A method for online purification, separation and preparation of saturated hydrocarbon mineral oils and aromatic hydrocarbon mineral oils

Abstract

The application provides a method for online purification, separation and preparation of saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil. The method comprises three steps of pre-experiment, sample pretreatment and preparation of liquid phase preparation, and saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil in the sample can be separated and prepared simultaneously. The method avoids the tediousness and difficulty of manual offline operation, and also makes up for many limitations of existing combined instruments. Users can flexibly adjust the separation and preparation strategy according to specific analysis requirements, and the method is convenient and simple in steps. The application is suitable for purification, separation and preparation of saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil in various food, medicine, cosmetics and petrochemical products, and can be applied to subsequent qualitative and quantitative analysis of related samples.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of analytical technology, and relates to a method for online purification, separation and preparation of saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil. BACKGROUND

[0002] Mineral oil contaminants are ubiquitous in food, drugs and cosmetics. Mineral oil is mainly derived from petroleum, and a small amount from industrial synthetic oil. Petroleum is refined into various products for human production and life, such as diesel, lubricating oil, white oil, etc. These products migrate into food, drugs and cosmetics through various ways such as raw material planting, harvesting, transportation, processing, packaging and environmental pollution, and finally enter the human body.

[0003] The chemical composition of mineral oil is very complex, containing different structural types of hydrocarbons, mainly alkanes and highly alkylated naphthenes and aromatic hydrocarbons, among which alkanes and naphthenes are collectively referred to as alkanes or saturated hydrocarbon mineral oil (MOSH), and those containing benzene rings (usually 1-5) are collectively referred to as aromatic hydrocarbon mineral oil (MOAH). The European Food Safety Authority stipulates that the carbon number range of mineral oil in food is n-C 10 ~ n-C 50 Therefore, the number of compounds involved in mineral oil is huge, including tens of thousands of structural types and their isomers.

[0004] The existing toxicology data of mineral oil is not perfect, but the existing research data shows that mineral oil is low to moderate toxicity, which poses a risk to human health. In addition, mineral oil is the largest cumulative pollutant in the human body, mainly through food intake. Among them, MOSH is easy to accumulate in the body, leading to granuloma and chronic inflammation in organs such as lymph nodes, spleen and liver, and MOAH has genetic toxicity and carcinogenicity. Therefore, MOSH and MOAH in various foods are of great concern, and MOSH and MOAH in drugs and some possible oral cosmetics (such as lipsticks and lipsticks) are also given corresponding attention.

[0005] As the analysis target, mineral oil involves tens of thousands of compounds; the chemical composition of mineral oil from different sources is also different, so it is difficult to find a corresponding standard reference material, and only the total amount can be determined. At present, the hydrogen flame ionization detector (FID) is the ideal detector for mineral oil, because the response of FID to all hydrocarbons is almost completely consistent, without the need to find a standard reference material, only to select a suitable internal standard for quantitative determination. FID is usually used with gas chromatography (GC), considering that mineral oil is generally volatile, GC-FID has become a recognized method for detecting mineral oil. However, FID is a general detector, lacking selectivity, and can only detect the total amount of MOSH and MOAH, or MOSH and MOAH are separated in advance by using a silica gel column in an offline state, and then the content of MOSH and MOAH is measured respectively, but the requirement for the experimenter is high in the offline state, the steps are complicated, pollution is easily introduced, the accuracy is difficult to control, the sample size is limited, the separated MOSH and MOAH are less, the detection limit is high, the whole process is low in efficiency, and time-consuming.

[0006] To solve the defects of offline methods, foreign countries have developed highly automated online combined instruments, that is, high performance liquid chromatography (HPLC) equipped with a silica gel column is combined with GC-FID, referred to as HPLC-GC. Through HPLC, the purification and separation of mineral oil are realized, and then the complete separation of MOSH and MOAH is completed through the interface between HPLC and GC. The advantage of the combined instrument is high automation, high running efficiency and good result reproducibility. However, the combined instrument also has an important defect, that is, the interface between HPLC and GC limits the column capacity of HPLC. Usually, the combined instrument can only use a chromatographic column with an inner diameter of 2.1 mm, and at most 20 μg of mineral oil can be separated each time. When the total amount of mineral oil exceeds 20 μg, the combined instrument cannot completely separate MOSH and MOAH, so that MOSH and MOAH cannot be accurately quantified. Therefore, in order to completely separate MOSH and MOAH, the sample is diluted before being loaded into the instrument. However, the content of MOSH in most samples is hundreds or even thousands of times that of MOAH. After the sample is diluted, the MOAH cannot reach the detection limit of the instrument. This disadvantage is particularly obvious when analyzing samples with very high MOSH content, such as liquid paraffin and vaseline hand cream. Moreover, the instrument is expensive, complex, difficult to operate, and has many influencing factors, and requires experienced experimental personnel in the field of analytical chemistry. The combined instrument is difficult to popularize, and only a few laboratories in the world have it. Some laboratories have equipped the equipment, but due to problems with the instrument itself and experimental personnel, the instrument cannot be operated normally. In summary, the combined instrument has made up for some of the defects of offline methods, but the amount of mineral oil separated each time cannot be higher than 20 μg, and the column capacity problem greatly limits the detection and analysis of mineral oil, especially MOAH, in many samples. Moreover, the high price and complex operation of HPLC-GC have led to the fact that the world has not been able to widely and deeply carry out research on mineral oil pollution and collect data, and relevant standards and regulations have not been introduced.

[0007] In summary, the key steps for analyzing mineral oil at present are purification and separation, which are mainly realized by two ways, one is the manual offline method with complex operation and poor reproducibility, and the other is the highly automated HPLC-GC combined instrument. However, both methods have their own defects, which have caused the slow development of mineral oil analysis and testing technology, and have not been able to provide technical support for market supervision and relevant standards and policies. SUMMARY

[0008] In order to improve the shortcomings of the existing analysis technology, the present application provides a method for online purification, separation and preparation of saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil. Through pre-experiment, the total amount of mineral oil in the sample is preliminarily quantified by GC-FID. Then, the sample is pretreated to preliminarily purify and separate the mineral oil in the sample, and the pretreatment process can remove the triglyceride, natural olefin and other matrix interference substances that may be contained in the sample and affect the quantification of the mineral oil. Finally, according to the total amount of the mineral oil in the sample obtained by the pre-experiment, the sample is appropriately diluted if necessary, and MOSH and MOAH in the sample are separated and prepared by the preparation liquid phase online separation and preparation technology. The method of the present application can realize the separation and preparation of MOSH and MOAH in different matrices such as food, cosmetics, petrochemical products and drugs.

[0009] The specific technical scheme of the present application is:

[0010] A method for online purification, separation and preparation of saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil, the method comprising the following steps:

[0011] (1) adding anhydrous ethanol to the sample to be tested, ultrasonic, then adding potassium hydroxide aqueous solution, mixing, heating and shaking, cooling, then adding n-hexane, shaking again, centrifuging to obtain supernatant, and concentrating the supernatant;

[0012] (2) adding m-chloroperbenzoic acid ethanol solution to the concentrated supernatant, shaking, adding ethanol and sodium thiosulfate aqueous solution, shaking, centrifuging, and collecting the upper n-hexane phase;

[0013] (3) equilibrating a silica gel column with dichloromethane-n-hexane mixed solution, then passing the collected upper n-hexane phase through the silica gel column, and eluting the silica gel column with dichloromethane-n-hexane mixed solution, collecting the effluent, and concentrating to obtain the pretreated sample to be separated;

[0014] (4) passing the pretreated sample to be separated through a preparation column to separate saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil, and eluting with n-hexane and dichloromethane as mobile phase, and collecting saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil respectively.

[0015] According to the embodiment of the present application, the method can realize online purification, separation and preparation of MOSH and MOAH in different matrices such as food, cosmetics, petrochemical products and drugs.

[0016] According to the embodiment of the present application, the sample to be tested comprises at least one of food, cosmetics, petrochemical products and drugs.

[0017] According to the embodiment of the present application, the purpose of step (1) is to remove triglyceride substances in the sample by saponification.

[0018] According to an embodiment of the present application, in step (1), the temperature of the heating and shaking is 50-80℃, for example 60℃, and the time of the heating and shaking is 30-120min, for example 50-60min.

[0019] According to an embodiment of the present application, in step (1), the concentration of the aqueous potassium hydroxide solution is 5-8mol / L, for example 6mol / L or 7mol / L.

[0020] According to an embodiment of the present application, in step (1), the mass-volume ratio of the sample to be tested and the anhydrous ethanol is 0.5g:(5-10)mL.

[0021] According to an embodiment of the present application, in step (1), the mass-volume ratio of the sample to be tested and the n-hexane is 0.5g:(20-40)mL.

[0022] According to an embodiment of the present application, in step (1), the n-hexane is added in batches, which can improve the extraction rate of MOSH and MOAH.

[0023] For example, after cooling, a portion of n-hexane is added, and the mixture is shaken again. After centrifugation, the supernatant is collected. A portion of n-hexane is added to the bottom material, and the mixture is shaken again. After centrifugation, the supernatant is collected. The supernatants collected after multiple centrifugations are mixed and concentrated.

[0024] According to an embodiment of the present application, in step (1), the volume of the concentrated supernatant is 0.5-1.5mL.

[0025] According to an embodiment of the present application, in step (1), an internal standard can also be added to test the content of the prepared MOSH and MOAH. The type and amount of the internal standard can be selected and adjusted according to the instrument used to test MOSH and MOAH.

[0026] According to an embodiment of the present application, the purpose of step (2) is to remove olefinic substances in the sample by epoxidation.

[0027] According to an embodiment of the present application, in step (2), the concentration of the m-chloroperbenzoic acid ethanol solution is 150mg / mL-300mg / mL. That is, 150mg-300mg of m-chloroperbenzoic acid is added to 1mL of ethanol solution.

[0028] According to an embodiment of the present application, in step (2), the concentration of the aqueous sodium thiosulfate solution is 50g / L-200g / L, that is, 50g-200g of sodium thiosulfate is added to 1L of water.

[0029] According to an embodiment of the present application, in step (2), the mass-volume ratio of the sample to be tested and the m-chloroperbenzoic acid-ethanol solution is 0.5g:(0.5-1)mL.

[0030] According to an embodiment of the present application, in step (2), the mass-volume ratio of the sample to be tested and the ethanol is 0.5g:(0.5-1)mL.

[0031] According to an embodiment of the present application, in step (2), the mass-volume ratio of the sample to be tested and the sodium thiosulfate aqueous solution is 0.5g:(1-5)mL.

[0032] According to an embodiment of the present application, in step (1) and step (2), the frequency of the shaking (plate circumferential operation) is not particularly limited, and is a routine operation in the art, and exemplarily, the frequency of the shaking is 300rpm-800rpm, and the time of the shaking is also not particularly limited, and is, for example, 1min or more, as long as the solution is uniformly mixed.

[0033] According to an embodiment of the present application, in step (2), the number of revolutions of the centrifugation is not particularly limited, and is a routine operation in the art, and exemplarily, the number of revolutions of the centrifugation is 3000rpm-4000rpm, and the time of the centrifugation is also not particularly limited, and is, for example, 1min or more.

[0034] According to an embodiment of the present application, the purpose of step (3) is to remove polar substances and a small amount of impurities that are not soluble in n-hexane from the sample.

[0035] According to an embodiment of the present application, in step (3), the silica gel column is filled with active silica gel, and the filling amount of the active silica gel is 2-3g.

[0036] According to an embodiment of the present application, in step (3), before the collection of the effluent, a step of discarding a dead volume is further included. The dead volume is, for example, 1-2mL.

[0037] According to an embodiment of the present application, in step (3), the dichloromethane-n-hexane mixed solution is, for example, a mixed solution of 20%-40% dichloromethane and 60%-80% n-hexane, and exemplarily, a mixed solution of 20% dichloromethane and 80% n-hexane.

[0038] According to an embodiment of the present application, in step (3), the volume after the concentration is 0.5-1.5mL.

[0039] According to an embodiment of the present application, in step (4), the preparation column is selected from a silica gel filled chromatographic column capable of separating MOSH and MOAH, and is, for example, selected from Dalian ELLUT Si60, with a particle size of 5μm and a length×inner diameter of 250mm×10mm.

[0040] According to an embodiment of the present application, in step (4), the separation can achieve separation of 2000 μg MOSH and MOAH at one time.

[0041] According to an embodiment of the present application, in step (4), the elution with the mobile phase of n-hexane and dichloromethane comprises the following steps:

[0042] When the elution time is 0-3 min, the mobile phase comprises n-hexane and dichloromethane, and the volume percentage of n-hexane gradually decreases from 100% to 70%, and the volume percentage of dichloromethane gradually increases from 0% to 30%;

[0043] When the elution time is 3-7 min, the mobile phase comprises n-hexane and dichloromethane, and the volume percentage of n-hexane is 70%, and the volume percentage of dichloromethane is 30%;

[0044] When the elution time is 7-10 min, the mobile phase comprises n-hexane and dichloromethane, and the volume percentage of n-hexane gradually decreases from 70% to 0%, and the volume percentage of dichloromethane gradually increases from 30% to 100%;

[0045] When the elution time is 10-30 min, the mobile phase comprises dichloromethane, and the volume percentage of dichloromethane is 100%;

[0046] When the elution time is 30-35 min, the mobile phase comprises n-hexane and dichloromethane, and the volume percentage of n-hexane gradually increases from 0% to 100%, and the volume percentage of dichloromethane gradually decreases from 100% to 0%;

[0047] When the elution time is 35-55 min, the mobile phase comprises n-hexane, and the volume percentage of n-hexane is 100%.

[0048] According to an embodiment of the present application, in step (4), the injection volume of the pretreated sample to be separated is 0.5-1 mL.

[0049] According to an embodiment of the present application, in step (4), the flow rate of the mobile phase is 2-4 mL / min, for example, 3 mL / min.

[0050] According to an embodiment of the present application, in step (4), the components collected at 4 min-7 min are MOSH, and the components collected at 8 min-15 min are MOAH.

[0051] According to an embodiment of the present application, the method further comprises the following steps:

[0052] (5) Concentrating the collected MOSH and MOAH respectively, to realize online purification, separation and preparation of MOSH and MOAH.

[0053] According to an embodiment of the present application, the method further comprises the following steps:

[0054] (3') diluting the pretreated sample to be separated and then passing through a preparation column to separate MOSH and MOAH.

[0055] According to an embodiment of the present application, in step (3'), the purpose of dilution is to prevent the preparation column from being overloaded and the separation of MOSH and MOAH from being unable to be achieved due to the total amount of mineral oil in the sample to be separated being too high.

[0056] According to an embodiment of the present application, in step (3'), the dilution factor is different according to the total amount of mineral oil (MOSH and MOAH) in the sample to be separated.

[0057] For example, the pretreated sample to be separated is diluted by A / 16000 times and then passed through a preparation column to separate MOSH and MOAH, wherein A is the total amount of mineral oil in the sample, in mg / kg.

[0058] If A cannot be divided by 16000, the integer part is taken, and if A / 16000 is less than 1, no dilution is needed and the sample is directly injected, wherein A is the total amount of mineral oil in the sample, in mg / kg.

[0059] According to an embodiment of the present application, step (4) is repeated multiple times to achieve a large amount of preparation of MOSH and MOAH (2000 μg of MOSH and MOAH is separated and prepared at one time). Specifically, the number of times of repetition can be determined according to the sensitivity of the analysis instrument used for subsequent quantitative and qualitative analysis of the prepared MOSH and MOAH.

[0060] According to an embodiment of the present application, the method further comprises a pre-experiment process, which comprises the following steps:

[0061] (a) mixing the sample to be separated, n-hexane and an internal standard, ultrasonicating, oscillating, centrifuging, collecting the supernatant, concentrating to obtain a concentrated solution;

[0062] (b) equilibrating a silica gel column with a dichloromethane-n-hexane mixed solution, then passing the concentrated solution of step (a) through the silica gel column and eluting the silica gel column with the dichloromethane-n-hexane mixed solution, collecting the effluent, and concentrating and taking the supernatant;

[0063] (c) detecting the supernatant of step (b) by GC-FID to obtain the total amount of mineral oil in the sample.

[0064] According to an embodiment of the present application, in step (a), the internal standard is cyclohexylcyclohexane (Cycy) and amylbenzene (5B).

[0065] According to the embodiment of the present application, in step (a), the mass-volume ratio of the sample to be separated and n-hexane is 0.2 g:(5-20) mL.

[0066] According to the embodiment of the present application, in step (a), the mass ratio of the sample to be separated and the internal standard is 0.2 g:(15-30) μg.

[0067] According to the embodiment of the present application, in step (a), the volume of the concentrated sample is 0.5-1.5 mL.

[0068] According to the embodiment of the present application, in step (b), the silica gel column is filled with active silica gel, and the filling amount of the active silica gel is 2-3 g.

[0069] According to the embodiment of the present application, in step (b), the dichloromethane-n-hexane mixed solution is, for example, a mixed solution of 20%-40% dichloromethane and 60%-80% n-hexane, and exemplarily a mixed solution of 20% dichloromethane and 80% n-hexane.

[0070] According to the embodiment of the present application, in step (c), the GC-FID detection condition is: DB-1 HT, 15 m x 0.25 mm x 0.10 μm; carrier gas: nitrogen; carrier gas flow rate: 22.8 mL / min; injection volume: 1.0 μL; injection port temperature: 360°C; temperature rising program: initial temperature of 60°C, keeping for 3 min, linearly rising to 120°C at a rate of 15°C / min, then linearly rising to 360°C at a rate of 25°C / min, keeping for 6 min; injection mode: splitless.

[0071] According to the embodiment of the present application, in step (c), one of the internal standards with small matrix effect on peak area is selected to quantitate the bump peak of mineral oil, so as to obtain the total amount A of mineral oil in the sample.

[0072] According to the embodiment of the present application, the calculation formula of the total amount A of mineral oil in the sample is as follows:

[0073]

[0074] A - total amount of mineral oil in the sample, mg / kg;

[0075] As - peak area of the bump peak of mineral oil in the sample;

[0076] Ap - peak area of the sharp peak of mineral oil in the sample;

[0077] Ai - peak area of the internal standard;

[0078] mi - internal standard addition amount, μg; mi = 20 μg;

[0079] m - sample weighing amount, g.

[0080] According to the embodiment of the present application, the method comprises the following steps:

[0081] The pre-experiment process is as follows: 0.2 g of sample is weighed into a glass centrifugal tube, 10 mL of n-hexane is added, 20 μg of Cycy and 5B two kinds of internal standards are added respectively, ultrasonic is performed for 30 min, oscillation is performed at 60°C for 5 min, sedimentation is performed at 4°C for 20 min, centrifugation is performed at 3500 rpm for 10 min, all supernatant is transferred to a chicken heart bottle, rotary evaporation is performed at 40°C to about 1 mL; 2 g of activated silica gel is loaded into a glass column with an inner diameter of 1.3 cm, the column is knocked, the column is first balanced with 5 mL of 20% dichloromethane-80% n-hexane mixed solution, all concentrated liquid is loaded, 11 mL of 20% dichloromethane-80% n-hexane mixed solution is eluted, then the eluent is concentrated to 1 mL by rotary evaporation at 40°C, centrifugation is performed at 3500 rpm for 10 min, the supernatant is taken and loaded into a sample vial, and GC-FID detection is performed; the GC-FID detection conditions are as follows: DB-1HT, 15 m x 0.25 mm x 0.10 μm; carrier gas: nitrogen; carrier gas flow rate: 22.8 mL / min; sample injection volume: 1.0 μL; sample injection port temperature: 360°C; temperature rising program: initial temperature of 60°C, keeping for 3 min, linearly rising to 120°C at a rate of 15°C / min, then linearly rising to 360°C at a rate of 25°C / min, keeping for 6 min; sample injection mode: no split; one of the two internal standards with small matrix influence on the peak area is selected to quantitatively determine the bulging peak of mineral oil, and the total amount of mineral oil in the sample is A.

[0082]

[0083] A - total amount of mineral oil in the sample, mg / kg;

[0084] As - peak area of the bulging peak of mineral oil in the sample;

[0085] Ap - peak area of the sharp peak of mineral oil in the sample;

[0086] Ai - peak area of the internal standard;

[0087] mi - internal standard addition amount, μg; mi = 20 μg;

[0088] m - sample weighing amount, g.

[0089] The sample pretreatment process is as follows: 0.5 g of sample is weighed into a glass centrifuge bottle, 5 mL of anhydrous ethanol is added, vortexed thoroughly, ultrasonically treated for 10 min, 5 mL of 6 mol / L potassium hydroxide aqueous solution is added, mixed, shaken at 60°C for 50 min, after cooling, 10 mL of n-hexane is added, shaken at 350 rpm for 15 min, centrifuged at 3500 rpm for 15 min, the supernatant is taken into a glass centrifuge bottle, 10 mL of n-hexane is added into the glass centrifuge tube, shaken at 350 rpm for 15 min, centrifuged at 3500 rpm for 15 min, the supernatants of the two times are combined into the glass centrifuge bottle, the supernatant is concentrated to about 1 mL, and then transferred into a 15 mL glass centrifuge tube; 500 μL of 200 mg / mL m-chloroperbenzoic acid-ethanol solution is added into the centrifuge tube, the centrifuge tube is placed in a constant-temperature shaking metal bath, shaken at 500 rpm for 20 min at 40°C, 0.5 mL of ethanol and 2 mL of 100 g / L sodium thiosulfate-water solution are added into the centrifuge tube, shaken at 750 rpm for 1 min, centrifuged at 3500 rpm for 6 min, and the whole supernatant n-hexane phase is transferred into a 15 mL centrifuge tube; 2 g of activated silica gel is loaded into a glass column with an inner diameter of 1.3 cm, the column is knocked, 5 mL of 20% dichloromethane-80% n-hexane mixed solution is used to balance the column, then the whole sample solution is transferred to the silica gel column, the sample solution is dried, 11 mL of 20% dichloromethane-80% n-hexane is used to elute the column, 1 mL of dead volume is discarded, the remaining liquid is collected into a glass centrifuge bottle, the sample solution is concentrated to about 1 mL, and then the concentrated solution is transferred into a 2 mL volumetric flask, diluted to the mark, and mixed.

[0090] The preparation liquid preparation process is as follows: the sample solution obtained in the sample pretreatment process is diluted by 16000 times, when A cannot be divided by 16000, the integer part is taken, when A / 16000 is less than 1, no dilution is needed, and the sample is directly injected, the injection volume is 0.5 mL, the flow rate is 3 mL / min, the preparation column is a Si60 5 μm 250 mm*10 mm from Dalian Elite, the mobile phase A is n-hexane, the mobile phase B is dichloromethane, the gradient elution ratio is as follows: 0-3 min, the mobile phase A is 100%→70%; 3-7 min, the mobile phase A is 70%; 7-10 min, the mobile phase A is 70%→0%; 10-30 min, the mobile phase A is 0; 30-35 min, the mobile phase A is 0%→100%; 35-55 min, the mobile phase A is 100%, the 4-7 min component is collected as the MOSH component, the 8-15 min component is collected as the MOAH component, and the preparation cycle number is C times; finally, the MOSH and MOAH components obtained by C times of preparation are concentrated to about 1 mL at 40°C by rotary evaporation, and the C value is determined according to the sensitivity of the analysis instrument used for subsequent quantitative and qualitative analysis of the MOSH and MOAH components.

[0091] Beneficial effects:

[0092] The application provides a method for online purification, separation and preparation of saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil, and the pretreatment process provided by the method can effectively remove interfering substances of mineral oil in food, cosmetics, petrochemical products and medicines, such as natural olefins and triglycerides, and simultaneously efficiently separates and prepares MOSH and MOAH in food, cosmetics, petrochemical products and medicines, and 2000ug of MOSH and MOAH can be separated and prepared at one time, and the MOSH and MOAH can be prepared for multiple cycles according to needs, so that the current situation that only 20ug of MOSH and MOAH can be separated by the existing HPLC-GC technology is greatly improved. Meanwhile, the MOSH and MOAH prepared by the method can be applied to various analysis and detection instruments such as GC-FID, comprehensive two-dimensional gas chromatography-mass spectrometry, ultraviolet-visible spectrum analysis, fluorescence spectrum analysis and infrared spectrum analysis. The application separates and prepares MOSH and MOAH in samples by using preparative liquid phase online, avoids offline cumbersome and difficult manual operation, and can get rid of problems such as high price and complex operation caused by HPLC-GC, and the method is simple, has strong universality and is easy to popularize. Users can flexibly adjust the scheme according to specific experimental needs, the preparation method of the application is suitable for different sample matrices such as food, cosmetics, medicines and petrochemical products, the unified pretreatment step improves the applicability of the method, and is helpful for research and detection analysis of mineral oil by detection institutions, scientific research units and production enterprises. BRIEF DESCRIPTION OF DRAWINGS

[0093] Figure 1 The MOSH component GC-FID spectrum diagram of the standard industrial oil prepared by the preparative liquid phase in the embodiment 1 of the application;

[0094] Figure 2 The MOAH component GC-FID spectrum diagram of the standard industrial oil prepared by the preparative liquid phase in the embodiment 1 of the application;

[0095] Figure 3 The mineral oil bump peak GC-FID chromatogram of the lipstick in the embodiment 2 of the application;

[0096] Figure 4 The mineral oil sharp peak GC-FID chromatogram of the lipstick in the embodiment 2 of the application;

[0097] Figure 5 The preparative liquid phase ultraviolet spectrum diagram and MOSH and MOAH component outflow schematic diagram in the embodiment 2 of the application;

[0098] Figure 6 The MOSH component LC-GC spectrum diagram of the mineral oil of the lipstick prepared by the preparative liquid phase in the embodiment 2 of the application;

[0099] Figure 7LC-GC chromatogram of MOAH component after preparation, separation of mineral oil in lipstick in Example 2 of the present application;

[0100] Figure 8 GCxGC-TOF chromatogram of MOSH component in lipstick in Example 3 of the present application. DETAILED DESCRIPTION

[0101] The present application will be further described in conjunction with specific examples. It should be understood that the following examples are only illustrative and explanatory of the present application, and should not be interpreted as limiting the scope of the present application. Any technology realized based on the above description of the present application is encompassed in the scope of the present application.

[0102] The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0103] Example 1

[0104] Investigation of recovery rate of MOSH and MOAH after preparation of standard industrial oil by preparative liquid chromatography

[0105] 1. Materials and methods

[0106] 1.1 Standard industrial oil

[0107] The standard industrial oil provided in this example is prepared by a series of steps such as solution, column passing, dilution, constant volume, etc. from the industrial lubricating grease used in the laboratory, and is detected by a professional third-party detection laboratory. The MOSH content in the standard industrial oil is 4.59 mg / mL, and the MOAH content is 2.56 mg / mL.

[0108] 1.2 Experimental methods

[0109] Three parallel samples and one blank sample were prepared to investigate the recovery rate of MOSH and MOAH after preparation of standard industrial oil by preparative liquid chromatography.

[0110] 1.2.1 Sample pretreatment

[0111] Into a glass centrifuge bottle, pipette 1.0 mL of the above standard industrial oil, add 5 mL of absolute ethanol, vortex well, sonicate for 10 min, add 5 mL of 6 M aqueous potassium hydroxide, add 200 μL of 100 μg / mL of the 5B, 2-methylnaphthalene (2-MN), 1-methylnaphthalene (1-MN), 1,3,5-tri-tert-butylbenzene (TBB), 1,4-di(2- ethylhexyl)benzene (DEHB), Cycy, and n-undecane (C11) mixture, add 300 μL of 100 μg / mL each of the perylene (Per) and cholestane (Cho) single standards, add 100 μL of 100 μg / mL n-tridecane (C13), vortex well, and shake at 60°C for 50 min. After cooling, add 10 mL of n-hexane, shake at 350 rpm for 15 min, centrifuge at 3500 rpm for 15 min, pipette the supernatant into a glass centrifuge bottle, add 10 mL of n-hexane to the glass centrifuge tube, shake at 350 rpm for 15 min, centrifuge at 3500 rpm for 15 min, combine the two supernatants in the glass centrifuge bottle, concentrate the supernatant to about 1 mL by rotary evaporation at 40°C, and transfer the concentrate to a 15 mL glass centrifuge tube. Add 500 μL of 200 mg / mL of m-chloroperoxybenzoic acid in ethanol to the centrifuge tube, place the tube in a constant temperature shaking metal bath, and shake at 500 rpm for 20 min at 40°C. Add 0.5 mL of ethanol and 2 mL of 100 g / L sodium thiosulfate in water to the centrifuge tube, shake at 750 rpm for 1 min, centrifuge at 3500 rpm for 6 min, and transfer the entire supernatant to a 15 mL centrifuge tube. Pack 2 g of activated silica gel into a glass column with an inner diameter of 1.3 cm, tap the column, equilibrate the column with 5 mL of 20% dichloromethane in 80% n-hexane, then transfer the entire sample solution to the column, and concentrate the sample solution to about 1 mL by rotary evaporation at 40°C. Transfer the concentrate to a 2 mL volumetric flask, dilute to volume, and mix well.

[0112] 1.3 Preparation of the liquid separation preparation

[0113] The sample solution obtained in the sample pretreatment process was loaded into a sample bottle and prepared by preparative liquid chromatography. Equipment: high-performance semi-preparative liquid chromatograph brave pl700, equipped with a UV detector, preparative column: Dalian Yilite Si60 5 μm 250 mm x 10 mm, sample volume 0.5 mL, flow rate 3.0 mL / min, mobile phase A: n-hexane, mobile phase B: dichloromethane, gradient elution ratio: 0-3 min, mobile phase A: 100%→70%; 3-7 min, mobile phase A: 70%; 7-10 min, mobile phase A: 70%→0%; 10-30 min, mobile phase A: 0%; 30-35 min, mobile phase A: 0%→100%; 35-55 min; mobile phase A: 100%, collect the 4-7 min component as MOSH component, and collect the 8 min-15 min component as MOAH; the MOSH and MOAH components prepared by preparative liquid chromatography were concentrated to about 1 mL by rotary evaporation at 40°C.

[0114] 1.4 GC-FID detection analysis

[0115] The MOSH and MOAH components obtained by preparative liquid chromatography were loaded into a sample vial and detected by GC-FID; the GC-FID detection conditions were as follows: DB-1HT, 15 m x 0.25 mm x 0.10 μm; carrier gas: nitrogen; carrier gas flow rate: 22.8 mL / min; sample volume: 1.0 μL; sample port temperature: 360°C; temperature rising program: initial temperature 60°C, hold for 3 min, linearly increase the temperature to 120°C at a rate of 15°C / min, then linearly increase the temperature to 360°C at a rate of 25°C / min, hold for 6 min; sample injection mode: splitless.

[0116] 2 Experimental results

[0117] The MOSH and MOAH components were detected by GC-FID, the MOSH component was quantified by selecting Cycy as the internal standard, and the MOAH component was quantified by selecting 2-MN as the internal standard, and then the recovery rates of MOSH and MOAH after preparative liquid chromatography of the sample were calculated, and the results are shown in Table 1. The GC-FID spectrum of the MOSH component after preparative liquid chromatography of the standard industrial oil is shown in Figure 1 , and the GC-FID spectrum of the MOAH component after preparative liquid chromatography of the standard industrial oil is shown in Figure 2 .

[0118] Table 1 Recovery rates of MOSH and MOAH after preparative liquid chromatography of the standard industrial oil

[0119]

[0120] According to the quantitative results of GC-FID, the recovery rate of MOSH component is 92.0%-97.0%, the recovery rate of MOAH component is 102.2%-108.9%, and MOSH and MOAH are not detected in the sample blank, indicating that the method for on-line purification, separation and preparation of MOSH and MOAH has good recovery rate.

[0121] Example 2

[0122] Determination of MOSH and MOAH content in lipstick

[0123] 1 Experimental method

[0124] 1.1 Pre-experiment

[0125] 1.1.1 Pre-experiment steps

[0126] 0.2 g of lipstick sample was weighed into a glass centrifuge tube, 10 mL of n-hexane was added, 20 μg of Cycy and 5B two kinds of internal standards were added respectively, ultrasonic was performed for 30 min, oscillation was performed at 60℃ for 5 min, sedimentation was performed at 4℃ for 20 min, centrifugation was performed at 3500 rpm for 10 min, all supernatant was transferred to a chicken heart bottle, rotary evaporation was performed at 40℃ to about 1 mL; 2 g of activated silica gel was loaded into a glass column with an inner diameter of 1.3 cm, the column was knocked, the column was first balanced with 5 mL of 20% dichloromethane-80% n-hexane mixed solution, all the concentrated liquid was loaded, 11 mL of 20% dichloromethane-80% n-hexane mixed solution was used for elution, then the eluent was concentrated to 1 mL at 40℃, centrifugation was performed at 3500 rpm for 10 min, the supernatant was taken and loaded into a sample vial, and GC-FID detection was performed; the GC-FID detection conditions were as follows: DB-1HT, 15 m x 0.25 mm x 0.10 μm; carrier gas: nitrogen; carrier gas flow rate: 22.8 mL / min; sample injection volume: 1.0 μL; sample injection port temperature: 360℃; temperature rising program: initial temperature of 60℃, keeping for 3 min, linearly rising to 120℃ at a rate of 15℃ / min, then linearly rising to 360℃ at a rate of 25℃ / min, keeping for 6 min; sample injection mode: no split.

[0127] 1.1.2 Pre-experiment results

[0128] Because the peak area of the internal standard Cycy is less affected by the matrix, the mineral oil in the sample was quantified with Cycy as the internal standard, and the result was 1.64 x 10 5 mg / kg. The GC-FID chromatogram of the mineral oil bump peak in the lipstick is shown in Figure 3 , and the GC-FID chromatogram of the mineral oil sharp peak in the lipstick is shown in Figure 4 .

[0129] 1.2 Sample pretreatment

[0130] Weigh 0.5g of lipstick sample into a glass centrifuge bottle, add 5mL of anhydrous ethanol, vortex thoroughly, sonicate for 10min, then add 5mL of 6mol / L potassium hydroxide aqueous solution, 25μL of a 100μg / mL mixed standard of 5B, 2-MN, 1-MN, TBB, and DEHB, 15μL of 10mg / mL Cho and C13 single standards, 30μL of 10mg / mL Cycy and C11 single standards, and 10μL of 200μg / mL [unclear - possibly a specific concentration of ethanol]. Mix the peroxide by vortexing and incubate at 60°C for 50 min. After cooling, add 10 mL of n-hexane, incubate at 350 rpm for 15 min, and centrifuge at 3500 rpm for 15 min. Transfer the supernatant to a pistol flask, add another 10 mL of n-hexane to a glass centrifuge tube, incubate at 350 rpm for 15 min, and centrifuge at 3500 rpm for 15 min. Combine the two supernatants in the pistol flask and concentrate the supernatant to approximately 1 mL by rotary evaporation at 40°C. Transfer the supernatant to a 15 mL glass centrifuge tube. Add 500 μL of 200 mg / mL m-chloroperoxybenzoic acid-ethanol solution to the centrifuge tube. Place the centrifuge tube in a constant-temperature shaking metal bath and incubate at 40°C with shaking at 500 rpm for 20 min. Then centrifuge... Add 0.5 mL of ethanol and 2 mL of 100 g / L sodium thiosulfate aqueous solution to the tube, shake at 750 rpm for 1 min, centrifuge at 3500 rpm for 6 min, and transfer the entire upper hexane phase to a 15 mL centrifuge tube; pack 2 g of activated silica gel into a 1.3 cm inner diameter glass column, tap the column firmly, first equilibrate the column with 5 mL of a 20% dichloromethane-80% hexane mixed solution, then transfer the entire sample solution to the chromatography column. When the sample solution is nearly dry, wash the chromatography column with 11 mL of 20% dichloromethane-80% hexane, discard 1 mL of dead volume, collect the remaining liquid into a pistol flask, and concentrate the sample solution to about 1 mL by rotary evaporation at 40 °C. Transfer the concentrate to a 2 mL volumetric flask, make up to volume, and mix well.

[0131] 1.3 Preparation of Liquid-Phase Separation

[0132] Take 0.5 mL of the sample solution obtained from the sample pretreatment process into a 5 mL volumetric flask, dilute to volume with n-hexane, mix well, and transfer to a sample vial for preparative liquid chromatography. Equipment: Brave PL700 high-performance semi-preparative liquid chromatograph with UV detector; preparative column: Dalian Elite Si60 5μm 250mm×10mm; injection volume: 0.5mL; flow rate: 3.0mL / min; mobile phase A: n-hexane; mobile phase B: dichloromethane; gradient elution ratio: 0-3min, mobile phase A 100%→70%; 3-7min, mobile phase A 70%; 7-10min, mobile phase A 70%→0%; 10-30min, mobile phase A 0%; 30-35min, mobile phase A 0%→100%; 35-55min, mobile phase A 100%; collect the fraction collected at 4-7min as MOSH fraction, and collect the fraction collected at 8-15min as MOAH fraction; concentrate the obtained MOSH and MOAH fractions separately by rotary evaporation at 40℃ to approximately 1mL. The MOAH fraction was directly loaded into a vial and quantitatively detected by LC-GC; the MOSH fraction was transferred to a 2 mL volumetric flask, diluted to volume with n-hexane, mixed well, and then diluted 40 times before quantitative detection by LC-GC.

[0133] 1.4 LC-GC Detection Conditions

[0134] LC conditions: injection volume 50 μL, Allure Si column (250 mm × 2.1 mm, 5 μm), (Restek Corporation, USA); the mobile phase was a mixture of n-hexane and dichloromethane, eluted with a gradient at 0.3 mL / min. The elution program was: 0-1.5 min n-hexane, 1.6-6.2 min 70% n-hexane + 30% dichloromethane; after all MOSH (2.0-3.5 min) and MOAH (4.5-6.0 min) in the test solution had eluted, the LC was backflushed to regenerate the column, with dichloromethane backflushed at a flow rate of 0.5 mL / min for 6.3-15.2 min. The mobile phase changes and MOSH / MOAH elution during the LC run were monitored using a UV detector (230 nm).

[0135] LC-GC interface: After LC purification and separation, 450 μL of MOSH and MOAH were obtained, respectively. The two fractions were directed to GC analysis by valve switching (VIGI AG, Switzerland) with hydrogen as carrier gas. The GC instrument was equipped with two parallel channels consisting of a pre-column (Restek MXT uncoated capillary pre-column, 10 m x 0.53 mm) and an analytical column (Restek MXT capillary column, 15 m x 0.25 mm x 0.25 μm). MOSH and MOAH entered one channel each, and the pre-column was connected to a solvent vent valve with a tee between the pre-column and the analytical column. The solvent vent valve was opened 0.5 min before the LC fraction valve switched and closed 0.3 min after the switching was finished. Most of the solvent in MOSH and MOAH transferred to the GC system was removed by the solvent vent valve, and the remaining small amount of solvent was concentrated with the solutes at the inlet of the analytical column for subsequent GC separation and determination.

[0136] GC conditions: programmed temperature, initial temperature 60 °C, hold for 6 min, increase to 120 °C at 15 °C / min, then increase to 370 °C at 25 °C / min, hold for 6 min. FID temperature was 380 °C; auxiliary gas, combustion gas and carrier gas were nitrogen, hydrogen and air, respectively, with flow rates of 30, 40 and 400 mL / min.

[0137] 2 Experimental results

[0138] The sample solution was prepared and separated by preparative liquid chromatography to obtain MOSH and MOAH components. The preparative liquid chromatography UV spectrum and the MOSH and MOAH component flow-out schematic diagram are shown in Figure 5 . The prepared MOSH and MOAH were quantitatively analyzed by LC-GC. The MOSH component was quantified in the sample with Cycy as an internal standard, and the result was 1.4 x 10 5 mg / kg; the MOAH component was quantified in the sample with 2-MN as an internal standard, and the result was 1.2 x 10 3 mg / kg. The MOSH component LC-GC spectrum after the mineral oil in the lipstick was prepared and separated by preparative liquid chromatography is shown in Figure 6 , and the MOAH component LC-GC spectrum after the mineral oil in the lipstick was prepared and separated by preparative liquid chromatography is shown in Figure 7 .

[0139] Example 3

[0140] Qualitative analysis of MOSH in lipstick by comprehensive two-dimensional gas chromatography-time of flight mass spectrometry

[0141] 1 Experimental method

[0142] 1.1 Pre-experiment

[0143] 1.1.1 Pre-experiment steps

[0144] Take 0.2 g lipstick sample into a glass centrifuge tube, add 10 mL n-hexane, add 20 μg Cycy and 5B two kinds of internal standard, ultrasonic 30 min, 60℃ oscillation 5 min, 4℃ sedimentation 20 min, 3500 rpm centrifugation 10 min, transfer all supernatant to a chicken heart bottle, 40℃ rotary evaporation to about 1 mL; 2 g activated silica gel is loaded into a glass column with 1.3 cm inner diameter, knock the column, the column is first balanced with 5 mL 20% dichloromethane-80% n-hexane mixed solution, all concentrated liquid is loaded, eluted with 11 mL 20% dichloromethane-80% n-hexane mixed solution, then the eluent is concentrated to 1 mL at 40℃, centrifuged at 3500 rpm for 10 min, take the supernatant, load into a sample vial, GC-FID detection; GC-FID detection conditions: DB-1HT, 15 m x 0.25 mm x 0.10 μm; carrier gas: nitrogen; carrier gas flow rate: 22.8 mL / min; injection volume: 1.0 μL; injection port temperature: 360℃; temperature program: initial temperature 60℃, hold for 3 min, linearly increase to 120℃ at a rate of 15℃ / min, then linearly increase to 360℃ at a rate of 25℃ / min, hold for 6 min; injection mode: no split.

[0145] 1.1.2 Pre-experiment results

[0146] The internal standard Cycy peak area is less affected by the matrix, take Cycy as the internal standard, the mineral oil in the sample is quantified, the result is 1.64 x 10 5 mg / kg.

[0147] 1.2 Sample pretreatment

[0148] Take 0.5 g lipstick sample into a glass centrifuge bottle, add 5 mL absolute ethanol, vortex well, ultrasonic for 10 min, then add 5 mL 6 mol / L potassium hydroxide aqueous solution, add 25 μL of 100 μg / mL 5B, 2-MN, -MN, TBB, DEHB mixed label, add 15 μL of 10 mg / ml Cho, C13 single label, add 30 μL of 10 mg / ml Cycy and C11 single label, add 10 μL of 200 μg / mL Per, vortex well, shake at 60°C for 50 min, after cooling, add 10 mL n-hexane, shake at 350 rpm for 15 min, centrifuge at 3500 rpm for 15 min, take the supernatant into a glass centrifuge tube, add 10 mL n-hexane, shake at 350 rpm for 15 min, centrifuge at 3500 rpm for 15 min, combine the two supernatants into a glass centrifuge tube, concentrate the supernatant to about 1 mL at 40°C, transfer to a 15 mL glass centrifuge tube; add 500 μL of 200 mg / mL m-chloroperbenzoic acid-ethanol solution to the centrifuge tube, place the centrifuge tube in a constant temperature shaking metal bath, shake at 500 rpm for 20 min at 40°C, then add 0.5 mL of ethanol and 2 mL of 100 g / L sodium thiosulfate-aqueous solution to the centrifuge tube, shake at 750 rpm for 1 min, centrifuge at 3500 rpm for 6 min, transfer all the n-hexane phase to a 15 mL centrifuge tube; pack 2 g of activated silica gel into a glass column with an inner diameter of 1.3 cm, knock the column, first equilibrate the column with 5 mL of 20% dichloromethane-80% n-hexane mixed solution, then transfer all the sample solution to the column, when the sample solution is almost dry, elute the column with 11 mL of 20% dichloromethane-80% n-hexane, discard 1 mL of dead volume, collect the remaining liquid into a glass centrifuge tube, concentrate the sample solution to about 1 mL at 40°C, transfer the concentrated solution to a 2 mL volumetric flask, dilute to volume, mix well.

[0149] 1.3 Preparation of liquid separation preparation treatment

[0150] The sample solution obtained in the pretreatment process was taken into a 5 mL volumetric flask, diluted with n-hexane, mixed, loaded into an injection bottle, and prepared by preparative liquid chromatography. Equipment: high-performance semi-preparative liquid chromatograph brave pl700 with a UV detector, preparative column: Dalian Yili Si60 5 μm 250 mm x 10 mm, injection volume: 0.5 mL, flow rate: 3.0 mL / min, mobile phase A: n-hexane, mobile phase B: dichloromethane, gradient elution ratio: 0-3 min, mobile phase A: 100%→70%; 3-7 min, mobile phase A: 70%; 7-10 min, mobile phase A: 70%→0; 10-30 min, mobile phase A: 0; 30-35 min, mobile phase A: 0-100%; 35-55 min; mobile phase A: 100%, the component collected at 4-7 min was MOSH component, and the preparative cycle was repeated 3 times; the MOSH component prepared was concentrated to about 1 mL by rotary evaporation at 40°C.

[0151] 1.4 GCxGC-TOF qualitative analysis

[0152] 1 μL of the MOSH component was taken and manually injected into GCxGC-TOF.

[0153] The GCxGC-TOF detection conditions were as follows:

[0154] 1.4.1 Instrument model: gas phase: A91 Plus (Changzhou Pannuo Instruments Co., Ltd.); mass spectrometry: EI-TOFMS 0620 (Guangzhou Huxin Instruments Co., Ltd.); solid-state modulator: SSM 1810 solid-state modulator (Xuexing Electronic Technology (Shanghai) Co., Ltd.);

[0155] 1.4.2 Gas phase conditions: one-dimensional chromatographic column DB-17HT (20 m x 0.25 mm i.d. x 0.15 μm df, Agilent Technologies), two-dimensional chromatographic column DB-1MS (1.5 m x 0.25 mm i.d. x 0.10 μm df, Agilent Technologies), injection port temperature: 330°C; injection amount: 1 μL; 1:5 split injection; carrier gas: helium; column flow rate: 1.7 mL / min; programmed temperature: initial temperature 50°C, hold for 3 min, increase to 335°C at 5°C / min.

[0156] 1.4.3 Modulator conditions: solid-state thermal modulator, DV modulation column (1.1 m x 0.25 mm i.d.), cycle 9 s, thermal desorption time 1 s. Cold zone temperature settings: initial temperature 9 °C, ramp to -51 °C at -50 °C / min, hold for 21.8 min, then ramp to 9 °C at 20 °C / min, hold for 34 min; initial temperature of hot zone inlet 50 °C, hold for 3 min, ramp to 330 °C at 5 °C / min, hold for 1 min; initial temperature of hot zone outlet 50 °C, hold for 3 min, ramp to 330 °C at 5 °C / min, hold for 1 min.

[0157] 1.4.4 Time-of-flight mass spectrometer conditions: electron impact source; detector voltage: -164 V; ionization voltage -70 V; ion source temperature 250 °C; GC-MS transfer line (0.195 m, i.e. 2D column); interface temperature 320 °C; acquisition mass range 50-650 m / z; acquisition speed 101 spectra / s; solvent delay 2.6 min.

[0158] 1.4.5 Data processing method: mass spectral data acquisition was performed using the acquisition and control software of the time-of-flight mass spectrometer, and two-dimensional data were processed and analyzed using the Canvas full two-dimensional chromatogram data processing software (V1.8, J&X Technologies, Shanghai, China).

[0159] 2 Experimental results

[0160] The MOSH components of the lipstick were detected and analyzed by GCxGC-TOF. The MOSH in the lipstick included n-alkanes, iso-alkanes and cycloalkanes. The GCxGC-TOF spectrum of the MOSH components in the lipstick is shown in Figure 8 .

[0161] The above describes embodiments of the present application. However, the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for online purification, separation and preparation of saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil, comprising the following steps: (1) adding anhydrous ethanol to a sample to be tested, ultrasonicating, then adding an aqueous solution of potassium hydroxide, mixing, heating and shaking, adding n-hexane after cooling, shaking again, centrifuging to obtain supernatant, and concentrating the supernatant; (2) adding an m-chloroperoxybenzoic acid ethanol solution to the concentrated supernatant, shaking, adding an ethanol and sodium thiosulfate aqueous solution, shaking, centrifuging, and collecting the upper n-hexane phase; (3) equilibrating a silica gel column with a dichloromethane-n-hexane mixed solution, then passing the collected upper n-hexane phase through the silica gel column, and eluting the silica gel column with a dichloromethane-n-hexane mixed solution, collecting the effluent, and concentrating to obtain a pretreated sample to be separated; (4) passing the pretreated sample to be separated through a preparation column to separate saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil, and eluting with n-hexane and dichloromethane as mobile phases, and collecting saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil, respectively; the method further comprises the following step: (3') diluting the pretreated sample to be separated by A / 16000 times, wherein A is the total amount of mineral oil in the sample, and passing the diluted sample through the preparation column to separate MOSH and MOAH, wherein A / 16000 is an integer; if A cannot be divided by 16000, the integer part is taken; if A / 16000 is less than 1, the sample does not need to be diluted; the method further comprises a pre-experiment process, which comprises the following steps: (a) mixing the sample to be separated, n-hexane and an internal standard, ultrasonicating, shaking, centrifuging, collecting supernatant, and concentrating to obtain a concentrated solution; (b) equilibrating a silica gel column with a dichloromethane-n-hexane mixed solution, then passing the concentrated solution of step (a) through the silica gel column, and eluting the silica gel column with a dichloromethane-n-hexane mixed solution, collecting the effluent, and concentrating to obtain supernatant; (c) detecting the supernatant of step (b) by GC-FID to obtain the total amount of mineral oil in the sample; in step (1), the concentration of the aqueous solution of potassium hydroxide is 5-8 mol / L; and / or, in step (1), the mass-volume ratio of the sample to be tested to anhydrous ethanol is 0.5 g:(5-10) mL; and / or, in step (1), the mass-volume ratio of the sample to be tested to n-hexane is 0.5 g:(20-40) mL; and / or, in step (2), the concentration of the m-chloroperoxybenzoic acid ethanol solution is 150 mg / mL-300 mg / mL; and / or, in step (2), the concentration of the sodium thiosulfate aqueous solution is 50 g / L-200 g / L; and / or, in step (2), the mass-volume ratio of the sample to be tested to the m-chloroperoxybenzoic acid-ethanol solution is 0.5 g:(0.5-1) mL; and / or, in step (2), the mass-volume ratio of the sample to be tested to the sodium thiosulfate aqueous solution is 0.5 g:(1-5) mL; in step (3), the dichloromethane-n-hexane mixed solution is a mixed solution of 20%-40% dichloromethane and 60%-80% n-hexane. ​ ​ ​ ​ ​ ​ wherein ​ ​ ​ ​ ​ 2. The method of claim 1, wherein, ​ ​ ​ ​ ​ ​ ​ 3. The method of claim 1, wherein, ​ And / or, in step (4), the preparation column is selected from silica gel packed chromatographic column capable of separating saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil; And / or, in step (4), the separation can separate 2000 μg of saturated hydrocarbon mineral oil and aromatic hydrocarbon mineral oil at one time.

4. The method according to any one of claims 1 to 3, wherein, In step (4), elution with n-hexane and dichloromethane as mobile phase includes the following steps: When the elution time is 0-3 min, the mobile phase includes n-hexane and dichloromethane, and the volume fraction of n-hexane gradually decreases from 100% to 70%, and the volume fraction of dichloromethane gradually increases from 0% to 30%; When the elution time is 3-7 min, the mobile phase includes n-hexane and dichloromethane, and the volume fraction of n-hexane is 70%, and the volume fraction of dichloromethane is 30%; When the elution time is 7-10 min, the mobile phase includes n-hexane and dichloromethane, and the volume fraction of n-hexane gradually decreases from 70% to 0%, and the volume fraction of dichloromethane gradually increases from 30% to 100%; When the elution time is 10-30 min, the mobile phase includes dichloromethane, and the volume fraction of dichloromethane is 100%; When the elution time is 30-35 min, the mobile phase includes n-hexane and dichloromethane, and the volume fraction of n-hexane gradually increases from 0% to 100%, and the volume fraction of dichloromethane gradually decreases from 100% to 0%; When the elution time is 35-55 min, the mobile phase includes n-hexane, and the volume fraction of n-hexane is 100%.

5. The method according to any one of claims 1-3, wherein, In step (4), the components collected at 4-7 min are MOSH, and the components collected at 8-15 min are MOAH.

6. The method of claim 1, wherein, In step (a), the internal standard is cyclohexyl cyclohexane and amyl benzene; And / or, in step (a), the mass-volume ratio of the sample to be separated and n-hexane is 0.2 g:(5-20) mL; And / or, in step (a), the mass ratio of the sample to be separated and the internal standard is 0.2 g:(15-30) μg; And / or, in step (a), the volume after concentration is 0.5-1.5 mL; And / or, in step (b), the silica gel column is filled with active silica gel, and the filling amount of the active silica gel is 2-3 g; And / or, in step (b), the dichloromethane-n-hexane mixed solution is a mixed solution of 20%-40% dichloromethane and 60%-80% n-hexane.

7. The method of any one of claims 1-3, wherein, The method includes the following steps: The pre-experiment process is: taking 0.2 g sample into a glass centrifugal tube, adding 10 mL n-hexane, adding 20 μg of cyclohexyl cyclohexane and pentyl benzene two kinds of internal standards respectively, ultrasonic for 30 min, 60℃ oscillation for 5 min, 4℃ sedimentation for 20 min, 3500 rpm centrifugation for 10 min, transferring all supernatant to a chicken heart bottle, 40℃ rotary evaporation to about 1 mL; 2 g of activated silica gel is loaded into a glass column with an inner diameter of 1.3 cm, knock the column, first use 5 mL of 20% dichloromethane-80% n-hexane mixed solution to balance the column, all concentrated liquid is loaded, 11 mL of 20% dichloromethane-80% n-hexane mixed solution is used for elution, then the eluent is concentrated to 1 mL at 40℃, 3500 rpm centrifugation for 10 min, take the supernatant, load into a sample vial, GC-FID detection; GC-FID detection conditions are: DB-1HT, 15 m x 0.25 mm x 0.10 μm; carrier gas: nitrogen; carrier gas flow rate: 22.8 mL / min; injection volume: 1.0 μL; injection port temperature: 360℃; temperature program: initial temperature of 60℃, holding for 3 min, linearly increasing to 120℃ at a rate of 15℃ / min, then linearly increasing to 360℃ at a rate of 25℃ / min, holding for 6 min; injection mode: splitless; select one of the two internal standards with small matrix influence on the peak area to quantify the bulge peak of mineral oil, and the total amount of mineral oil in the sample is A ; A = A— Total amount of mineral oil in the sample, mg / kg; As - Peak area of mineral oil bleb in sample; Ap— Mineral oil spike peak area in sample; Ai - peak area of internal standard; mi - amount of internal standard added, pg; mi = 20 pg; m—sample weight, g; The sample pretreatment process is as follows: 0.5 g of sample is weighed into a glass centrifuge bottle, 5 mL of anhydrous ethanol is added, vortexed thoroughly, ultrasonically treated for 10 min, 5 mL of 6 mol / L potassium hydroxide aqueous solution is added, mixed, shaken at 60°C for 50 min, after cooling, 10 mL of n-hexane is added, shaken at 350 rpm for 15 min, centrifuged at 3500 rpm for 15 min, the supernatant is taken into a glass centrifuge bottle, 10 mL of n-hexane is added into the glass centrifuge tube, shaken at 350 rpm for 15 min, centrifuged at 3500 rpm for 15 min, the supernatants of the two times are combined into the glass centrifuge bottle, the supernatant is concentrated to about 1 mL, and then transferred into a 15 mL glass centrifuge tube; 500 μL of 200 mg / mL m-chloroperbenzoic acid-ethanol solution is added into the centrifuge tube, the centrifuge tube is placed in a constant-temperature shaking metal bath, shaken at 500 rpm for 20 min at 40°C, 0.5 mL of ethanol and 2 mL of 100 g / L sodium thiosulfate-water solution are added into the centrifuge tube, shaken at 750 rpm for 1 min, centrifuged at 3500 rpm for 6 min, and the whole supernatant n-hexane phase is transferred into a 15 mL centrifuge tube; 2 g of activated silica gel is loaded into a glass column with an inner diameter of 1.3 cm, the column is tapped, 5 mL of 20% dichloromethane-80% n-hexane mixed solution is used to balance the column, then the whole sample solution is transferred to the silica gel column, the sample solution is dried, 11 mL of 20% dichloromethane-80% n-hexane is used to elute the column, 1 mL of dead volume is discarded, the remaining liquid is collected into a glass centrifuge bottle, the sample solution is concentrated to about 1 mL, and then the concentrated solution is transferred into a 2 mL volumetric flask, diluted to the mark, and mixed well; The preparation liquid preparation process is as follows: the sample solution obtained in the sample pretreatment process is diluted by 16000 times, when A cannot be divided by 16000, the integer part is taken, when A / 16000 is less than 1, no dilution is needed, and the sample is directly injected, the injection volume is 0.5 mL, the flow rate is 3 mL / min, the preparation column is a Si60 5 μm 250 mm*10 mm column from Dalian Elite, the mobile phase A is n-hexane, the mobile phase B is dichloromethane, the gradient elution ratio is as follows: 0-3 min, the mobile phase A is 100%→70%; 3-7 min, the mobile phase A is 70%; 7-10 min, the mobile phase A is 70%→0%; 10-30 min, the mobile phase A is 0; 30-35 min, the mobile phase A is 0%→100%; 35-55 min, the mobile phase A is 100%, the 4-7 min component is collected as the MOSH component, the 8-15 min component is collected as the MOAH component, and the cycle preparation number is C times; finally, the MOSH and MOAH components obtained by C times of preparation are concentrated to about 1 mL by rotary evaporation at 40°C, and the C value is determined according to the sensitivity of the analysis instrument used for subsequent quantitative and qualitative analysis of the MOSH and MOAH components.

Images