 respectively via pipes. Then connect the output end of nitrogen flow meter 21 to vaporization chamber 41 of detailed hydrocarbon analyzer 40. Connect the output ends of hydrogen flow meter 22 and compressed air flow meter 23 to detector 43 of detailed hydrocarbon analyzer 40. Connect injector 30 to vaporization chamber 41. Connect capillary column 42 between vaporization chamber 41 and detector 43. Finally, connect the signal line of detector 43 to computer workstation 50.

[0078] Furthermore, such as Figure 1 As shown, the optimized detection system also includes:

[0079] The nitrogen purifier 61, hydrogen purifier 62, and air purifier 63 are provided, wherein each of the nitrogen purifier 61, hydrogen purifier 62, and air purifier 63 is connected at both ends to the corresponding nitrogen source 11, hydrogen source 12, compressed air source 13, nitrogen flow meter 21, hydrogen flow meter 22, and compressed air flow meter 23, respectively.

[0080] The steps for setting the detection parameters and chromatographic separation program include:

[0081] The temperature inside the injection port of the injector 30 is set to 250℃, the injection volume of the injector 30 is set to 0.1 μL per injection, the split ratio of the vaporization chamber 41 is set to 150:1, the temperature of the detector 43 is set to 250℃, the flow rates of the hydrogen flow meter 22 and the compressed air flow meter 23 are set to 30 ml / min, the flow rate of the nitrogen flow meter 21 is set to 20 ml / min, the temperature control program of the column oven of the detailed hydrocarbon analyzer 40 is set to the column oven gradient temperature control program, and the set column oven gradient temperature control program is input into the controller of the detailed hydrocarbon analyzer 40, wherein:

[0082] The detailed column oven gradient temperature control program of the hydrocarbon analyzer 40 is as follows: the initial temperature of the column oven is set to 5℃, held for 10 minutes, then increased to 50℃ at a rate of 5℃ / minute, held for 50 minutes, then increased to 200℃ at a rate of 1.5℃ / minute, held for 5 minutes, then increased to 250℃, and then held at this temperature until the detection is completed.

[0083] The steps for determining the qualitative retention time and quantitative calibration curve of methyl acetal include:

[0084] Using gasoline without methyl acetal as a solvent, methyl acetal standards were prepared into standard methyl acetal gasoline solutions with a mass percentage in the range of 0 to 2.0% and containing at least four different concentration gradients of 0 and 2.0%. Each standard methyl acetal gasoline solution was then placed in a cool environment for refrigeration.

[0085] The detection system is turned on, and standard methyl acetal gasoline solutions with different methyl acetal concentrations that have completed the refrigeration process are injected one by one into the detailed hydrocarbon analyzer 40 through the injector 30. The detailed hydrocarbon analyzer 40 then performs gas chromatography separation and detection on the standard methyl acetal gasoline solutions one by one according to the input column oven gradient temperature control program. Finally, the gas chromatograms of the standard methyl acetal gasoline solutions with different methyl acetal concentrations are obtained from the computer workstation 50.

[0086] By analyzing the gas chromatograms of standard methyl acetal gasoline solutions with different methyl acetal concentrations, the retention time of methyl acetal peaks in the gas chromatograms was determined and defined as the qualitative retention time of methyl acetal contained in gasoline.

[0087] By analyzing the peak area of ​​methyl acetal in the gas chromatograms of standard methyl acetal gasoline solutions with different concentrations of methyl acetal, the corresponding mass percentage of methyl acetal was determined. Then, using the three-point standard addition method, a calibration curve of methyl acetal peak area versus mass percentage of methyl acetal in gasoline was established based on the peak area values ​​of different methyl acetal mass percentages after passing the recovery rate test. This curve was defined as the quantitative calibration curve of methyl acetal mass percentage in gasoline.

[0088] The steps for detecting the methyl acetal content in gasoline include:

[0089] The gasoline sample to be tested was sealed and placed in the same refrigerated environment as the standard methylal gasoline solution for the same duration. The mass percentage of methylal in the gasoline sample should be ≤2.0%, or the mass percentage of methylal in the gasoline sample after dilution with methylal-free gasoline should be ≤2.0%.

[0090] Take out the gasoline sample that has completed the refrigeration process and place it in the chromatographic bottle matched with the injector 30. Start the detection system and let the injector 30 inject the gasoline sample into the detailed hydrocarbon analyzer 40 for detection. The detailed hydrocarbon analyzer 40 controls the column oven temperature according to the input column oven gradient temperature control program until the detection is completed. Then, the corresponding gas chromatogram of the gasoline sample is obtained through the computer workstation 50.

[0091] The peak in the gas chromatogram of the gasoline sample that matches the qualitative retention time of methyl acetal is identified as the methyl acetal peak of the gasoline sample. The corresponding methyl acetal mass percentage value is obtained from the quantitative calibration curve based on the area value of this methyl acetal peak, thus completing the detection of the methyl acetal content in the gasoline sample.

[0092] Furthermore, in the above steps, the preferred technical solution is:

[0093] The refrigeration environment is a cool, dark environment at 5°C, and the refrigeration time is 30 minutes.

[0094] The acceptable standard for recovery rate testing is set at 95%–105%.

[0095] The detailed hydrocarbon analyzer 40 is an Agilent 7890 Series II GC, and the capillary column 42 is a dimethyl silica capillary column. After the dimethyl silica capillary column has separated a set of samples, it is rinsed with 95% ethanol or anhydrous ethanol of analytical grade or higher. The detector 43 is a flame ionization detector, and the chromatographic data processing software is the Chemstation chemical analysis software system.

[0096] From the above description, it can be seen that:

[0097] This embodiment establishes a simple, convenient, and practical system and method for detecting methyl acetal content in gasoline by establishing a detection system, setting detection parameters and chromatographic separation procedures, determining the qualitative retention time and quantitative calibration curve of methyl acetal, and detecting the methyl acetal content in gasoline. It utilizes detection instruments and auxiliary equipment such as nitrogen source, hydrogen source, compressed air source, nitrogen flow meter, hydrogen flow meter, compressed air flow meter, injector, detailed hydrocarbon analyzer with vaporization chamber, capillary column and detector, and computer workstation with chromatographic data processing software.

[0098] In this embodiment, the temperature inside the injection port of the detection system is 250°C, the injection volume is 0.1 μL, the split ratio is 150:1, the detector temperature is 250°C, the flow rates of hydrogen and compressed air are 30 ml / min, the flow rate of nitrogen is 20 ml / min, and the column oven temperature of the detailed hydrocarbon analyzer is gradient temperature controlled. During detection, the corresponding gas chromatogram is first obtained by using a standard methylal gasoline solution to determine the peak retention time and peak area of ​​methylal contained in gasoline. This peak retention time is defined as the qualitative retention time of methylal contained in gasoline. The peak area values ​​of methylal corresponding to different methylal mass percentages after passing the recovery rate test are used to establish a calibration curve of the methylal mass percentage content in gasoline using the three-point standard addition method. This serves as the quantitative calibration curve of the methylal mass percentage content in gasoline, thereby detecting the methylal content in gasoline. These detection parameters and methods are novel and unique, ensuring satisfactory detection results.

[0099] The temperature inside the injection port is set at 250℃. This temperature setting not only ensures that all components in the sample can be completely vaporized instantly, thus allowing them to smoothly enter the capillary column for chromatographic separation, but more importantly, it avoids thermal decomposition of the components in the sample, which would affect the test results. In addition, setting the temperature inside the injection port at 250℃ also ensures that the sample flows smoothly throughout the entire flow path, including the injection port and the chromatographic column, without causing some high-boiling-point components to condense due to a temperature drop at a certain point in the transmission line, resulting in loss and peak tailing. It also ensures temperature matching with subsequent detection components, thereby further guaranteeing the best separation and detection effect of methyl acetal.

[0100] The 150:1 split ratio setting not only ensures that no relevant components in the sample are lost, but also ensures that each component in the sample is effectively separated, thereby obtaining a clear and complete gas chromatogram containing each component and ensuring the accuracy of the detection.

[0101] Furthermore, by controlling the column oven temperature through a gradient temperature control program, the capillary column can uniformly reach the set separation and detection temperature, ensuring consistent separation and detection conditions, thereby guaranteeing the separation effect and the accuracy of the detection data.

[0102] Furthermore, the detection method provided in this embodiment also includes a process of refrigerating the standard solution and the sample to be tested in a cool, dark environment at 5°C for 30 minutes. Experiments have shown that this refrigeration process can effectively eliminate the influence of ambient temperature on the volatilization of light hydrocarbon components in the sample, ensuring that all light hydrocarbon components in the sample, except for methane, are in a low-temperature liquefied state before vaporization separation. This effectively protects the light and volatile components in the sample and ensures the integrity of the sample. At the same time, through the designed column oven gradient temperature control program, the sample temperature is kept synchronized with the initial test column temperature set at 5°C, achieving effective cold trap focusing, thereby ensuring high resolution, high sensitivity, and high accuracy of the analytical results.

[0103] Experiments have shown that if the sample is injected directly into the chromatographic column without refrigeration, the initial bandwidth is too wide, resulting in broad peaks and poor resolution of the early eluent light hydrocarbons (such as ethane and propane), while the later eluent heavy hydrocarbon peaks are short and broad, especially methylal, making them difficult to identify and quantify effectively. The refrigeration process temperature of 5°C is not only much lower than the boiling point of the light hydrocarbon components, but also ensures that all components in the sample except methane (bp-161°C) can be effectively condensed. Furthermore, the sample after refrigeration, corresponding to the initial test column temperature of 5°C, can form a sharp initial sample band for differentiation and identification, without any loss.

[0104] The column oven gradient temperature control program, especially the initial test temperature set to 5℃, synchronized with the refrigeration temperature of the sample, enables effective cold trap focusing, allowing low-boiling-point substances to focus at the column head. The subsequent gradient uniform temperature ramp ensures that the capillary column reaches the set separation and detection temperature uniformly, allowing medium-boiling-point components in the sample to elute and separate quickly, saving separation time and ensuring consistent separation and detection conditions, thus guaranteeing separation efficiency. Finally, the column oven temperature reaches 250℃, ensuring that all high-boiling-point substances in the sample are separated and flushed out, guaranteeing column cleanliness and maintaining consistency with the detector temperature, resulting in smoother detection and more accurate data.

[0105] As can be seen, the method for detecting methyl acetal content in gasoline provided in this embodiment is a creative application of DHA technology in the detection of methyl acetal in gasoline. Experiments have shown that this detection method, when used to detect gasoline containing methyl acetal at a mass percentage of ≤2.0%, or gasoline diluted with methyl acetal-free gasoline containing methyl acetal at a mass percentage of ≤2.0%, exhibits excellent linearity in its quantitative calibration curve, high detection sensitivity, and good accuracy. It can fully realize the application potential of DHA technology, thus making it an effective and practical technical means for detecting methyl acetal in gasoline. It effectively solves the problems of convenience and economy in practical applications. Therefore, it can be widely used in the market supervision and quality control of blended gasoline, effectively curbing the illegal addition of methyl acetal to gasoline, thereby protecting consumer rights and environmental safety.

[0106] To further help understand the specific implementation method and technical effects of the method for detecting methyl acetal content in gasoline provided in this embodiment, the following will provide further explanation through specific examples and comparative examples. However, for the sake of brevity, some of the same steps will only be described briefly. Case

[0107] like Figure 1 As shown, following the assembly steps of the detection system in the above embodiments, an Agilent 7890 Series II GC detailed hydrocarbon analyzer (high-yield gas chromatograph) equipped with a dimethyl silica capillary column and a flame ionization detector is connected with an Agilent automated liquid sampler, a computer workstation with Chemstation chemical analysis software installed, and nitrogen, hydrogen, compressed air sources, nitrogen flow meters, hydrogen flow meters, compressed air flow meters, nitrogen purifiers, hydrogen purifiers, and air purifiers that meet the requirements of chromatographic analysis to form a gasoline methyl acetal content detection system.

[0108] The detection parameters of the assembled detection system were set as follows: the temperature inside the inlet of the Agilent automated liquid sampler was set to 250°C; the injection volume of the Agilent automated liquid sampler was set to 0.1 μL per injection; the split ratio of the vaporization chamber was set to 150:1; the temperature of the hydrogen flame ionization detector was set to 250°C; the flow rates of the hydrogen flow meter and compressed air flow meter were set to 30 ml / min; the flow rate of the nitrogen flow meter was set to 20 ml / min; and the temperature control program of the column oven of the detailed hydrocarbon analyzer was set as follows: the initial temperature was 5°C, held for 10 minutes, then increased to 50°C at a rate of 5°C / min, held for 50 minutes, then increased to 200°C at a rate of 1.5°C / min, held for 5 minutes, then increased to 250°C, and held at this temperature until the detection was completed.

[0109] Using gasoline without methyl acetal as a solvent, methyl acetal standards were prepared into four standard methyl acetal gasoline solutions with different concentration gradients of 0.0%, 0.5%, 1.0% and 2.0% by mass. Each standard methyl acetal gasoline solution was then placed in a cool, dark environment at 5°C for 30 minutes.

[0110] The detection system was turned on, and four standard methylal gasoline solutions with different concentrations, having undergone refrigeration, were injected sequentially into an Agilent 7890 Series II GC detailed hydrocarbon analyzer using an Agilent automated liquid sampler. The analyzer then performed gas chromatography separation and flame ionization detection on each of the four standard methylal gasoline solutions according to the pre-entered column oven gradient temperature control program. Gas chromatograms of the corresponding methylal gasoline solutions with different concentrations were then acquired from a computer workstation equipped with ChemStation chemical analysis software. The ChemStation software was used to correct the obtained gas chromatograms, determining the retention time and peak area of ​​methylal, and rounding the results to 0.01%. The results report was then printed out. Figure 2 The image shows the gas chromatogram of a standard methylal gasoline solution with a methylal content of 0.5% provided in this case. Figure 3 The image shows the gas chromatogram of a standard methyl acetal gasoline solution with a mass percentage of 1.0% provided in this case. Figure 4 The image shows the gas chromatogram of a standard methyl acetal gasoline solution with a mass percentage of 2.0% provided in this case.

[0111] pass Figures 2 to 4 The gas chromatogram of the standard methyl acetal gasoline solution shown indicates that the retention time of methyl acetal in the gas chromatogram of the standard methyl acetal gasoline solution is 23.095 min, which means that the qualitative retention time of methyl acetal in gasoline is 23.095 min.

[0112] Will Figures 2 to 4 The peak areas of methyl acetal in the gas chromatograms of methyl acetal gasoline solutions with different methyl acetal contents, as shown in the figure, were plotted using the three-point standard addition method to establish a [data structure]. Figure 5 The figure shown is a calibration curve of the peak area of ​​methyl acetal and the mass percentage of methyl acetal in the standard methyl acetal gasoline solution provided in this invention. The linearity result is 0.99994.

[0113] Recovery rates were obtained by analyzing the methyl acetal content values ​​of standard methyl acetal gasoline solutions with different methyl acetal contents in the calibration curve of the methyl acetal peak area-mass percentage content of the above standard methyl acetal gasoline solutions. The results are shown in Table 1 below, where the standard serial number refers to the serial number of the standard methyl acetal gasoline solution.

[0114] Table 1

[0115]

[0116] The recovery rates shown in Table 1 indicate that:

[0117] In this case, the recovery rates of methyl acetal content in standard methyl acetal gasoline solutions with different methyl acetal contents were all within an acceptable range of 95% to 105%. Therefore... Figure 5 The peak area-mass percentage content calibration curve of methyl acetal, plotted using the gas chromatogram of the standard methyl acetal gasoline solution given in this case, can be used as a quantitative calibration curve for the mass percentage content of methyl acetal in gasoline.

[0118] The data listed in Table 2 are the results of testing multiple gasoline samples containing methyl acetal, based on the qualitative retention time of methyl acetal and the quantitative calibration curve of the mass percentage of methyl acetal in gasoline. The specific testing process includes:

[0119] Each gasoline sample to be tested was initially tested to determine that the mass percentage of methyl acetal contained in each sample was ≤2.0%, or that the mass percentage of methyl acetal contained in each gasoline sample after dilution with methyl acetal-free gasoline was ≤2.0%. Then, each gasoline sample was divided into three groups of gasoline samples with contents of 0.5%, 1.0% and 2.0% according to their pre-tested methyl acetal content. Each group of samples was then sealed and placed in the same cold storage environment as the standard methyl acetal gasoline solution for the same duration.

[0120] Take out a set of gasoline samples that have completed the refrigeration process, start the detection system, and let the Agilent automatic liquid sampler draw 0.1 μL of sample from each gasoline sample in this set. Then, automatically inject the sample into the vaporization chamber of the Agilent 7890 Series IIGC detailed hydrocarbon analyzer. The detailed hydrocarbon analyzer follows the input column oven gradient temperature control program, that is: the initial temperature is 5°C, hold for 10 minutes, then increase the temperature to 50°C at a rate of 5°C / min, hold for 50 minutes, then increase the temperature to 200°C at a rate of 1.5°C / min, hold for 5 minutes, then increase the temperature to 250°C, and then hold this temperature until the separation and detection are completed. Perform gas chromatography separation and detection on each gasoline sample. Finally, process the obtained detection data and round the results to 0.01% using the Chemstation chemical analysis software system built into the computer workstation to obtain the gas chromatogram of each corresponding gasoline sample.

[0121] After a set of gasoline samples has been tested, the dimethyl silica capillary column in the detailed hydrocarbon analyzer is flushed with 95% ethanol or anhydrous ethanol of analytical grade or higher until the baseline is straight. Then, the second set of samples is tested in the same way. The capillary column is flushed and the third set of samples is tested. After the tests are completed, the capillary column is flushed again and set aside for later use.

[0122] The peak in the gas chromatogram of the obtained gasoline sample that matches the qualitative retention time of methyl acetal is identified as the methyl acetal peak of that gasoline sample. The corresponding methyl acetal mass percentage value is obtained from the methyl acetal peak area-mass percentage content correction curve based on the area value of this methyl acetal peak, thus completing the detection of the methyl acetal content of each gasoline sample.

[0123] Based on the data listed in Table 2, we can obtain the following respectively: Figure 6 The image shows the test results of methyl acetal content in each gasoline sample of the 0.5% methyl acetal group provided in this case study. Figure 7 The image shows the test results of methyl acetal content in each gasoline sample of the 1.0% methyl acetal group provided in this case study. Figure 8 The figure shown is a graph of the methyl acetal content test results for each gasoline sample in the methyl acetal group with a mass percentage concentration of 2.0% provided in this case.

[0124] From the data listed in Table 2 and Figures 6 to 8 It can be seen from this:

[0125] 1) The test results of the content of methyl acetal in gasoline obtained by the detection method given in this embodiment have good repeatability and can meet the requirement that the relative standard deviation (RSD) of high efficiency gas chromatography data is ≤2.0%;

[0126] 2) The recovery rates of each sample group were 98%, 98% and 101%, respectively, which fully meet the requirement that the recovery rate of content detection should be 95-105%.

[0127] From this, we can draw the following conclusion:

[0128] By employing DHA (Detailed Hydrocarbon Analyzer) technology and combining the detection parameters and procedures provided in this embodiment, the content of methylal in gasoline can be detected, yielding good qualitative and quantitative results with accurate and reliable data. The operation method is simple and practical, effectively solving the issues of convenience and economy in practical applications. It can be widely used in the market supervision and quality control of blended gasoline, effectively curbing the illegal addition of methylal to gasoline and protecting consumer rights and environmental safety.

[0129] Table 2

[0130] Comparative Example

[0131] First, following the preparation method of the standard methylal gasoline solution in the above case, five methylal gasoline standard solutions were prepared. Then, these five methylal gasoline standard solutions were subjected to infrared spectroscopy detection according to the People's Republic of China's "Identification and Determination of Typical Unconventional Additives in Automotive Gasoline - Infrared Spectroscopy Method" (Standard No.: GB / T 33648-2017). The detection results were compiled as follows. Figure 9 The figure shown is a content correction curve of the methyl acetal gasoline standard solution provided in this comparative example using infrared spectroscopy.

[0132] from Figure 9 The table in Table 3 shows the methyl acetal content values ​​obtained by detecting the methyl acetal content of each methyl acetal gasoline standard solution using the prescribed infrared spectroscopy method.

[0133] Table 3

[0134]

[0135] right Figure 9 By calibrating the relevant data listed in Table 3, the calibration results shown in Table 4 can be obtained.

[0136] Table 4

[0137]

[0138] from Figure 9 As can be seen from Tables 3 and 4:

[0139] The existing infrared spectroscopy method for detecting methyl acetal in gasoline has a large error, which is not as good as the detection results that can be achieved by the technical solution given in this invention.

[0140] In conclusion, it can be seen that:

[0141] This invention establishes a simple, convenient, and practical system and method for detecting methyl acetal content in gasoline through steps such as the construction of a detection system, the setting of detection parameters and chromatographic separation procedures, the determination of qualitative retention time and quantitative calibration curve of methyl acetal, and the detection of methyl acetal content in gasoline. It utilizes detection instruments and auxiliary equipment such as nitrogen source, hydrogen source, compressed air source, nitrogen flow meter, hydrogen flow meter, compressed air flow meter, injector, detailed hydrocarbon analyzer with vaporization chamber, capillary chromatographic column and detector, and computer workstation with chromatographic data processing software.

[0142] The method for detecting methyl acetal content in gasoline provided by this invention is a creative application of DHA technology in the detection of methyl acetal in gasoline. Experiments have shown that this detection method, when used to detect gasoline containing methyl acetal at a mass percentage ≤2.0%, or gasoline diluted with methyl acetal-free gasoline containing methyl acetal at a mass percentage ≤2.0%, exhibits excellent linearity in its quantitative calibration curve, high detection sensitivity, and good accuracy. It fully leverages the application potential of DHA technology, making it an effective and practical technical means for detecting methyl acetal in gasoline. This effectively solves the problems of convenience and economy in practical applications and can be widely used in the market supervision and quality control of blended gasoline, effectively curbing the illegal addition of methyl acetal to gasoline, thereby protecting consumer rights and environmental safety. Therefore, it has outstanding beneficial effects and significant progress, and is of great value for promotion and application.

[0143] In the description process of the above instruction manual:

[0144] The terms “this embodiment,” “this embodiment of the invention,” “this case,” “this comparative example,” “as shown,” “further,” etc., are used to indicate that the specific features, structures, materials, or characteristics described in the embodiment or case or comparative example are included in at least one embodiment or case or comparative example of the present invention.

[0145] In this specification, the illustrative expressions of the above terms are not necessarily specific to any particular embodiment, case, or comparative example. Moreover, the specific features, structures, materials, or characteristics described may be combined or combined in any suitable manner in one or more embodiments, cases, or comparative examples. Furthermore, without creating contradictions, those skilled in the art may combine or combine the different embodiments, cases, or comparative examples described in this specification, as well as the features in the different embodiments, cases, or comparative examples.

[0146] Finally, it should be noted that:

[0147] The above embodiments and examples are only used to illustrate the technical solutions and technical effects of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, examples, and comparative examples, those skilled in the art should understand that modifications or additions can still be made to the technical solutions or technical effects described in the foregoing embodiments, examples, and comparative examples, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the embodiments of the present invention. Non-essential improvements, adjustments, or substitutions made by those skilled in the art based on the content of this specification are all within the scope of protection claimed by the present invention.

Claims

1. A method for detecting the methyl acetal content in gasoline, used to detect the mass percentage of methyl acetal in gasoline, wherein the mass percentage of methyl acetal in the gasoline should be ≤2.0%, or the mass percentage of methyl acetal in the gasoline after dilution with methyl acetal-free gasoline should be ≤2.0%, characterized in that, Includes the following steps: The steps for setting up the detection system, configuring detection parameters and chromatographic separation procedures, determining the qualitative retention time and quantitative calibration curve for methyl acetal, and detecting the methyl acetal content in gasoline, including: The detection system includes a nitrogen source, a hydrogen source, a compressed air source, a nitrogen flow meter, a hydrogen flow meter, a compressed air flow meter, an injector, a detailed hydrocarbon analyzer with a vaporization chamber, a capillary chromatographic column and a detector, and a computer workstation with chromatographic data processing software. The steps for assembling the detection system include: Connect the nitrogen source, hydrogen source, and compressed air source to the nitrogen flow meter, hydrogen flow meter, and compressed air flow meter respectively using pipes. Then connect the output end of the nitrogen flow meter to the vaporization chamber of the detailed hydrocarbon analyzer. Connect the output ends of the hydrogen flow meter and compressed air flow meter to the detector of the detailed hydrocarbon analyzer. Connect the injector to the vaporization chamber. Connect the capillary chromatographic column between the vaporization chamber and the detector. Finally, connect the signal line of the detector to the computer workstation. The steps for setting the detection parameters and chromatographic separation program include: The temperature inside the injection port of the injector is set to 250°C, the injection volume of the injector is set to 0.1 μL, the split ratio of the vaporization chamber is set to 150:1, the temperature of the detector is set to 250°C, the flow rates of the hydrogen flow meter and the compressed air flow meter are set to 30 ml / min, the flow rate of the nitrogen flow meter is set to 20 ml / min, the temperature control program of the column oven of the detailed hydrocarbon analyzer is set to the column oven gradient temperature control program, and the set column oven gradient temperature control program is input into the controller of the detailed hydrocarbon analyzer. The steps for determining the qualitative retention time and quantitative calibration curve of methyl acetal include: Using gasoline without methyl acetal as a solvent, methyl acetal standards were prepared into standard methyl acetal gasoline solutions with a mass percentage in the range of 0 to 2.0% and containing at least four different concentration gradients of 0 and 2.0%. Each of the standard methyl acetal gasoline solutions was then placed in a cool environment for refrigeration. The detection system is turned on, and standard methyl acetal gasoline solutions with different methyl acetal concentrations that have completed the refrigeration process are injected one by one into the detailed hydrocarbon analyzer through the injector. The detailed hydrocarbon analyzer performs gas chromatography separation and detection on the standard methyl acetal gasoline solutions one by one according to the input column oven gradient temperature control program. Finally, gas chromatograms of standard methyl acetal gasoline solutions with different methyl acetal concentrations are obtained from the computer workstation. By analyzing the gas chromatograms of the standard methyl acetal gasoline solutions with different methyl acetal concentrations, the retention time of the methyl acetal peak in the gas chromatogram was determined and defined as the qualitative retention time of the methyl acetal contained in the gasoline. The methyl acetal mass percentage was determined by the peak area of ​​methyl acetal in the gas chromatogram of standard methyl acetal gasoline solutions with different concentrations of methyl acetal. The methyl acetal peak area corresponding to different methyl acetal mass percentages after passing the recovery test was used to establish a methyl acetal peak area-mass percentage content calibration curve in gasoline using the three-point standard addition method. This curve was defined as the quantitative calibration curve of methyl acetal mass percentage in gasoline. The detection steps for the methyl acetal content in the gasoline include: The gasoline sample to be tested is sealed and placed in the same refrigeration environment as the standard methylal gasoline solution for the same duration. The mass percentage of methylal in the gasoline sample should be ≤2.0%, or the mass percentage of methylal in the gasoline sample after dilution with methylal-free gasoline should be ≤2.0%. Take out the gasoline sample that has completed the refrigeration process and place it in the chromatographic vial that is matched with the injector. Start the detection system and let the injector inject the gasoline sample into the detailed hydrocarbon analyzer for detection. The detailed hydrocarbon analyzer controls the column oven temperature according to the input column oven gradient temperature control program until the detection is completed. Then, the corresponding gas chromatogram of the gasoline sample is obtained through the computer workstation. The peak in the gas chromatogram of the gasoline sample that matches the qualitative retention time of methyl acetal is identified as the methyl acetal peak of the gasoline sample. The corresponding methyl acetal mass percentage value is obtained from the quantitative calibration curve based on the area value of this methyl acetal peak, thus completing the detection of the methyl acetal content of the gasoline sample.

2. The method for detecting the content of methyl acetal in gasoline as described in claim 1, characterized in that: The detailed column oven gradient temperature control program of the hydrocarbon analyzer is as follows: the initial temperature of the column oven is set to 5°C, held for 10 minutes, then increased to 50°C at a rate of 5°C / minute, held for 50 minutes, then increased to 200°C at a rate of 1.5°C / minute, held for 5 minutes, then increased to 250°C, and then held at this temperature until the detection is completed.

3. The method for detecting the content of methyl acetal in gasoline as described in claim 1, characterized in that: The refrigeration environment is a cool, dark environment at 5°C, and the refrigeration time is 30 minutes.

4. The method for detecting the content of methyl acetal in gasoline as described in claim 1, characterized in that: The standard for passing the recovery rate test is a recovery rate of 95% to 105%.

5. The method for detecting the content of methyl acetal in gasoline as described in claim 1, characterized in that: The detailed hydrocarbon analyzer is an Agilent 7890 Series II GC, and the injector is an Agilent automated liquid sampler.

6. The method for detecting the content of methyl acetal in gasoline as described in claim 5, characterized in that: The detailed hydrocarbon analyzer uses a dimethyl silica capillary column.

7. The method for detecting the content of methyl acetal in gasoline as described in claim 6, characterized in that: After the dimethyl silica capillary column has separated a set of samples, it is washed with 95% ethanol or anhydrous ethanol of analytical grade or higher.

8. The method for detecting the content of methyl acetal in gasoline as described in claim 5, characterized in that: The detailed hydrocarbon analyzer uses a hydrogen flame ionization detector.

9. The method for detecting the content of methyl acetal in gasoline as described in claim 1, characterized in that: The chromatographic data processing software is the Chemstation chemical analysis software system.

10. The method for detecting the content of methyl acetal in gasoline as described in claim 1, characterized in that: The detection system also includes a nitrogen purifier, a hydrogen purifier, and an air purifier; The nitrogen purifier, the hydrogen purifier, and the air purifier are each connected at both ends to the corresponding nitrogen source, hydrogen source, and compressed air source, as well as the nitrogen flow meter, the hydrogen flow meter, and the compressed air flow meter.

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