Method for detecting residual mineral oil in edible oil

Abstract

The invention discloses a method for detecting residual mineral oil in edible oil. According to the method, only sulfuric acid silica gel is used for purification, expensive special equipment is not depended on, and traceability analysis of residual mineral oil and quantitative analysis of saturated hydrocarbon mineral oil can be carried out only by using common GC-FID (Gas Chromatography-Flame Ionization Detector).

Description

Technical Field

[0001] The present application relates to the technical field of food analysis, and in particular to a method for detecting residual mineral oil in edible oil. Background Art

[0002] There is a risk of mineral oil contamination during the production and transportation of edible oils, including raw material contamination, mineral oil leakage during processing, packaging material contamination, and contamination caused by illegal operations during transportation. Mineral oil may pose a potential threat to human health, including digestive system disorders, nervous system damage, and endocrine disruption. The detection methods for mineral oil in edible oils mainly include qualitative methods and quantitative methods. At present, the domestic standard method only has qualitative methods. GB / T 5539-2008 "Qualitative Test for Oils and Fats in Grain and Oil Inspection" stipulates the qualitative detection method of mineral oil in edible oils. The principle is that oils and fats are saponified in potassium hydroxide-ethanol solution. Mineral oils that cannot be saponified cannot be dissolved in ethanol solution, which will produce turbidity or precipitation. The method is not suitable for rice bran crude oil and sea buckthorn oil. The saponification method principle in GB / T 37514-2019 "Detection of Mineral Oils in Animal and Plant Oils and Fats" is the same as GB / T 5539-2008, and the detection limit is 0.5%. The principle of alumina thin layer chromatography is that animal and plant oils and mineral oils have different polarities and can be separated by thin layer chromatography, using a color developer to develop color, observing with ultraviolet light, and comparing with oil standards and liquid paraffin standards to determine whether there is a mineral oil component. This method is not suitable for dark sea buckthorn fruit oil, and the detection limit is 0.3%. The saponification method in the above method relies more on subjective identification, and after actual testing, different types of mineral oils have different thresholds for turbidity, and there are many false negatives in the test results. The existing quantitative method is EN 16995-2017 "Foodstuffs - Vegetable oils and foodstuff on basis of vegetable oils -Determination of mineral oil saturated hydrocarbons (MOSH) and mineral oilaromatic hydrocarbons (MOAH) with on-line HPLC-GC-FID analysis". This method is suitable for the quantitative detection of C10-C50 saturated hydrocarbons mineral oil (MOSH) and mineral oil aromatic hydrocarbons (MOAH) in vegetable oils and fats. The principle of the method is to use HPLC to separate and transfer to GC-FID analysis. For samples with more interference, activated alumina is used to adsorb normal alkanes or epoxidized unsaturated hydrocarbons and then remove impurities. It is more accurate when the MOSH content is higher than 10 mg / kg. It is currently the most advanced mineral oil detection method, but it requires online HPLC-GC-FID equipment, which is dedicated to mineral oil detection and is expensive (each unit costs more than 1.5 million yuan). It cannot be used for other project detection. Affected by the market size, it is difficult to meet the urgent needs of the market when a food safety incident breaks out.

[0003] Therefore, there is still an urgent need to develop a rapid, simple, and versatile determination method suitable for the quality control of edible oils. Summary of the invention

[0004] The purpose of the present application is to provide a method for detecting residual mineral oil in edible oil, which method does not rely on expensive special equipment and can carry out traceability analysis of residual mineral oil and quantitative analysis of saturated hydrocarbon mineral oil using only ordinary GC-FID.

[0005] The present application provides a method for detecting residual mineral oil in edible oil, which adopts the following technical scheme: A method for detecting residual mineral oil in edible oil, comprising the following steps: 1) Extraction: Weigh edible oil and dissolve it to obtain an extract containing mineral oil; 2) Purification: transferring the extract obtained in step 1) to a purification column, and eluting the purification column to obtain an eluate; 3) Concentration: The eluate collected in step 2) is concentrated by rotary evaporation under the conditions of an end point pressure of not less than 300 hPa and a water bath temperature of not more than 40°C. When the eluate is concentrated to less than 1 mL, nitrogen is blown at room temperature to obtain a concentrated solution; 4) Detection: The concentrated solution obtained in step 3) is detected by gas chromatography-hydrogen flame ionization detector to obtain a spectrum; 5) Analysis: Conduct source analysis of mineral oil and quantitative analysis of saturated hydrocarbon mineral oil based on the spectrum obtained in step 4); Wherein, the purification column comprises sulfuric acid silica gel.

[0006] By adopting the above technical solution, the purification steps are simple, the concentration time is short, and the traceability analysis of residual mineral oil and the quantitative analysis of saturated hydrocarbon mineral oil can be completed simultaneously by one gas chromatography-hydrogen flame ionization detection.

[0007] Optionally, the ratio of the silica gel with sulfuric acid to the eluent is 1 g: 2-4 mL; preferably, the ratio is 1 g: 3 mL.

[0008] By adopting the above technical solution, it can be ensured that the saturated hydrocarbons with a high carbon number are completely eluted, the results are more accurate and no reagent waste is caused.

[0009] Optionally, the mass ratio of the silica gel sulfate to the edible oil is 15-20:1; preferably, the ratio is 20:1.

[0010] By adopting the above technical solution, a good purification effect can be achieved without purification overload.

[0011] Optionally, the purification column comprises from bottom to top: glass wool, anhydrous sodium sulfate, neutral silica gel, sulfate silica gel, a mixture of equal mass, and anhydrous sodium sulfate.

[0012] Optionally, the mixture of equal masses consists of anhydrous sodium sulfate and silica gel sulfate.

[0013] By adopting the above technical solution, a better buffering effect can be achieved during purification, elution is more complete and column efficiency is improved.

[0014] Optionally, the sulfuric acid content of the sulfuric acid silica gel is 30%-33%; preferably, the sulfuric acid content of the sulfuric acid silica gel is 33%.

[0015] By adopting the above technical solution, fat in edible oil can be better removed and carbonization can be avoided.

[0016] Optionally, when eluting the purification column in step 2), the flow rate is controlled to be 2 mL / min.

[0017] By adopting the above technical solution, an optimal balance can be achieved among elution effect, column efficiency and reagent dosage.

[0018] Optionally, the vessel used in step 1) to step 3) is made of glass.

[0019] By adopting the above technical solution, C 14 The previous spectrum had fewer noise peaks.

[0020] Optionally, the endpoint pressure in step 3) is 330 hPa and the water bath temperature is 40°C.

[0021] By adopting the above technical solution, the loss of characteristic peaks of mineral oil is significantly reduced, ensuring that the detection method can well perform traceability analysis of mineral oil in edible oil.

[0022] Optionally, the mineral oil in the traceability analysis in step 5) is selected from kerosene, diesel or liquid paraffin.

[0023] By adopting the above technical solution, pollution source tracing analysis of kerosene, diesel or liquid paraffin is achieved.

[0024] In summary, the present application includes at least one of the following beneficial technical effects: 1. The purification method involved has parallel processing capabilities, is not limited by the number of instruments, and can better cope with large batches of samples; It does not rely on expensive special equipment, such as PTV-GC-FID and HPLC-GC-FID, but only uses ordinary GC-FID, which significantly reduces the detection cost, and almost all analytical laboratories can directly carry out the present invention; Through the specific purification and concentration method of the present application, the steps are relatively simple, and a single GC-FID test can simultaneously complete the traceability analysis of residual mineral oil and the quantitative analysis of saturated hydrocarbon mineral oil, achieving a multifunctional analytical application; 4. It has the ability to trace the source of pollution, which is not available in existing domestic and international standards. Tracing the source of pollution plays a significant role in promoting the proper handling of food safety incidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is shown as C 10 -C 33 Total area integration method within the range; Figure 2 It is shown as C 10 -C 33 Area integration method for sharp peaks within the range; Figure 3 Shown is a gas chromatogram of a diesel sample of the present invention; Figure 4 Shown is an overlay of gas chromatograms of a soybean oil sample (upper) contaminated by diesel fuel and a blank sample (lower) according to the present invention; Figure 5 Shown is a gas chromatogram of a kerosene sample of the present invention; Figure 6 Shown is an overlay of gas chromatograms of a soybean oil sample (upper) contaminated with kerosene and a blank sample (lower) according to the present invention; Figure 7 Shown is a gas chromatogram of a liquid paraffin sample of the present invention; Figure 8 Shown is an overlay of gas chromatograms of a soybean oil sample contaminated with liquid paraffin (upper) and a blank sample (lower) according to the present invention. DETAILED DESCRIPTION

[0026] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical scheme of the present invention is described in detail below in conjunction with the following specific embodiments and the accompanying drawings of the specification, but it should not be understood as limiting the scope of implementation of the present invention.

[0027] n-Hexane (pesticide grade, Xingke), anhydrous sodium sulfate (superior grade, Sinopharm), concentrated sulfuric acid (superior grade, Leybold), silica gel for chromatography column (70-230 mesh), glass wool (CNW), n-alkane standard (C 10 -C 40 , 1000 μg / mL in cyclohexane, ink quality inspection).

[0028] 1.1 Extraction Use a Bath pipette to draw 0.5 g of edible oil into a nitrogen blowpipe, add a small amount of n-hexane to fully dissolve it to obtain a n-hexane extract.

[0029] 1.2 Purification Take a glass chromatography column with a piston, add glass wool, 1 g anhydrous sodium sulfate, 2 g neutral silica gel, 10 g 33% sulfuric acid silica gel, 2 g anhydrous sodium sulfate and 33% sulfuric acid silica gel, 1 g anhydrous sodium sulfate, dry fill the column, activate with 20 mL n-hexane, close the piston when the liquid level drops to 2 mm from the top of the filler, and wait for the sample to be loaded. Use a Bass pipette to transfer the n-hexane extract to the purification column, wash the nitrogen blowpipe with 1 mL n-hexane each time, for a total of 3 times, transfer all the washing liquid to the purification column, connect a 250 mL chicken heart bottle, use 30 mL n-hexane to elute, and control the flow rate at 2 mL / min (passing the column at a flow rate of 2 mL / min can achieve the best balance of elution effect, column efficiency and reagent dosage). Sulfuric acid silica gel is prepared by adding high-grade pure concentrated sulfuric acid to 0.5 times the mass of silica gel after neutral silica gel is removed at 550°C for 4 hours to remove the background; the anhydrous sodium sulfate is activated at 550°C for 4 hours. If silica gel and anhydrous sodium sulfate are not cleaned with n-hexane and activated at high temperature, the impurities they contain will interfere with the spectrum.

[0030] 1.3 Concentration The eluate was concentrated to 500 μL using a rotary evaporator at an initial pressure of 500 hPa, an end pressure of 330 hPa, and a water bath temperature of 40°C. The eluate was then transferred to a KD concentrator tube with a 0.1 mL scale and slowly purged with nitrogen at room temperature (20-25°C) to below the scale line of 100 μL. The volume was then made up to 0.1 mL with n-hexane.

[0031] 1.4 Detection The samples were detected by gas chromatography-flame ionization detector (GC-FID).

[0032] Gas chromatography conditions: chromatographic column: DB-5ms, 30 m × 0.25 mm × 0.25 μm or equivalent column; programmed temperature: initial temperature 50 ℃, increase to 60 ℃ at 2.5 ℃ / min, increase to 280 ℃ at 22 ℃ / min, increase to 315 ℃ at 25 ℃ / min, and hold for 16 min; injection port temperature: 300 ℃; injection volume: 1 μL; injection mode: splitless injection.

[0033] Flame ionization detection conditions: detector temperature 340 °C, high-purity nitrogen, flow rate 1.5 mL / min.

[0034] 1.5 Origin Analysis When there is mineral oil contamination in edible oil, the potential source of contamination can be determined based on the standard spectra of kerosene, diesel and liquid paraffin. Compare the soybean oil sample contaminated by mineral oil with the standard gas chromatogram of mineral oil. Liquid paraffin can be qualitatively determined based on the position of the bulge peak, and kerosene and diesel can be qualitatively determined based on the characteristic peaks of normal alkanes and the position of the bulge peak.

[0035] 1.6 Quantitative analysis Saturated hydrocarbon mineral oil exists in the form of a bulge peak (UCM) in the spectrum. The mineral oil that contaminates edible vegetable oil is almost entirely composed of branched alkanes and cycloalkanes. Sharp peaks are usually considered to be normal alkanes, terpenes, squalene and their isomerization products, as well as sterenes and alkenes with carotenoid structures. Therefore, the content of saturated hydrocarbon mineral oil is quantified by the bulge peak area using the external standard method. The bulge peak area is equal to the total area within the range ( Figure 1 ) minus the sharp peak area ( Figure 2 ). Use C 10 -C 40 The standard curve is drawn with the average response factor, and the calculation formula is as follows:

[0036] Where: X—the content of saturated hydrocarbon mineral oil in the sample, in milligrams per kilogram (mg / kg); c1—the concentration corresponding to the total area in the sample solution obtained from the standard curve, in micrograms per milliliter (μg / mL); c2—the concentration corresponding to the sharp peak in the sample solution obtained from the standard curve, in micrograms per milliliter (μg / mL); V—sample solution fixed volume, in milliliters (mL); m—sample mass, in grams (g).

[0037] 2.1 Limit of quantification and limit of detection Saturated hydrocarbon mineral oil is a series of compounds with unknown quantity and composition. The characteristics of this type of compounds are that they are all alkanes (including chain hydrocarbons and cyclic hydrocarbons). Due to their similar properties and wide variety, they cannot be effectively separated in the spectrum and overlap to form a group of peaks resembling bulges. When quantifying, it is necessary to add and calculate the peak areas of all peaks within the range. Interference peaks not derived from samples include miscellaneous peaks from the GC system and reagent consumables. These miscellaneous peaks may be counted as bulge peaks representing saturated hydrocarbon mineral oil in data processing, resulting in changes in the results. Such situations can be regarded as miscellaneous peaks in the blank as background. According to Appendix A of HJ 168-2020, for the detection of target objects in blank tests, the allowable difference range between any measured values ​​is within "the mean of the blank test measured values ​​± 1 / 2 of the estimated detection limit". According to the quantitative analysis method of Example 1, 9 blank tests were carried out. In order to most strictly evaluate the blank interference situation, the C 10 -C 40 The peaks and baseline bulges within the range were summed up, and the results of the nine tests were 11.9, 11.0, 13.9, 14.5, 14.3, 14.2, 14.1, 13.8, and 14.7 μg / mL, respectively. The method detection limit was calculated according to the following formula: MDL=t (n-1,0.99) ×S Where MDL is the method detection limit, t (n-1,0.99) is the t distribution value when the degree of freedom is n-1 and the confidence level is 99%, S is the standard deviation of n parallel measurements. Looking up the t value table, we can see that when n=9, the degree of freedom is 8, and t=2.896. At this time, the calculated method detection limit is 4.62 μg / mL. When the sampling amount is 0.5 g and the final fixed volume is 0.1 mL, the method detection limit is 0.74 mg / kg and the method quantification limit is 2.2 mg / kg.

[0038] 2.2 Recovery rate of mineral oil in edible oil According to the detection method in Example 1, kerosene, diesel and liquid paraffin were spiked at 100 mg / kg on soybean oil, and the recoveries after background subtraction were 105%, 76% and 93%, respectively. Five other edible oils were selected, and kerosene with a saturated hydrocarbon mineral oil concentration of 100 mg / kg was spiked. The recovery results are shown in Table 1 below. It can be seen from the results that the detection method can be used for the quantitative detection of residual mineral oil in various edible oils.

[0039] Table 1 Sample name Kerosene recovery rate% tea oil 90 Sunflower Oil 71 Soybean Oil (another brand) 102 Rapeseed Oil 83 Corn Oil 80 2.3 Origin Analysis Figure 4 , Figure 6 and Figure 8In order to better see the difference between contaminated samples and uncontaminated samples (i.e. blank samples), the gas chromatograms of the two are superimposed.

[0040] Figure 3 This is the gas chromatogram of the diesel sample, with the bulge peak range C 10 -C 28 , and has obvious C 13 -C 17 Characteristic peaks of normal alkanes. Figure 4 The gas chromatograms of the soybean oil sample (upper) and the blank sample (lower) contaminated by diesel in the present invention are superimposed, with obvious C 13 -C 17 The characteristics of normal alkanes (soybean oil does not have this characteristic), and the bulge peak appears at the corresponding position at the same time, which can be judged that the sample is contaminated by diesel.

[0041] Figure 5 This is the gas chromatogram of the kerosene sample, with the bulge peak range C 10 -C 14 , and has obvious C 11 -C 14 Characteristic peaks of normal alkanes. Figure 6 The gas chromatograms of the soybean oil sample (upper) and the blank sample (lower) contaminated by kerosene in the present invention are superimposed, with obvious C 11 -C 14 The presence of a bulge peak at the corresponding position indicates that the sample is contaminated with kerosene.

[0042] Figure 7 This is the gas chromatogram of the liquid paraffin sample, with the bulge peak range C 20 -C 35 , there is no obvious characteristic peak of normal alkane. Figure 8 The gas chromatograms of the soybean oil sample (upper) and the blank sample (lower) contaminated by liquid paraffin in the present invention are superimposed, with obvious C 20 -C 35 The location of the bulge peak can be used to determine whether the sample is contaminated with liquid paraffin.

[0043] Example 3 Effects of using different methods The test results obtained by different methods show that the final test results are significantly different when using different purification steps, concentration steps, and materials. Even if the principles of some steps are the same, there are still test results that are difficult to predict in advance. For the convenience of comparison, different methods and test results are summarized in the following Tables 2 and 3.

[0044] 3.1 Comparison of different purification methods The oil alkaline hydrolysis-n-hexane extraction method is as follows: take an appropriate amount of sample, add potassium hydroxide ethanol solution, heat and react for 30 minutes until all the oil is completely hydrolyzed, use n-hexane to extract the saturated hydrocarbon mineral oil in the reaction solution, concentrate it and then analyze it by GC-FID.

[0045] The concentrated sulfuric acid direct sulfonation method is as follows: take 0.5 g of sample into a 10 mL glass nitrogen blowpipe, add 2 mL of n-hexane to dissolve it, then add concentrated sulfuric acid dropwise, and keep shaking during the addition process until the n-hexane layer is colorless and transparent. After standing and stratifying, take 1 mL of supernatant, add it to a disposable syringe containing 1 g of 33% acidic silica gel, squeeze it out with a push rod, and analyze it by GC-FID.

[0046] The alumina silica gel combined with sulfuric acid silica gel method is as follows: 5 g of basic alumina is added to the purification column of Example 1, and the rest of the test is carried out according to the method of Example 1.

[0047] The method of combining silver nitrate silica gel with sulfuric acid silica gel is as follows: 2 g of 10% silver nitrate silica gel is added to the purification column of Example 1, and the rest is tested according to the method of Example 1.

[0048] Table 2 Comparison of different purification methods Purification methods Verify the results Oil alkaline hydrolysis-n-hexane extraction method <![CDATA[The hydrolysis reaction rate is slow without heating. Heating will cause loss of saturated hydrocarbons with low carbon numbers. The loss of saturated hydrocarbons extracted by n-hexane from the ethanol system is relatively large, resulting in a loss of more than 50% for both C 10 -C 12 . It is difficult to apply to the situation where the sample is contaminated by kerosene.]]> Direct sulfonation with concentrated sulfuric acid <![CDATA[Partial polar impurities cannot be completely removed by n-hexane-sulfuric acid liquid-liquid partition, resulting in relatively messy spectral peaks, especially in the C 10 -C 14 region, affecting the limit of quantitation and hindering the identification of kerosene and diesel oil pollution.]]> Alumina silica gel combined with sulfuric acid silica gel method Some normal alkanes are adsorbed by alumina, which will have a certain impact on traceability and identification. Although the spectrum is relatively clean, when calculating the content of saturated hydrocarbon mineral oil, the normal alkanes on the spectrum, as sharp peaks, will be deducted and not included in the total amount. Therefore, there is no better way for quantitative analysis. Silver nitrate silica gel combined with sulfuric acid silica gel method There was no significant difference between the results of silica gel without and with silver nitrate, and silica gel with sulfuric acid alone was sufficient to remove impurities. Table 3 Comparison of conditions based on Example 1 Purification conditions Verify the results Sulfuric acid concentration 40% There will be a situation similar to carbonization, and adsorption will occur. Sulfuric acid concentration 23% The fat processing capacity is poor and the purification is incomplete. The purification column does not contain a mixture of 2 g of anhydrous sodium sulfate and 33% sulfuric acid silica gel. A large amount of samples reacted directly with 33% sulfuric acid silica gel to generate a large amount of reddish-brown substances insoluble in n-hexane that were adsorbed on the silica gel, causing a certain degree of blockage, affecting the elution degree and column efficiency. The ratio of 33% sulfuric acid silica gel to edible oil is 30:1 Increasing the ratio will not only increase the waste of filler, but also result in more n-hexane being wasted for elution. Ratio of n-hexane to 33% sulfuric acid silica gel If the elution volume is reduced to 15 mL, high-carbon saturated hydrocarbons will remain in the purification column, affecting the accuracy of the results. If the elution volume is excessively increased to 50 mL, it will not only fail to improve the accuracy of the test, but also have the following three disadvantages: eluting some unnecessary impurities, resulting in increased potential spectral interference; causing waste of reagents and increasing column time; increasing the amount of reagents will lead to longer concentration time, increasing the risk of loss during the concentration process. Pre-treatment of plastic products <![CDATA[Resulting in C 14 Previously, there were many miscellaneous peaks, so all glass products were used in subsequent optimizations]]> 3.2 Comparison of different concentration methods 3.2.1 Optimization of rotary evaporation concentration parameters The rotary evaporation concentration test of normal alkane standard was carried out to obtain C 10 The concentration parameters are determined based on the loss of 10 -C 40 The standard solution was diluted to 30 mL, and the C 10 -C 40 The content was 5 μg / mL, and the samples were concentrated using a rotary evaporator and tested on an instrument.

[0049] The endpoint pressure was set to 330 hPa, and the water bath temperatures were set to 35℃, 40℃ and 45℃, respectively. The GC-FID analysis results showed that the recoveries of C10 were 97%, 96% and 64%, respectively. The concentration times at 35℃ and 40℃ were both over 60 min, and the concentration time at 45℃ was 25 min.

[0050] The water bath temperature was set to 40℃, and the endpoint pressures were set to 330 hPa, 300 hPa and 270 hPa, respectively. The recoveries of C10 were 96%, 96% and 85%, respectively. The recoveries at 330 hPa and 300 hPa were similar but the concentration times exceeded 60 min. The concentration time at 270 hPa was 20 min but the recovery was low.

[0051] As can be seen from Table 4, when the end point pressure is lower than 300 hPa, or the water bath temperature is higher than 40°C, the loss of C10 is large. If the pressure is further increased or the temperature is lowered, there is almost no effect on the recovery, but the concentration time will be significantly increased. Therefore, the end point pressure of 300 hPa and the water bath temperature of 40°C were finally selected, and this concentration parameter was used for the detection method of this application, which significantly reduced the loss of the characteristic peak of mineral oil and ensured that the detection method can be well used for the traceability analysis of mineral oil in edible oil.

[0052] Table 4 Sample name <![CDATA[C 10 Recovery rate]]> Concentrated time 330 hPa-35℃ 97% >60 min 330 hPa-40℃ 96% >60 min 330 hPa-45℃ 64% 25 min 330 hPa-40℃ 96% >60 min 300 hPa-40℃ 96% >60 min 270 hPa-40℃ 85% 20min 3.2.2 Comparison of concentration methods after concentration to 500 μL Method 1: Directly continuing rotary evaporation concentration under the optimal concentration conditions in 3.2.1 takes a lot of time (>60 min) and is difficult to apply to daily large-scale sample testing.

[0053] Method 2: After concentrating to 500 μL, slowly blow nitrogen to less than 100 μL at room temperature (20-25°C). The whole process takes about 20 minutes, and the traceability analysis of mineral oil in edible oil can be quickly performed.

[0054] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for detecting residual mineral oil in edible oil, characterized in that: The following steps are included: 1) Extraction: Weigh edible oil and dissolve it to obtain an extract containing mineral oil; 2) Purification: transferring the extract obtained in step 1) to a purification column, and eluting the purification column to obtain an eluate; 3) Concentration: The eluate collected in step 2) is concentrated by rotary evaporation under the conditions of an end point pressure of not less than 300 hPa and a water bath temperature of not more than 40°C. When the eluate is concentrated to less than 1 mL, nitrogen is blown at room temperature to obtain a concentrated solution; 4) Detection: The concentrated solution obtained in step 3) is detected by gas chromatography-hydrogen flame ionization detector to obtain a spectrum; 5) Analysis: Conduct source analysis of mineral oil and quantitative analysis of saturated hydrocarbon mineral oil based on the spectrum obtained in step 4); Wherein, the purification column comprises sulfuric acid silica gel.

2. The method for detecting residual mineral oil in edible oil according to claim 1, characterized in that: The ratio of the sulfuric acid silica gel to the eluent is 1 g:3 mL.

3. The method for detecting residual mineral oil in edible oil according to claim 1, characterized in that: The mass ratio of the sulfuric acid silica gel to the edible oil is 20:

1.

4. The method for detecting residual mineral oil in edible oil according to claim 1, characterized in that: The purification column comprises, from bottom to top, glass wool, anhydrous sodium sulfate, neutral silica gel, silica gel sulfate, a mixture of equal mass, and anhydrous sodium sulfate.

5. The method for detecting residual mineral oil in edible oil according to claim 4, characterized in that: The mixture of equal weight consists of anhydrous sodium sulfate and silica gel sulfate.

6. The method for detecting residual mineral oil in edible oil according to claim 5, characterized in that: The sulfuric acid content of the sulfuric acid silica gel is 33%.

7. The method for detecting residual mineral oil in edible oil according to claim 1, characterized in that: When eluting the purification column in step 2), the flow rate is controlled to be 2 mL / min.

8. The method for detecting residual mineral oil in edible oil according to claim 1, characterized in that: The material of the vessel used in steps 1) to 3) is glass.

9. The method for detecting residual mineral oil in edible oil according to claim 1, characterized in that: The end point pressure in step 3) is 330 hPa and the water bath temperature is 40°C.

10. A method for detecting residual mineral oil in edible oil according to any one of claims 1 to 9, characterized in that: The mineral oil in the traceability analysis in step 5) is selected from kerosene, diesel or liquid paraffin.

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