A sunflower oil matrix standard sample containing 3-chloropropanol ester and preparation method thereof

Abstract

The present invention relates to the technical field of food detection, and in particular to a sunflower oil matrix standard sample containing 3-MCPD and a preparation method thereof. Sodium chloride, water, zinc chloride and other substances are added to sunflower oil, fully heated and stirred, frozen centrifuged to remove water, chloride ions are removed by anion exchange resin, zinc ions are removed by cation exchange resin, and antioxidants are added to ensure the stability of 3-MCPD. The matrix standard sample prepared by the present invention has undergone strict homogeneity and stability tests, and has the advantages of good uniformity and high stability.

Description

Technical Field

[0001] The invention relates to the technical field of food detection, and in particular to a sunflower seed oil matrix standard sample containing 3-chloropropanol ester (3-MCPD ester) and a preparation method thereof. Background Art

[0002] Chloropropanol (RIM) is the esterification product of chloropropanol compounds and fatty acids. According to the different types of chloropropanol, it can be divided into 3-chloropropanol ester (3-MCPD ester), 2-chloro-1,3-propanediol ester (2-MCPD ester), 1,3-dichloro-2-propanol ester (1,3-DCP ester) and 2,3-dichloro-2-propanol ester (2,3-DCP ester). The 3-chloropropanol ester is detected in the highest amount in food. Recent studies have found that 3-chloropropanol ester is detected in cereals, coffee, fish, meat products, potatoes, nuts and heat-processed oil foods with vegetable oil as raw materials. In particular, the reports of 3-chloropropanol ester detected in refined vegetable oil and other foods are gradually increasing. There are many studies on the source and formation mechanism of 3-MCPD in edible vegetable oil at home and abroad. High temperature treatment during oil production is one of the main reasons for the increase in 3-MCPD content in oil.

[0003] MCPD is potentially carcinogenic, mainly causing damage to the kidneys, testicles and ovaries, affecting sperm activity and causing fertility disorders. The human intestine has the possibility of hydrolyzing 3-MCPD. It has many hazards to human health, including kidney toxicity, reproductive toxicity, neurotoxicity, immunotoxicity, carcinogenicity and genotoxicity. Therefore, controlling and reducing the content of chloropropanol in food is an important measure to ensure food safety.

[0004] In recent years, my country has been the largest producer and consumer of food, grain and oil. Its total grain and oil output has always ranked first in the world, and its per capita share has greatly exceeded the world average. However, its development speed cannot keep up with the rapid growth of oil and fat consumption. In order to meet the needs of supply and development of China's edible oil market, the amount of oil and fat imported by China has remained high in the past decade. my country attaches great importance to food safety, and edible vegetable oil is closely related to people's life and health. To this end, "safety" and "quality" must always be put first. In order to control the quality of grain and oil products, it is very necessary to detect chloropropanol in grain and oil.

[0005] The quality control method currently used in the test is to add a high-purity chloropropanol standard substance to the edible oil sample for detection and analysis, but this method cannot reflect the enrichment state of chloropropanol in the edible oil, and the preparation and addition of chloropropanol standards vary according to the techniques of different testers, and the accuracy of the detection method cannot be guaranteed. Therefore, it is necessary to develop a chloropropanol standard sample based on sunflower oil as a quality control method for detecting chloropropanol in the sunflower oil to be tested. Summary of the invention

[0006] The invention aims to provide a sunflower seed oil matrix standard sample containing 3-chloropropanol ester (3-MCPD ester) and a preparation method thereof.

[0007] In order to achieve the above objectives, the technical solution adopted by the present invention is as follows: a sunflower oil matrix standard sample containing 3-chloropropanol ester is prepared by:

[0008] Step 1, taking sunflower seed oil, adding 0.2%-2.0% sodium chloride, 5-15% water and 1.0-6.0 mg / kg zinc chloride according to the weight of the oil, stirring and treating at 160-200° C. for 2-4 hours to obtain a first oil sample; % refers to the mass ratio of a certain substance to the weight of sunflower seed oil; mg / kg refers to the number of milligrams of a certain substance added to each kilogram of sunflower seed oil;

[0009] Step 2, cooling the first oil sample, performing refrigerated centrifugation, discarding the water layer, and obtaining a second oil sample;

[0010] Step 3: Take the second oil sample, add 5-15% anion exchange resin and 0.5-1.5% cation exchange resin according to the weight of the oil, stir at 50-70°C for 2-4h, and filter to obtain the third oil sample;

[0011] Step 4: Add 0.2-4.0 mg / kg of antioxidant to the third oil sample according to the weight of the oil, stir at 50-70° C. for 1-3 h, and mix thoroughly to obtain a fourth oil sample;

[0012] Step 5: Centrifuge the fourth oil sample to obtain a sunflower oil matrix standard sample containing 3-chloropropanol ester.

[0013] The amount of the anion exchange resin and the cation exchange resin is sufficient to completely adsorb and remove chloride ions and zinc ions. In step 3, the anion exchange resin and the cation exchange resin are removed by filtration.

[0014] When less than 0.2% sodium chloride and less than 1.0 mg / kg zinc chloride are added based on the oil weight, or more than 2% sodium chloride and more than 6.0 mg / kg zinc chloride are added based on the oil weight, the homogeneity of the finally prepared sunflower oil matrix standard sample containing 3-chloropropanediol ester (3-MCPD ester) decreases.

[0015] In a preferred embodiment, in step three, the cations include zinc ions. In step one, 1.0% sodium chloride and 3.0 mg / kg zinc chloride are added according to the weight of the oil. The sunflower oil matrix standard sample containing 3-chloropropanol ester obtained in step five is stored in a dark and refrigerated state. In step three, 10% of a strongly basic anion exchange resin and 1% of a strongly acidic cation exchange resin are added according to the weight of the oil, stirred at 60°C for 3h, and after completion, filtered to obtain a third oil sample. In step four, 2.0 mg / kg of TBHQ antioxidant is added to the third oil sample according to the weight of the oil, and mixed thoroughly.

[0016] During use, the strong acid cation exchange resin will adsorb impurities and release strong acid groups to exchange with all cations in the oil, and zinc ions and sodium ions will be removed. Strong base anion exchange resin and strong acid anion exchange resin have different affinities for different ions in the solution and are selective in their adsorption, so they can be used at the same time.

[0017] The present invention also provides a method for preparing a sunflower oil matrix standard sample containing 3-chloropropanol ester, comprising the following steps:

[0018] Step 1: Take sunflower oil, add 0.2%-2.0% sodium chloride, 5-15% water and 1.0-6.0 mg / kg zinc chloride according to the weight of the oil, stir and treat at 160-200° C. for 2-4 hours to obtain a first oil sample;

[0019] Step 2, cooling the first oil sample, performing refrigerated centrifugation, discarding the water layer, and obtaining a second oil sample;

[0020] Step 3: Take the second oil sample, add 5-15% anion exchange resin and 0.5-1.5% cation exchange resin according to the weight of the oil, stir at 50-70°C for 2-4h, and filter to obtain the third oil sample;

[0021] Step 4: Add 0.2-4.0 mg / kg of antioxidant to the third oil sample according to the weight of the oil, stir at 50-70° C. for 1-3 h, and mix thoroughly to obtain a fourth oil sample;

[0022] Step 5: Centrifuge the fourth oil sample to obtain a sunflower oil matrix standard sample containing 3-chloropropanol ester.

[0023] In step 1, sodium chloride, water and zinc chloride are added and reacted at a certain temperature to promote the generation of 3-chloropropanol ester (3-MCPD) in sunflower oil and make it stable for a long time in sunflower oil. In the present invention, it is found that chloride ions and zinc ions have a relatively large effect on the uniformity of the matrix standard sample, so chloride ions and zinc ions are removed by step 3. The reason why the present invention adds the antioxidant last is to prevent the inhibition of the generation of 3-MCPD and improve the short-term and long-term stability of the sunflower oil matrix standard sample containing 3-chloropropanol ester.

[0024] In step 2, the role of frozen centrifugation is to remove moisture. If frozen centrifugation is not performed, it will have a significant impact on uniformity and stability, which will manifest as oil-water stratification after long-term storage.

[0025] In step 1, the mixture is stirred at 160-200℃ for 2-4h and the speed is 200-400r / min; in step 3, the mixture is stirred at 50-70℃ for 1-3h and the speed is 200-400r / min; in step 4, the mixture is stirred at 50-70℃ for 1-3h and the speed is 200-400r / min; the temperature, speed and mixing time also have a great influence on the uniformity and stability. In step 1, the temperature of 160-200℃ is conducive to the production of 3-MCPD, and the speed and time are important parameters for considering the uniformity of the sample when preparing the matrix standard sample. If the speed is low or the time is short, the reaction is not sufficient, which affects the uniformity of the target substance data of the matrix sample. In steps 3 and 4, the temperature is selected to be 50-70℃ to minimize the change of 3-MCPD as much as possible, while also taking into account the temperature of the reaction of the anion exchange resin and the cation exchange resin in the oil system; if the speed is low or the time is short, the reaction or mixing is not sufficient and cannot be completely removed, which affects the uniformity and stability of the target substance data of the matrix sample.

[0026] The present invention is beneficial in that:

[0027] 1. The present invention provides a method for preparing a 3-MCPD matrix standard sample in sunflower seed oil, by adding sodium chloride (the main purpose is to introduce chloride ions), water, zinc chloride (the main purpose is to introduce zinc ions) and other substances into the sunflower seed oil, fully heating and stirring, freezing and centrifuging to remove water, removing chloride ions by strong alkaline anion exchange, removing zinc ions and sodium ions by strong acid cation exchange resin, and adding antioxidants to ensure the stability of 3-MCPD. The matrix standard sample prepared by the present invention has undergone a strict uniformity test and has the advantages of good uniformity and high stability. It has been proved by inspection that this standard sample can guarantee product quality under different transportation conditions, meet the transportation requirements of different regions, and has a long shelf life. It is an effective and reliable physical standard sample that can be used for quality control in related detection and analysis fields. It can also be used as a means to certify and assess the analytical capabilities of laboratories or technicians participating in the test, and has significant economic value and market competitiveness;

[0028] In the prior art, when studying the effect of added substances on the formation of monochloropropanol esters in oils and fats, one component is used to achieve the formation of monochloropropanol esters in oils and fats. For example, Yan Peng. The effect of antioxidants on the formation of monochloropropanol esters and carbonyl compounds during the heating of palm oil [D]. Nanchang University, 2020. discloses a palm oil-sodium chloride model and a palm oil-ferric chloride model, and a single component can achieve the formation of monochloropropanol esters in oils and fats. Generally, it is preferred to add as few components as possible to the standard sample to prevent multiple components from bringing more uncertainty to the safety, uniformity and stability of the standard sample. This is different from the conclusion in the present invention. In the present invention, the matrix standard sample prepared by a single component: sodium chloride or zinc chloride has poor sample uniformity, while sodium chloride and zinc chloride can be compounded in a certain proportion according to the oil weight to obtain a standard sample with uniformity that meets the requirements.

[0029] 2. The difficulty of forming the sunflower oil matrix standard sample containing 3-MCPD is that the catalytic effect of the catalyst may be offset by the complex components in the actual grease; the low content of DAG in sunflower oil, the presence of free fatty acids and moisture inhibit the generation of 3-MCPD; the present invention adopts sodium chloride and zinc chloride as catalysts, sodium chloride and zinc chloride are compounded according to the oil weight in a certain ratio to prepare the uniformity of the sunflower oil matrix standard sample containing 3-MCPD. When only sodium chloride or zinc chloride is used, when 3-MCPD is generated in sunflower oil under heating conditions, the homogeneity of the sunflower oil matrix standard sample finally obtained does not meet the requirements. And the zinc ions or chloride ions etc. added, if retained in the sunflower oil matrix standard sample, the homogeneity of the sunflower oil matrix standard sample finally obtained does not meet the requirements, so sodium chloride and zinc chloride are compounded according to the oil weight in a certain ratio and added to sunflower oil during preparation, and after 3-MCPD is formed, the zinc ions or chloride ions etc. added need to be removed.

[0030] In the prior art, the change of chloride ion content during oil refining has an impact on the content of 3-MCPD. For example, Wang Luyang. Research on the influence of chloride ion content change during oil refining on the formation of 3-MCPD and glycidyl ester [D]. Henan University of Technology, 2018. Before high-temperature deodorization, activated carbon is used to adsorb and decolorize the oil to reduce the chloride ion content. The purpose is to reduce the content of 3-MCPD during oil refining. After deodorization, there is no need to use activated carbon for adsorption and decolorization. In the present invention, sodium chloride, zinc chloride and other substances are added to sunflower oil and heated to generate 3-MCPD in sunflower oil, and then frozen centrifuged. At this time, the temperature is relatively low, and sodium chloride, zinc chloride and other substances will not theoretically have an additional impact on the sunflower oil containing 3-MCPD, and the uniformity detection is relatively time-consuming. Sodium chloride, zinc chloride and other substances will not theoretically affect the uniformity of the standard sample. In the present invention, the opposite phenomenon is observed. The added zinc ions or chloride ions need to be removed, otherwise the uniformity of the final prepared matrix standard sample is poor.

[0031] 3. The present invention fills the blank of the lack of sunflower seed oil matrix standard samples containing 3-MCPD in my country. The standard samples of the present invention will be mainly used in laboratory capability verification, internal quality control, method verification and other activities; it is helpful for laboratory quality control to ensure the accuracy of quantitative detection results; it is helpful to strengthen the quality and safety control of sunflower seed oil production and improve the detection level of inspection and testing institutions.

[0032] 4. Uniformity is the basic property of standard substances. It is difficult to obtain standard samples with qualified uniformity for real physical standard samples due to the difficulty of preparation method, high investment, long investment time, unclear metabolic law of target components and other factors. However, the present invention determines that under the prescribed prerequisites, sample preparation is carried out by adding sodium chloride, water, zinc chloride and other substances to sunflower oil, fully heating and stirring, freezing centrifugation to remove water, strong alkaline anion exchange resin to remove chloride ions, strong acid cation exchange resin to remove cations including zinc ions, adding antioxidants and other links to change the addition amount, temperature, time and other parameters, so as to promote the production of 3-MCPD components of chloropropanol, and finally obtain better uniformity.

[0033] This preparation method directly generates 3-MCPD in sunflower oil to obtain a matrix standard sample, which can fully reflect the enrichment state of chloropropanol in sunflower oil. As a real physical standard sample, it is more accurate and reliable when used for detection.

[0034] 5. Stability is also a basic property of standard substances. Standard samples involve storage and transportation processes from preparation to use, which may cause changes in the stability of standard samples. Therefore, two aspects of stability evaluation are required. One is to select the temperature for short-term stability evaluation based on the form of sample packaging and transportation. It is usually carried out under different temperature conditions to examine the influence of temperature on the characteristic values ​​of standard substances; the other is to regularly test the characteristic values ​​of standard substances over a long period of time under specified storage conditions to examine their ability to remain within the specified range. The short-term stability and long-term stability of the matrix standard sample prepared according to the present invention meet the requirements, and the total validity period is 24 months under a storage environment of 2-8°C.

[0035] 6. The samples in Group A in Example 1 of the present invention were tested by 9 laboratories and the standard value was determined to be 0.814 mg / kg. DETAILED DESCRIPTION

[0036] The present invention is described in detail below with reference to specific embodiments.

[0037] Example 1 Preparation of sunflower oil matrix standard sample containing 3-MCPD under different process parameters

[0038] Group A: A method for preparing a sunflower oil matrix standard sample containing 3-MCPD, the specific preparation method is as follows:

[0039] Sunflower oil purchased from the market was selected, 10g of sodium chloride and 3mg of zinc chloride were fully dissolved in 100g of water to form an aqueous solution, the aqueous solution was then mixed with 1kg of sunflower oil, heated and stirred at 180℃ for 3h, the speed was 300r / min; after cooling to room temperature, it was placed in a -4℃ constant temperature box for 1h, and refrigerated centrifugation was performed at a temperature of -4℃ and a speed of 12000r / min, and the water layer was discarded; 10% of a strong basic styrene anion exchange resin (Yaoyang 201*7FD, an addition amount of 100g) was added according to the weight of the oil, and at the same time, 1% of a strong acid cation exchange resin (model: Dowex(R) 50WX4 Hydrogen Form, an addition amount of 10g) was added, stirred at 60℃ for 3h, the speed was 300r / min, and filtered; 2.0mg of TBHQ antioxidant was added, stirred at 60℃ for 2h, the speed was 300r / min, and fully mixed; 12000 The standard sample of sunflower oil matrix containing chloropropanol was obtained by centrifugation at r / min for 30 min; the sample was packaged in a brown PET plastic bottle and stored in a refrigerator at 2-8°C.

[0040] In group A, 1% sodium chloride, 10% water, 3 mg / kg zinc chloride, 10% anion exchange resin, 1% cation exchange resin, and 2 mg / kg TBHQ antioxidant were added based on the weight of the oil.

[0041] Group B: Unlike Group A, no sodium chloride was added and the amount of zinc chloride became the amount of zinc chloride + sodium chloride in Group A.

[0042] Group C: Different from Group A, zinc chloride was not added and the amount of sodium chloride became the amount of zinc chloride + sodium chloride in Group A.

[0043] Group D: Unlike Group A, no strong alkaline anion exchange resin was added during the preparation of Group D samples.

[0044] Group E: Unlike Group A, no strong acidic cation exchange resin was added during the preparation of Group E samples.

[0045] Group F: Unlike Group A, no TBHQ antioxidant was added.

[0046] Group G: Different from Group A, 3% sodium chloride and 10 mg / kg zinc chloride were added according to the weight of oil.

[0047] Example 2

[0048] Sunflower oil purchased from the market was selected, and 0.8% sodium chloride, 10% water and 5 mg / kg zinc chloride were added to the system according to the weight of the oil. The mixture was heated and stirred at 200°C for 3 h at a speed of 300 r / min. After cooling to room temperature, it was placed in a -4°C constant temperature box for 1 h, and refrigerated centrifugation was performed at a temperature of -4°C and a speed of 12000 r / min to discard the water layer. According to the weight of the oil, 5% of a strongly basic styrene anion exchange resin (Yaoyang 201*7FD) and 1% of a strongly acidic cation exchange resin (model: Dowex(R) 50WX4Hydrogen Form) were added, stirred at 60°C for 3 h at a speed of 300 r / min, and filtered. According to the weight of the oil, 2.0 mg / kg of TBHQ antioxidant was added, stirred at 60°C for 2 h at a speed of 300 r / min, and mixed thoroughly. 12000 The standard sample of sunflower oil matrix containing chloropropanol was obtained by centrifugation at r / min for 30 min; the sample was packaged in a brown PET plastic bottle and stored in a refrigerator at 2-8°C.

[0049] Example 3

[0050] Sunflower oil purchased from the market was selected, and 1.5% sodium chloride, 10% water and 2 mg / kg zinc chloride were added to the system according to the weight of the oil, and heated and stirred at 160°C for 3 hours at a speed of 300 r / min; after cooling to room temperature, it was placed in a -4°C constant temperature box for 1 hour, and refrigerated centrifugation was performed at a temperature of -4°C and a speed of 12000 r / min, and the water layer was discarded; 15% of a strongly basic styrene anion exchange resin (Yaoyang 201*7FD) and 1% of a strongly acidic cation exchange resin (model: Dowex(R) 50WX4Hydrogen Form) were added according to the weight of the oil, stirred at 60°C for 3 hours at a speed of 300 r / min, and filtered; 2.0 mg / kg of TBHQ antioxidant was added according to the weight of the oil, stirred at 60°C for 2 hours at a speed of 300 r / min, and mixed thoroughly; 12000 The standard sample of sunflower oil matrix containing chloropropanol was obtained by centrifugation at r / min for 30 min; the sample was packaged in a brown PET plastic bottle and stored in a refrigerator at 2-8°C.

[0051] Example 4 Uniformity Test

[0052] The uniformity of each group of samples in Example 1 was tested. The detection method adopted "GB 5009.191-2024 National Food Safety Standard Determination of Chloropropanol and Its Fatty Acid Esters and Glycidyl Esters in Food". The statistical method adopted the one-way variance statistical analysis method, and the three-level samples were tested for uniformity by using the F test. The specific method is to randomly select 15 bags from the samples prepared in the above groups, and each sample is tested as an independent sub-sample. Each sub-sample is also required to be tested three times in parallel, and the experimental result is the average of the parallel measurements. All samples are tested in a random order under repeatability conditions.

[0053] The test results are shown in Tables 1-7.

[0054] Table 1 A group sample uniformity evaluation measurement result record

[0055]

[0056] Table 2. Record of uniformity evaluation results of group B samples

[0057]

[0058] Table 3. C group sample uniformity evaluation measurement result record

[0059]

[0060] Table 4 D group sample uniformity evaluation measurement result record

[0061]

[0062] Table 5 E group sample uniformity evaluation measurement result record

[0063]

[0064] Table 6 F group sample uniformity evaluation measurement result record

[0065]

[0066] Table 7 G group sample uniformity evaluation measurement result record

[0067]

[0068] The above data were subjected to one-way ANOVA, and the following ANOVA results were obtained: when the confidence probability was 0.95 and the degree of freedom f 1 =14, f 2 =30, it can be concluded from the F test table that F 0.05（14，30） =2.04, the F values ​​in the samples of group B and group C are both greater than the critical value F 0.05（14，30） , indicating that the sample is not uniform. The test results of the samples in groups D and E do not meet the F test requirements, indicating that chloride ions, zinc ions, and sodium ions have a greater impact on the uniformity of the sunflower oil matrix standard sample containing 3-MCPD, and the use of ion exchange resin to remove chloride ions, zinc ions, and sodium ions is important. The F value in the sample of group G is greater than the F critical value, indicating that the sample is not uniform.

[0069] The F value of samples in group A and group F is less than the critical value F 0.05（14，30） , indicating that there were no significant differences within and between groups A and F samples, and the samples were uniform and met the requirements for being quality control samples.

[0070] Example 5 Stability Test

[0071] The samples that meet the uniformity requirements are tested for stability, and the samples in group A are selected for the experiment. According to "JJF1343-2022 General Principles and Statistical Principles for the Determination of Standard Materials", the statistical method for stability testing is determined to be the t analysis test method. The characteristic value change curve over time is used to determine whether the sample characteristic value has a unidirectional change trend, and the stability of the standard sample is evaluated by a linear fitting model. Stability testing includes two aspects: long-term stability (storage stability) and short-term stability (transportation stability). Sampling is carried out according to the principle of dense sampling first and sparse sampling later. A total of 7 sampling time points are set for short-term stability, stored at 4°C, 20°C, and 40°C, and a total of 7 sampling time points are set for long-term stability testing, stored at 2-8°C. Three samples from group A and group F are randomly selected at each sampling time point, and each sample is repeated twice. The average value of the three sub-samples is taken to analyze the content of the target in the samples of group A and group F.

[0072] Table 8 Short-term stability results of 3-MCPD esters in group A samples at 4°C

[0073]

[0074] Table 9 Short-term stability results of 3-MCPD esters in group A samples at 20°C

[0075]

[0076] Table 10 Short-term stability results of 3-MCPD esters in group A samples at 40°C

[0077]

[0078] Table 11 Long-term stability results of 3-MCPD esters in samples of group A stored at 2-8°C

[0079]

[0080] Table 12 Short-term stability results of 3-MCPD esters in group F samples at 4°C

[0081]

[0082] Table 13 Short-term stability results of 3-MCPD esters in group F samples at 20°C

[0083]

[0084] Table 14 Short-term stability results of 3-MCPD esters in group F samples at 40°C

[0085]

[0086] Table 15 Long-term stability results of 3-MCPD esters in samples of group F stored at 2-8°C

[0087]

[0088] It can be seen from Tables 8 to 11 that the sunflower oil matrix standard samples containing 3-MCPD ester prepared by the method of the present invention in group A samples have good short-term stability and twelve-month long-term stability. β 1 |are both less than t 0.95，n-2 ×s( β 1 ), the content of 3-MCPD ester in the matrix standard sample tends to be stable, and the storage environment of 2-8°C can be determined as the storage environment of the matrix standard sample, with a total validity period of 24 months.

[0089] It can be seen from Tables 12 to 15 that the sunflower oil matrix standard sample containing chloropropanol prepared by the method of the present invention in group F samples has a short-term stability | β 1 |are both less than t 0.95，n-2 ×s( β 1 ), but in the twelve-month long-term stability study | β 1 |=0.011308564 is greater than t 0.95，n-2 ×s( β 1 ), the content of 3-MCPD ester in the matrix standard sample changes significantly, and the target substance changes significantly, then it can be considered that the long-term stability of the sample does not meet the expected requirements.

[0090] Example 6 Fixed value

[0091] The samples in Group A were valued in accordance with the requirements of "JJF 1343-2022 General Principles and Statistical Principles for the Value of Standard Materials". The value of the matrix standard sample was determined by the method of collaborative value determination of 9 laboratories, and all the laboratories participating in the value determination were qualified laboratories. The test results need to test whether the data obeys the normal distribution, and then use the Grubbs test to see if there are suspicious values ​​in the data in each laboratory, and use the Cochran test to determine whether the data between laboratories have the same accuracy. Only when the above requirements are met, the data is representative and can participate in the statistical analysis of the value determination results.

[0092] Table 16 Inter-laboratory determination data of matrix standard samples prepared by Group A

[0093]

[0094] The normality test uses the Shapiro-Wilk test method, and the table shows that W(n, p)=0.788 (where n=6, p=0.95). Since the W values ​​in the data of each laboratory are greater than 0.829, it can be considered that the test data of each laboratory are normally distributed.

[0095] The Grubbs test method is used to test whether the test results in each laboratory group have suspicious values. From the Grubbs critical value table, we know that λ （0.05,9） =2.215. The results show that the absolute value of the maximum residual value of the test results is less than λ （0.05,9） *S indicates that there are no abnormal values ​​or suspicious values ​​among the fixed-value results of each laboratory, so all data are retained and can be included in the fixed-value result statistics.

[0096] The Cochran test is used to determine whether the results of the values ​​determined by different laboratories are of equal precision. The Cochran test requires that C is less than or equal to C (α,m,n), indicating that the average values ​​of each group of data are of equal precision, otherwise it is judged as an outlier and the data group should be removed when calculating the fixed value result. (0.05,9,5) =0.3285. Table 16 shows that the C value of the Cochrane test is 0.1887, which is less than the critical value. The data between the laboratory test results are of equal precision, and all data should be retained and can be included in the statistics of the fixed value results.

[0097] According to the requirements of "JJF 1343-2022 General Principles and Statistical Principles for the Value of Standard Materials", after the suspicious value test and equal precision test of the value results of each laboratory, it is also necessary to test whether there is a significant difference in the average value of the value results of each laboratory and whether it meets the normality of the data distribution. After calculation, there is no significant difference between the average values ​​of the 9 laboratories and it meets the normality test. The data meets the statistical requirements. The standard value of the matrix standard sample prepared by Group A takes the average of the average results of each laboratory, that is, the standard value of the matrix standard sample prepared by Group A is 0.814 mg / kg.

[0098] Example 7 Uncertainty

[0099] According to "JJF 1343-2022 General Principles and Statistical Principles for the Determination of Standard Materials", the uncertainty of the determination results of standard materials consists of three parts: the uncertainty caused by the inhomogeneity of the standard material, the uncertainty caused by the instability of the standard material, and the uncertainty caused by the determination process of the standard material. By calculating the uncertainty of each part, the combined uncertainty U （y） , the confidence level is 95%, and the expanded uncertainty U is twice the combined uncertainty:

[0100] U （y） =√[(U bb ) 2 +(U sts ) 2 +(U char ) 2 ]

[0101] U = 2 × U （y）

[0102] U sts The uncertainty is caused by instability.

[0103] Uncertainty introduced by uniformity:

[0104] According to "JJF 1343-2022 General Principles and Statistical Principles for the Determination of Reference Materials", the intra-batch variance of group A samples is less than the inter-batch variance of samples ( ), and because u bb >s 2Therefore, the standard deviation of batch uniformity s can be estimated bb Equivalent to the uncertainty component u caused by batch-to-batch heterogeneity bb . Therefore u bb =0.0031 mg / kg.

[0105] Uncertainty introduced by stability:

[0106] According to the requirements of "JJF 1343-2022 General Principles and Statistical Principles for the Determination of Reference Materials", the stability change trend of Group A samples in Example 1 is not obvious. When using the trend analysis method for stability testing, the formula can be used: s =s(β1)·X to calculate the uncertainty introduced by stability. X is the sum of the long-term stability study time and the expected validity period, which is set to 24 months. It is known that s(β1)=0.000518 and X=24 months for the stability monitoring of the standard substance, so u s =0.01242mg / kg.

[0107] Uncertainty introduced by the fixed value:

[0108] The method used to determine the value of group A samples is to use a variety of methods with confirmed accuracy, and multiple laboratories cooperate to determine the value. Each laboratory only provides a series of observations. According to the requirements of the standard, in principle, the standard deviation of the mean value in this determination mode is the determination uncertainty u char .

[0109]

[0110] 9, indicating nine sets of data (measured by nine laboratories respectively); is the standard deviation of the mean of the nine groups of data; after calculation, the standard uncertainty u introduced by the laboratory joint determination is finally obtained char =0.1854mg / kg.

[0111] Therefore, the total combined uncertainty can be calculated as U （y） The final determined characteristic value of 3-MCPD ester in sunflower oil matrix standard sample of group A is 0.814±0.066mg / kg (k=2).

[0112] The above embodiments are only used to illustrate the technical solutions of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation shall fall within the protection scope of the present invention.

Claims

1. A sunflower oil matrix standard sample containing 3-chloropropanol ester, characterized in that: The preparation process is: Step 1: Take sunflower oil, add 0.2%-2.0% sodium chloride, 5-15% water and 1.0-6.0 mg / kg zinc chloride according to the weight of the oil, stir and treat at 160-200° C. for 2-4 hours to obtain a first oil sample; Step 2, cooling the first oil sample, performing refrigerated centrifugation, discarding the water layer, and obtaining a second oil sample; Step 3: Take the second oil sample, add 5-15% anion exchange resin and 0.5-1.5% cation exchange resin according to the weight of the oil, stir at 50-70°C for 2-4h, and filter to obtain the third oil sample; Step 4: Add 0.2-4.0 mg / kg of antioxidant to the third oil sample according to the weight of the oil, stir at 50-70° C. for 1-3 h, and mix thoroughly to obtain a fourth oil sample; Step 5: Centrifuge the fourth oil sample to obtain a sunflower oil matrix standard sample containing 3-chloropropanol ester.

2. A sunflower oil matrix standard sample containing 3-chloropropanol ester according to claim 1, characterized in that: In step three, the cation includes a zinc ion.

3. The sunflower oil matrix standard sample containing 3-chloropropanol ester according to claim 1, characterized in that: In step 1, 1.0% sodium chloride and 3.0 mg / kg zinc chloride were added according to the weight of the oil.

4. The sunflower oil matrix standard sample containing 3-chloropropanol ester according to claim 1, characterized in that: The sunflower seed oil matrix standard sample containing 3-chloropropanol ester obtained in step 5 is stored in a refrigerated state away from light.

5. The sunflower oil matrix standard sample containing 3-chloropropanol ester according to claim 1, characterized in that: In step three, 10% of strongly basic anion exchange resin and 1% of strongly acidic cation exchange resin were added according to the weight of the oil, and the mixture was stirred at 60° C. for 3 h. After completion, the third oil sample was obtained by filtration.

6. The sunflower oil matrix standard sample containing 3-chloropropanol ester according to claim 1, characterized in that: In step 4, 2.0 mg / kg of TBHQ antioxidant was added to the third oil sample according to the weight of the oil and mixed thoroughly.

7. A method for preparing a sunflower oil matrix standard sample containing 3-chloropropanol ester, characterized in that: The steps include: Step 1: Take sunflower oil, add 0.2%-2.0% sodium chloride, 5-15% water and 1.0-6.0 mg / kg zinc chloride according to the weight of the oil, stir and treat at 160-200° C. for 2-4 hours to obtain a first oil sample; Step 2, cooling the first oil sample, performing refrigerated centrifugation, discarding the water layer, and obtaining a second oil sample; Step 3: Take the second oil sample, add 5-15% anion exchange resin and 0.5-1.5% cation exchange resin according to the weight of the oil, stir at 50-70°C for 2-4h, and filter to obtain the third oil sample; Step 4: Add 0.2-4.0 mg / kg of antioxidant to the third oil sample according to the weight of the oil, stir at 50-70° C. for 1-3 h, and mix thoroughly to obtain a fourth oil sample; Step 5: Centrifuge the fourth oil sample to obtain a sunflower oil matrix standard sample containing 3-chloropropanol ester.

8. The method for preparing a sunflower oil matrix standard sample containing 3-chloropropanol ester according to claim 7, characterized in that: In step three, the cations include zinc ions; in step one, 1.0% sodium chloride and 3.0 mg / kg zinc chloride are added according to the weight of the oil.

9. The method for preparing a sunflower oil matrix standard sample containing 3-chloropropanol ester according to claim 7, characterized in that: In step three, 10% of strongly basic anion exchange resin and 1% of strongly acidic cation exchange resin were added according to the weight of the oil, and the mixture was stirred at 60° C. for 3 h. After completion, the third oil sample was obtained by filtration.

10. The method for preparing a sunflower oil-based standard sample containing 3-chloropropanol ester according to claim 7, characterized in that: In step 5, 2.0 mg / kg of TBHQ antioxidant was added to the fourth oil sample according to the weight of the oil and mixed thoroughly.

Images