Method for determining the migration of phthalate substances in food contact materials

Abstract

The present application relates to a method for determining the migration amount of phthalate esters in food contact materials, belonging to the technical field of food contact material processing, the method comprises the following steps: S1, taking a representative sample; S2, ultrasonic soluble or turbid sample; S3, aqueous, acidic, ethanol-containing food simulant (ethanol volume fraction <50%); S4, ethanol-containing food simulant (50% <= ethanol volume fraction <95%); S5, oil ester-containing food simulant, 5g (accurate to 0.01g) is taken; The present application has wide application range, high detection precision, strong data reliability, strong operation standardization and meets the safety supervision requirements.

Description

Technical Field

[0001] This invention belongs to the field of food contact material processing technology, specifically relating to a method for determining the migration amount of phthalate esters in food contact materials. Background Technology

[0002] Phthalate esters (PAEs) are a class of plasticizers widely used in the production of food contact materials. They are extensively added to resins, plastics, rubbers, coatings, and adhesives to effectively improve the flexibility, ductility, and processing properties of these materials. With the rapid development of the food industry, the variety of food contact materials has increased significantly, and their safety is directly related to consumer health. Phthalate esters are not tightly bound to the matrix molecules of food contact materials. During contact between the materials and food or food simulants, they easily migrate into the food and are subsequently ingested by the human body. Studies have shown that long-term intake of phthalate esters can adversely affect the human reproductive, endocrine, and immune systems, and may even pose a potential carcinogenic risk. Therefore, the detection of phthalate migration in food contact materials has become a key concern in the field of food safety. Currently, there are relevant standards both domestically and internationally for determining the migration of phthalate esters in food contact materials, but existing methods still have many shortcomings.

[0003] Insufficient Targeting of Sample Pretreatment: Different types of food contact materials (such as solid resins, thin-layer coatings, liquid coatings, etc.) have significant differences in physical morphology. Existing methods do not accurately differentiate pretreatment methods for samples of different morphologies, resulting in poor matching between sample particle size, extraction solvent, and sample, and low extraction efficiency of target substances. Complex Extraction and Purification Processes: Some methods use a single extraction solvent system and do not adopt differentiated post-treatment methods for samples with different solubility after ultrasonic extraction, which easily leads to problems such as turbidity of the extract and high levels of impurities. The purification steps for simulants containing oils are cumbersome and have poor purification effects, affecting the accuracy of subsequent instrument detection. Inconsistent Detection Methods for Different Food Simulants: Different types of food simulants, such as aqueous, acidic, ethanol-containing, and oil-containing simulants, have significantly different properties. Existing methods lack a systematic extraction, separation, and detection scheme, resulting in poor repeatability and comparability of detection results. Incomplete Uncertainty Assessment System: Some detection methods do not comprehensively analyze the sources of uncertainty in the detection process, nor do they establish scientific mathematical models for quantitative assessment, making it difficult to guarantee the accuracy and reliability of detection results. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining the migration amount of phthalate esters in food contact materials that is simple in structure and reasonably designed, in order to solve the above-mentioned problems.

[0005] The present invention achieves the above objectives through the following technical solutions: A method for determining the migration of phthalates in food contact materials includes the following steps: S1. Take representative samples. For solid samples such as resins, plastics, and rubber, cut them into small pieces, or cut them into small pieces and then freeze-crush them with liquid nitrogen, controlling the fragment size to ≤0.1cm. Mix well. For thin solid samples such as coatings and adhesives, scrape them with a knife, or scrape them with a knife and then cut them into small pieces or freeze-crush them with liquid nitrogen, controlling the fragment size to ≤0.3cm. Mix well. For liquid samples such as paints and adhesives, take samples directly. Accurately weigh 0.2g~0.5g of the sample (accurate to 0.0001g) into a centrifuge tube, add 10mL of tetrahydrofuran, and extract by ultrasonication for 30min. S2. For samples that are soluble or turbid during ultrasonication, extract and slowly add 40 mL of n-hexane, vortex, centrifuge at 4000 r / min for 20 min, take the supernatant and evaporate under reduced pressure to about 3 mL at 45 °C, make up to 10 mL with n-hexane, filter through a 0.45 μm organic phase glass membrane, and analyze by gas chromatography-mass spectrometry; For samples that are insoluble or precipitate during ultrasonication, extract and filter, add 10 mL of tetrahydrofuran to the residue, extract ultrasonically for 30 min, filter, combine the two filtrates, evaporate under reduced pressure to about 3 mL at 45 °C, make up to 10 mL with n-hexane, filter through a 0.45 μm organic phase glass membrane, and analyze by gas chromatography-mass spectrometry. S3. Aqueous, acidic, ethanol-containing food simulant (ethanol volume fraction <50%): Accurately transfer 10 mL of the soaking solution into a 25 mL centrifuge tube, add 4 mL of n-hexane, vortex for 10 min, centrifuge at 4000 r / min for 5 min, collect the n-hexane layer, repeat the extraction twice, combine the extracts, evaporate the extract to dryness under reduced pressure at 45℃, add 1 mL of n-hexane, vortex to reconstitute, and collect the supernatant for instrument analysis; S4. For ethanol-containing food simulant (50% ≤ ethanol volume fraction < 95%), accurately transfer 10 mL of the soaking solution into a 50 mL centrifuge tube, add 10 mL of water and 8 mL of n-hexane, vortex for 10 min, centrifuge at 4000 r / min for 5 min, collect the n-hexane layer, repeat the extraction twice, combine the extracts, evaporate the extract to dryness under reduced pressure at 45℃, add 1 mL of n-hexane, vortex to reconstitute, and collect the supernatant for instrument analysis; For 95% (volume fraction) ethanol and isooctane as chemical substitutes, accurately transfer 10 mL of the soaking solution into a flask, evaporate to dryness under reduced pressure at 45℃, add 1 mL of n-hexane, vortex to reconstitute, and collect the supernatant for instrument analysis. S5. For the ester-containing food simulant, weigh 5g (accurate to 0.01g) of the soaking solution into a 50mL centrifuge tube, add 20mL of acetonitrile, vortex for 10min, centrifuge at 4000r / min for 10min, and collect the acetonitrile layer. Repeat the extraction once, combine the extracts in a flask, and rotary evaporate the combined acetonitrile extract under reduced pressure to about 3mL at 45℃ as the purification solution. Add 10mL of acetonitrile to the solid-phase extraction column for activation, and discard the eluent. Add the purification solution to the solid-phase extraction column, collect the eluent in n-hexane, vortex to redissolve, and use the supernatant for instrument analysis.

[0006] As a further optimization of the present invention, in steps S1 and S2, the control of the size of the sample after crushing affects the extraction of phthalic acid esters. For insoluble samples, the fragment size should be controlled to be ≤0.1cm by means of shearing, scraping or liquid nitrogen cryogenic crushing; for soluble samples, as well as insoluble thin film samples (such as plastic wrap, scraped coating, etc.), the fragment size can be controlled to be ≤0.3cm.

[0007] As a further optimization of the present invention, in steps S1 and S2, the mathematical model is established as follows: Quantitative detection formula: In the formula: — The content of a single phthalate compound in the sample, expressed in milligrams per kilogram (mg / kg); ———The mass concentration of a single phthalate compound in the sample extract, expressed in milligrams per liter (mg / L); ——— The mass concentration of a single phthalate compound in the blank extract, expressed in milligrams per liter (mg / L); ———Sample volume, in milliliters (mL); ———The dilution factor by which the test solution is diluted to ensure that the measured value is within the linear range of the standard curve; —Sample mass, in grams (g); Mathematical model: U 2 rel (X)= U 2 rel (C)+ U 2 rel (V)+U 2 rel (m) Among them U 2 rel (C)= U2 rel (C1) C1 represents the uncertainty arising from repeated measurements. Sample homogeneity, extraction factor, etc., are already reflected in repeated extraction measurements and can be disregarded. U 2 rel (X): The square of the relative combined standard uncertainty of the final measurement result X; U 2 rel (C), U 2 rel (V), U 2 rel (m): These are the squares of the relative standard uncertainties of the input concentration C, volume V, and mass m, respectively.

[0008] As a further optimization of the present invention, the sources of uncertainty are as follows: Figure 1 As shown W: Final measurement result (e.g., content, concentration, etc. of the substance to be measured); ρs: the mass concentration of the standard solution, whose uncertainty comes from the calibration process of the "standard solution concentration"; m: The mass being weighed, whose uncertainty comes from two aspects: "weighing error" and "calibration"; V: Volume measurement value (e.g., titration volume), its uncertainty comes from two aspects: "repeatability reading" and "calibration"; Arrow direction: indicates the propagation path of uncertainty, that is, how the uncertainty of each input quantity is propagated to the final result W through calculation relationships.

[0009] As a further optimization of the present invention, the uncertainty introduced by preparing the standard stock solution: when preparing the standard intermediate solution using a 2mL volumetric flask, the uncertainty includes three parts: First, regarding the uncertainty of volumetric flask volume, according to GB12806—2011 "Laboratory Glassware - Single-mark Volumetric Flasks": the permissible volume difference for a Class A single-mark 2mL volumetric flask is ±0.015mL, which, converted to a standard deviation based on uniform distribution, is... ; Second, the variation in filling the volumetric flask with liquid to the mark can be statistically analyzed by repeated weighing. After repeating 10 times, the standard deviation was found to be 0.011 mL. Third, because the coefficient of thermal expansion of glass is very small, the volume change caused by temperature can be ignored:

[0010] Standard solution volume The combined standard uncertainty.

[0011] As a further optimization of the present invention, in steps S3, S4 and S5, the mathematical model is established as follows: Quantitative detection formula: In the formula: — The content of a single phthalate compound in a food simulant, expressed in milligrams per liter (mg / L); ———The mass concentration of a single phthalate compound in the sample soaking solution, expressed in milligrams per liter (mg / L); ———The mass concentration of a single phthalate compound in the blank soaking solution, expressed in milligrams per liter (mg / L); ———Volume at constant volume, in milliliters (mL); ———The dilution factor by which the test solution is diluted to ensure that the measured value is within the linear range of the standard curve; — Sample volume, in milliliters (mL); Mathematical model: U 2 rel (X)= U 2 rel (C)+ U 2 rel (V)+U 2 rel (m) Among them U 2 rel (C)= U 2 rel (C1) C1 represents the uncertainty arising from repeated measurements. Sample homogeneity, extraction factor, etc., are already reflected in repeated extraction measurements and can be disregarded. U 2 rel (X): The square of the relative combined standard uncertainty of the final measurement result X; U 2 rel (C), U 2 rel (V), U 2 rel (m): These are the squares of the relative standard uncertainties of the input concentration C, volume V, and mass m, respectively.

[0012] As a further optimization of the present invention, the sources of uncertainty are as follows: Figure 1 As shown W: Final measurement result (e.g., content, concentration, etc. of the substance to be measured); ρs: the mass concentration of the standard solution, whose uncertainty comes from the calibration process of the "standard solution concentration"; m: The mass being weighed, whose uncertainty comes from two aspects: "weighing error" and "calibration"; V: Volume measurement value (e.g., titration volume), its uncertainty comes from two aspects: "repeatability reading" and "calibration"; Arrow direction: indicates the propagation path of uncertainty, that is, how the uncertainty of each input quantity is propagated to the final result W through calculation relationships.

[0013] As a further optimization of the present invention, the uncertainty introduced by the preparation of the standard stock solution; The uncertainty of preparing a standard intermediate solution using a 2 mL volumetric flask comprises three parts: First, regarding the uncertainty of volumetric flask volume, according to GB12806—2011 "Laboratory Glassware - Single-mark Volumetric Flasks": the permissible volume difference for a Class A single-mark 2mL volumetric flask is ±0.015mL, which, converted to a standard deviation based on uniform distribution, is... ; Second, the variation in filling the volumetric flask with liquid to the mark can be statistically analyzed by repeated weighing. After repeating 10 times, the standard deviation was found to be 0.011 mL. Third, because the coefficient of thermal expansion of glass is very small, the volume change caused by temperature can be ignored:

[0014] Standard solution volume The combined standard uncertainty.

[0015] As a further optimization of the present invention, the uncertainty is taken as an example of the limit of detection of phthalates: The sample recovery rate was determined 6 times, and its uncertainty U(C2) = S(x) is given by the relative standard uncertainty:

[0016] Composition, expansion and representation of uncertainty Therefore, the uncertainty in the synthesis of phthalate is:

[0017] Final measurement results The relative combined standard uncertainty; Urel (C1), U rel (V), U rel (C2) represents the relative standard uncertainty of the input concentration C1, volume V, and concentration C2, respectively. The square root of the sum of squares: This is the core rule of uncertainty composition; when multiple independent inputs are multiplied / divided to obtain the final result, the total relative uncertainty is the square root of the sum of the squares of the components, rather than a simple sum. Taking the coverage factor k=2, the expanded uncertainty is: U(X) = k × U rel (X) × =mg / L, therefore, the result can be expressed as X=mg / L (k=2)U rel (C2) U(X): The expanded uncertainty (absolute uncertainty) of the final result X; k: Coverage factor. In the question, k=2 is the most commonly used value, corresponding to a confidence probability of about 95%. U rel (X): The relative combined standard uncertainty of result X; X: The numerical value of the measurement result (in mg / L); This formula converts relative uncertainty (dimensionless) into absolute uncertainty with the same unit as the result.

[0018] As a further optimization of the present invention, the uncertainty is taken as an example of the uncertainty of the repeatability experiment of detecting 4% acetic acid simulated solution in a sample: The sample recovery rate was determined 6 times, and its uncertainty U(C2) = S(x) is given by the relative standard uncertainty:

[0019] Composition, expansion, and representation of uncertainties in the synthesis of phthalate esters: Final measurement results The relative combined standard uncertainty; U rel (C1), U rel (V), U rel (C2), U rel (C3) represents the relative standard uncertainty of the input quantities (such as the concentrations C1, C2, and C3 of different solutions, and the volume V); The square root of the sum of squares: This is the core rule of uncertainty composition. When multiple independent inputs are multiplied / divided to obtain the final result, the total relative uncertainty is the square root of the sum of the squares of the components, not a simple summation. Taking the coverage factor k=2, the expanded uncertainty is: U(X) = k × U rel (X) × =mg / L Therefore, the result is expressed as X=mg / L (k=2)U(X): the expanded uncertainty (absolute uncertainty) of the final result X.

[0020] The beneficial effects of this invention are as follows: 1. This invention has a wide range of applications: the method can cover solid samples such as resin, plastic, and rubber, thin solid samples such as coatings and adhesive layers, and liquid samples such as paints and adhesives; it is also suitable for water-based, acidic, and food simulants with different ethanol volume fractions (<50%, 50%~95%, 95%) and oil-containing food simulants, and can meet the detection needs of various types of food contact materials and food simulation systems.

[0021] 2. This invention offers high detection accuracy: By controlling the pulverization size according to the different characteristics of various samples (≤0.1cm for insoluble samples, ≤0.3cm for soluble / thin-layer samples), and combining pretreatment methods such as ultrasonic extraction, vortex oscillation, vacuum rotary evaporation, and solid-phase extraction, the extraction efficiency and purification effect of phthalic acid esters are effectively improved, and matrix interference is reduced. Spiked recovery experiments verify that the recovery rate of the target substance in different food simulants is stable between 85.56% and 113.50%, with a relative standard deviation (RSD) of less than 20%, meeting the precision requirements of the detection method. The detection limit and quantitation limit reach low concentration levels (detection limit of most substances is 0.01mg / L or 0.01mg / kg), enabling accurate quantification of trace phthalic acid esters.

[0022] 3. The data reliability of this invention is strong: It establishes a complete quantitative detection mathematical model and uncertainty assessment system, clarifies the sources of uncertainty such as calibration and weighing errors, and completes the synthesis, expansion and representation of uncertainty through repeatability experiments, ensuring the accuracy and traceability of the detection results and providing a scientific basis for data interpretation.

[0023] 4. Strong operational standardization: The pretreatment steps and instrument detection process are standardized, the reagents and consumables used are non-interfering, and the experimental parameters (such as centrifugation speed, ultrasonic time, evaporation temperature, etc.) are clearly defined, which facilitates repeated operation by laboratory personnel. The detection can be completed on conventional gas chromatography-mass spectrometry (GC-MS) equipment, and the threshold for promotion and application is low.

[0024] 5. This invention meets the requirements of safety supervision: Phthalate esters are key controlled hazardous substances in food contact materials. This method can accurately measure their migration amount, providing reliable technical support for the safety evaluation and quality supervision of food contact materials, and helping to ensure food safety. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the sources of uncertainty in this invention. Detailed Implementation

[0026] The present application will now be described in further detail. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0027] Example 1: A method for determining the migration of phthalates in food contact materials, comprising four core steps: S1. Take representative samples. For solid samples such as resins, plastics, and rubber, cut them into small pieces, or cut them into small pieces and then freeze-crush them with liquid nitrogen, controlling the fragment size to ≤0.1cm, and mix well. For thin-layer solid samples such as coatings and adhesives, scrape them with a knife, or scrape them with a knife and then cut them into small pieces or freeze-crush them with liquid nitrogen, controlling the fragment size to ≤0.3cm, and mix well. For liquid samples such as paints and adhesives, take samples directly, accurately weigh 0.2g~0.5g of the sample (accurate to 0.0001g) into a centrifuge tube, add 10mL of tetrahydrofuran, and extract by ultrasonication for 30min. S2. For samples that are soluble or turbid during ultrasonication, extract and slowly add 40 mL of n-hexane, vortex, centrifuge at 4000 r / min for 20 min, take the supernatant and evaporate under reduced pressure to about 3 mL at 45 °C, make up to 10 mL with n-hexane, filter through a 0.45 μm organic phase glass membrane, and analyze by gas chromatography-mass spectrometry; For samples that are insoluble or precipitate during ultrasonication, extract and filter, add 10 mL of tetrahydrofuran to the residue, extract ultrasonically for 30 min, filter, combine the two filtrates, evaporate under reduced pressure to about 3 mL at 45 °C, make up to 10 mL with n-hexane, filter through a 0.45 μm organic phase glass membrane, and analyze by gas chromatography-mass spectrometry. The size control of the sample after crushing affects the extraction of phthalic acid esters. For insoluble samples, the fragment size should be controlled to ≤0.1cm by methods such as shearing, scraping or liquid nitrogen cryogenic crushing. For soluble samples, as well as insoluble thin film samples (such as plastic wrap, scraped coatings, etc.), the fragment size can be controlled to ≤0.3cm.

[0028] Preparation of standard solutions and reagents: Prepared in accordance with GB 31604.30-2025.

[0029] Note: Because the concentrations of the 19 mixed standard solutions prepared are different, for ease of expression, the concentrations of the mixed standards in this article will be calculated based on the DMP concentration. Table 1 shows the concentrations of the mixed standard curves for 19 phthalate esters in n-hexane (Part 1). DMP 1755 2511 4787 12465 21907 47295 0.997 DEP 1976 2431 4866 14850 25713 56069 0.997 DAP 652 834 1913 5404 10022 21714 0.998 DIBP 3926 4527 8062 22723 41803 88072 0.998 DBP 4684 5073 9135 25505 47003 97410 0.999 BMPP 2263 2398 5317 12764 25607 53585 0.999 DMEP 1920 2335 4927 13185 28369 58229 0.999 DPP 3381 4357 7923 22295 42701 88679 0.999 DEEP 497 620 1200 3143 5876 12033 0.999 DHXP 3731 4132 8884 22977 48355 95107 0.999 BBP 1454 1587 3365 8402 17834 35953 0.999 DCHP 3034 3512 6648 16431 37606 71342 0.998 DBEP 569 724 919 2830 6875 13902 0.997 DPH 1144 1510 2779 8030 17224 33709 0.999 DEHP 2897 3250 572 14237 30938 57863 0.998 DNOP 7360 8689 17653 47237 105354 195498 0.997 DNP 522 546 1215 3434 7093 13771 0.995 DINP-1 6779 9832 2238 61301 111826 230751 0.999 DIDP-1 966 7451 14115 51084 111283 217458 0.998 DINP-2 4763 6222 9956 24320 55123 113813 0.998 DINP-2 1211 2590 7529 2595 59648 120636 0.999 Measurement: Sample measurement Table 2. Test results of plastic cup samples

[0030] Blank assay; Except for the absence of a sample, the determination method in GB 31604.30-2025 was used, and the experimental result was not detected.

[0031] Note: When determining the concentrations of diisononyl phthalate and di-C8~C10 branched alkyl phthalates (C9 enrichment), diisodecyl phthalate and di-C9~C11 branched alkyl phthalates (C10 enrichment) in the test solution of plastic samples, DINP-1 and DIDP-1 are selected as standards, respectively; when determining the concentrations of other samples such as rubber, adhesives, coatings and coatings, paper and paperboard, DINP-2 and DIDP-2 are selected as standards.

[0032] Accuracy (recovery rate) and precision; The recovery rate and precision of the method were verified using the blank samples described above. Two-level experiments were conducted at two concentrations, with the limit of detection and the limit of quantitation selected.

[0033] Spicing experiments were conducted on food simulant samples; The sample was spiked at the limit of detection (LOD) for one time. Table 3 Results of the spiked test for the one-time detection limit of plastic cup samples

[0034] Perform a spike test at the limit of quantitation (LOQ) on the sample; Table 4 Results of the spiked test at one limit of quantitation for plastic cup samples

[0035] Perform a double limit of quantitation spike test on the sample; Table 5 Results of the double limit of quantitation spiked test on plastic cup samples (aqueous soaking solution).

[0036] Perform a 10-fold limit of quantitation spike test on the sample; Table 6 Results of the tenfold limit of quantitation spiked test on plastic cup samples

[0037] If the relative standard deviation (RSD%) of each group of data in Tables 3, 4, 5, and 6 is less than 20%, then the method has good stability for the phthalate content test and can meet the precision requirements of the standard.

[0038] Spiked recycling: The spike recovery rate of this method can be obtained from the data obtained from the operations in Tables 3, 4, 5, and 6. The specific results are shown in Tables 7, 8, 9, and 10 below.

[0039] Table 7 Results of the spiked test for the one-time detection limit of plastic cup samples

[0040] Table 8 Results of the spiked test at one limit of quantitation for plastic cup samples

[0041] Table 9 Results of the double limit of quantitation spiked test on plastic cup samples

[0042] Table 10 Results of the tenfold limit of quantitation spiked test on plastic cup samples

[0043] The 19 phthalate standard solutions used in this experiment were at a concentration of 10 mg / L. The spiking amounts on food contact materials were 40 µL, 50 µL, 100 µL, and 1000 µL, respectively. The recoveries ranged from 81.12% to 108.75%, and the precision ranged from 1.40% to 13.75%, which met the requirements for recovery and precision for the validation of this method.

[0044] Limit of detection and limit of quantitation; When the sample size is 0.4g and the volume is 10mL, the detection limits for DINP and DIDP in food contact materials according to GB 31604.30-2025 method are 1mg / L and quantitation limits are 2.5mg / L, the detection limits for DNP and DNOP are 2.5mg / L and quantitation limits are 5.0mg / L, and the detection limits for the remaining phthalates are 25mg / L and quantitation limits are 50mg / L. The S / N ratio is >3, which meets the requirements.

[0045] Reagent and consumable evaluation; The reagents and consumables used in this method do not interfere with the test results and can be used.

[0046] Establishment of mathematical models Quantitative detection formula: In the formula: X — The content of a single phthalate compound in the sample, expressed in milligrams per kilogram (mg / kg); C — Mass concentration of a single phthalate compound in the sample extract, expressed in milligrams per liter (mg / L); C0 — Mass concentration of a single phthalate compound in the blank extract, expressed in milligrams per liter (mg / L); V ———The final volume of the sample, in milliliters (mL); N ——— The dilution factor by which the test solution is diluted to ensure that the measured value is within the linear range of the standard curve; m — Sample mass, in grams (g); Mathematical model: U 2 rel (X)= U 2 rel (C)+ U 2 rel (V)+U 2 rel (m) Among them U 2 rel (C)= U 2 rel (C1) C1 represents the uncertainty arising from repeated measurements. Sample homogeneity and extraction factor are already reflected in repeated extraction measurements and can be disregarded.

[0047] Sources of uncertainty, such as Figure 1 As shown Uncertainty component evaluation; Uncertainty U of the concentration of the prepared standard solution rel (C1); The uncertainty of a standard substance, U[P(standard)]; The uncertainty U[P(standard)] is calculated according to the supplier catalog and the uniform distribution, as shown in Table 1.

[0048] Table 1 Uncertainty of Standard Reference Materials Other phthalates 2% 0.03 DINP 2% 0.01 DIDP 2% 0.01 Uncertainty introduced by the preparation of standard stock solutions: The uncertainty of preparing a standard intermediate solution using a 2 mL volumetric flask comprises three parts: First, regarding the uncertainty of volumetric flask volume, according to GB12806—2011 "Laboratory Glassware - Single-mark Volumetric Flasks": the permissible volume difference for a Class A single-mark 2mL volumetric flask is ±0.015mL, which, converted to a standard deviation based on uniform distribution, is... Second, the variation in filling the volumetric flask with liquid to the mark can be statistically analyzed by repeated weighing. After repeating 10 times, the standard deviation was found to be 0.011 mL. Third, because the coefficient of thermal expansion of glass is very small, the volume change caused by temperature is negligible.

[0049]

[0050]

[0051] The standard uncertainty U introduced using a 1 ml pipette rel,2 (V2) consists of two parts: First, regarding the uncertainty of a 1 ml pipette, according to the JJG 646-2006 Pipette Verification Procedure, the permissible error for a 1 ml pipette is ±1.0%, or 0.01 mL. Converted to standard deviation based on a uniform distribution, this is:

[0052] Second, the variability in the volume of solution transferred can be statistically analyzed by repeated weighing. After repeating the weighing six times and ignoring minor weighing errors, we obtain: U ＇ r,2 =

[0053]

[0054] The standard uncertainty U introduced using a 0.1 ml pipette rel,5 (V5) consists of two parts: Third, regarding the uncertainty of a 0.1 mL pipette, according to JJG 646-2006 Pipette Verification Procedure, the permissible error for a 0.1 mL pipette is ±2.0%, or 0.002 mL. Converting this to a standard deviation based on a uniform distribution yields...

[0055] Fourth, the variability in the volume of solution transferred can be statistically analyzed by repeated weighing. After repeating the weighing six times and ignoring minor weighing errors, we obtain:

[0056]

[0057]

[0058]

[0059] Table 2. Relative standard uncertainty of standard sample preparation

[0060] Uncertainty U introduced by sample weighing rel (m); The weighed mass is 0.4g, and the weighing uncertainty comes from two aspects: First, the standard deviation of the weighing variability is 0.08 mg within 50g. Second, the uncertainty arising from the balance calibration, according to the calibration certificate from the Shanghai Institute of Metrology and Testing Technology, is -0.2 for the indication error, which translates to a standard deviation of... .

[0061] The combined results of these two factors yield the following standard deviation for the weighing:

[0062]

[0063] The relative standard uncertainty of the sample weighing is very small and can be ignored.

[0064] The uncertainty introduced by the sample volume determination is U(V); The uncertainty of preparing a standard intermediate solution using a 10 mL volumetric flask comprises three parts: First, regarding the uncertainty of volumetric flask volume, according to GB12806—2011 "Laboratory Glassware - Single-mark Volumetric Flasks": the permissible volume difference for a Class A single-mark 2mL volumetric flask is ±0.015mL, which, converted to a standard deviation based on uniform distribution, is... Second, the variation in filling the volumetric flask with liquid to the mark can be statistically analyzed by repeated weighing. After repeating 10 times, the standard deviation was found to be 0.011 mL. Third, because the coefficient of thermal expansion of glass is very small, the volume change caused by temperature can be ignored:

[0065]

[0066] Uncertainty; Taking the limit of detection of phthalates as an example: The sample recovery rate was determined 6 times, and its uncertainty U(C2) = S(x) is given by the relative standard uncertainty:

[0067] Composition, expansion, and representation of uncertainty; Therefore, the uncertainty in the synthesis of phthalate is: Taking the coverage factor k=2, the expanded uncertainty is: U(X) = k × U rel (X) × =mg / L, therefore, the result can be expressed as X=mg / L (k=2)U rel (C2) is shown in Table 3 below: Table 3. Detection limits of 19 phthalates in plastic cups by GC-MS: 40 μg / mL (uncertain).

[0068] S3. Aqueous, acidic, ethanol-containing food simulant (ethanol volume fraction <50%): Accurately transfer 10 mL of the soaking solution into a 25 mL centrifuge tube, add 4 mL of n-hexane, vortex for 10 min, centrifuge at 4000 r / min for 5 min, collect the n-hexane layer, repeat the extraction twice, combine the extracts, evaporate the extract to dryness under reduced pressure at 45℃, add 1 mL of n-hexane, vortex to reconstitute, and collect the supernatant for instrument analysis; S4. For the ethanol-containing food simulant (50% ≤ ethanol volume fraction < 95%), accurately transfer 10 mL of the soaking solution into a 50 mL centrifuge tube, add 10 mL of water and 8 mL of n-hexane, vortex for 10 min, centrifuge at 4000 r / min for 5 min, collect the n-hexane layer, repeat the extraction twice, combine the extracts, evaporate the extract to dryness under reduced pressure at 45℃, add 1 mL of n-hexane, vortex to reconstitute, and collect the supernatant for instrument analysis; For the 95% (volume fraction) ethanol and isooctane chemical substitute solvent, accurately transfer 10 mL of the soaking solution into a flask, evaporate to dryness under reduced pressure at 45℃, add 1 mL of n-hexane, vortex to reconstitute, and collect the supernatant for instrument analysis.

[0069] S5. For the ester-containing food simulant, weigh 5g (accurate to 0.01g) of the soaking solution into a 50mL centrifuge tube, add 20mL of acetonitrile, vortex for 10min, centrifuge at 4000r / min for 10min, and collect the acetonitrile layer. Repeat the extraction once, combine the extracts in a flask, and rotary evaporate the combined acetonitrile extract under reduced pressure to about 3mL at 45℃ as the purification solution. Add 10mL of acetonitrile to the solid-phase extraction column for activation, and discard the eluent. Add the purification solution to the solid-phase extraction column, collect the eluent in n-hexane, vortex to redissolve, and use the supernatant for instrument analysis.

[0070] Preparation of standard solutions and reagents; Prepared in accordance with GB 31604.30-2025.

[0071] Note: Due to the different concentrations of the 19 mixed standard solutions prepared, for ease of expression, the concentrations of the mixed standards in this article will be calculated based on the DMP concentration. Standard curve The concentrations of 19 phthalate standard curves in aqueous, acidic, ethanolic, and oily simulants are shown in Tables 1, 2, 3, and 4. Table 1: Concentration of 4% Acetic Acid Analog Standard Solutions of 19 Phthalate Esters

[0072] Table 2: Concentration of 50% ethanol simulants of 19 phthalates in standard solutions

[0073] Table 3: Concentration of 95% ethanol simulants of 19 phthalates in standard solutions

[0074] Table 4: Concentration of Standard Solutions of 19 Phthalate Ester Vegetable Oil Analogs

[0075] Sample determination Table 5. Test results of plastic cup samples (4% acetic acid soaking solution)

[0076] Table 6. Test results of plastic cup samples (50% ethanol immersion solution)

[0077] Table 7. Test results of plastic cup samples (95% ethanol immersion solution)

[0078] Table 8. Test results of plastic cup samples (vegetable oil soaking solution)

[0079] Blank assay; Except for the absence of a sample, the determination method in GB 31604.30-2025 was used, and the experimental result was not detected.

[0080] Accuracy (recovery rate) and precision; The recovery rate and precision of the method were verified using the blank samples described above. Two-level experiments were conducted at two concentrations, with the limit of detection and the limit of quantitation selected.

[0081] Spiking test on 4% acetic acid food simulant sample Table 9 Results of spiked tests on plastic cup samples (4% acetic acid soaking solution) at 1, 5, and 10 times the detection limit.

[0082] Spiking experiment on 50% ethanol food simulant samples Table 10 Results of spiked tests on plastic cup samples (50% ethanol immersion solution) at 1, 5, and 10 times the detection limit.

[0083] Spiking experiments were conducted on 95% ethanol food simulant samples: Table 11 Results of Spiked Tests on Plastic Cup Samples (95% Ethanol Immersion Solution) at 1, 5, and 10 Times Detection Limits

[0084] Spiking experiments were conducted on olive oil food simulant samples. Table 12 Results of Spiked Tests on Plastic Cup Samples (Olive Oil Infusion) at 1, 5, and 10 Times Detection Limits

[0085] The relative standard deviation (RSD%) of each group of data in Tables 9, 10, 11, and 12 is less than 15%, indicating that the method has good stability for the migration test of phthalates and can meet the precision requirements of the standard.

[0086] Spiked recycling; The spike recovery rate of this method can be obtained from the data obtained from the operation in Tables 9, 10, 11 and 12. The specific results are shown in Tables 13, 14, 15 and 16 below.

[0087] Spiking experiments were conducted on food simulant samples containing 4% acetic acid. Table 13 Results of Spiking Tests on Plastic Cup Samples (4% Acetic Acid Immersion Solution) at 1, 5, and 10 Times Detection Limits

[0088] Spiking experiments were conducted on 50% ethanol food simulant samples: Table 14 Results of spiked tests on plastic cup samples (50% ethanol immersion solution) at 1, 5, and 10 times the detection limit.

[0089] Spiking experiments were conducted on 95% ethanol food simulant samples: Table 15 Results of Spiking Tests on Plastic Cup Samples (95% Ethanol Immersion Solution) at 1, 5, and 10 Times Detection Limits

[0090] Spiking experiments were conducted on olive oil food simulant samples: Table 16 Results of Spiked Tests on Plastic Cup Samples (Olive Oil Infusion) at 1, 5, and 10 Times Detection Limits

[0091] The 19 phthalate standard solutions used in this experiment were at a concentration of 1 mg / L. The spiking volumes of the simulants were 10 µL, 50 µL, and 100 µL, respectively. The recoveries of the 4% acetic acid food simulant were between 85.56% and 106.06%, with a precision of 0.63%–8.35%; the recoveries of the 50% ethanol food simulant were between 91.26% and 101.85%, with a precision of 1.19%–6.89%; the recoveries of the 95% ethanol food simulant were between 90.01% and 99.22%, with a precision of 1.73%–9.96%; and the recoveries of the vegetable oil food simulant were between 86.29% and 113.50%, with a precision of 1.63%–13.33%, all of which met the requirements.

[0092] Limit of detection and limit of quantitation When the area / volume ratio of the sample in the migration test is consistent with the area / volume ratio of the sample in contact with food during actual use, this method provides the following limits of detection (LOD) for DINP-1 / -2 and DIDP-1 / -2 in water-based, acidic, ethanol-containing, isooctane-containing, and 95% (volume fraction) ethanol simulated solutions: 0.5 mg / L and 1.0 mg / L; for DBP: 0.02 mg / L and 0.05 mg / L; for DEHP: 0.05 mg / L and 0.10 mg / L; and for other phthalate compounds: 0.01 mg / L and 0.10 mg / L. For vegetable oil simulated solutions: 0.5 mg / kg for DINP-1 / -2 and 1.0 mg / kg; and for DBP: 0.02 mg / kg and 0.05 mg / kg. The detection limit for DEHP was 0.05 mg / kg and the quantitation limit was 0.10 mg / kg; the detection limits for other phthalic acid esters were 0.01 mg / kg and the quantitation limits were 0.10 mg / kg, which met the requirements.

[0093] Reagent and Consumable Evaluation The reagents and consumables used in this method do not interfere with the test results and can be used.

[0094] The establishment of mathematical models; Quantitative detection formula: In the formula: X1 — The content of a single phthalate compound in the food simulant, expressed in milligrams per liter (mg / L); C — Mass concentration of a single phthalate compound in the sample immersion solution, in milligrams per liter (mg / L); C0 — Mass concentration of a single phthalate compound in the blank soaking solution, expressed in milligrams per liter (mg / L); V ——— Fixed volume, in milliliters (mL); N ——— The dilution factor by which the test solution is diluted to ensure that the measured value is within the linear range of the standard curve; V0 — Sample volume, in milliliters (mL).

[0095] Mathematical model: U 2 rel (X)= U 2 rel (C)+ U 2 rel (V)+U 2 rel (m) Among them U 2 rel (C)= U 2 rel (C1) C1 represents the uncertainty arising from repeated measurements. Sample homogeneity and extraction factor are already reflected in repeated extraction measurements and can be disregarded.

[0096] Sources of uncertainty, such as Figure 1 As shown Uncertainty component evaluation; Uncertainty U of the concentration of the prepared standard solution rel (C1); The uncertainty of a standard substance, U[P(standard)]; The uncertainty U[P(standard)] is calculated according to the supplier catalog and the uniform distribution, as shown in Table 1.

[0097] Table 1: Uncertainty of Standard Reference Materials Uncertainty introduced by the preparation of standard stock solutions; The uncertainty of preparing a standard intermediate solution using a 2 mL volumetric flask comprises three parts: First, regarding the uncertainty of volumetric flask volume, according to GB12806—2011 "Laboratory Glassware - Single-mark Volumetric Flasks": the permissible volume difference for a Class A single-mark 2mL volumetric flask is ±0.015mL, which, converted to a standard deviation based on uniform distribution, is... Second, the variation in filling the volumetric flask with liquid to the mark can be statistically analyzed by repeated weighing. After repeating 10 times, the standard deviation was found to be 0.011 mL. Third, because the coefficient of thermal expansion of glass is very small, the volume change caused by temperature is negligible.

[0098]

[0099]

[0100] The standard uncertainty U introduced using a 1 ml pipette rel,2 (V2) consists of two parts: First, regarding the uncertainty of a 1 ml pipette, according to the JJG 646-2006 Pipette Verification Procedure, the permissible error for a 1 ml pipette is ±1.0%, or 0.01 mL. Converted to standard deviation based on a uniform distribution, this is:

[0101] Second, the variability in the volume of solution transferred can be statistically analyzed by repeated weighing. After repeating the weighing six times and ignoring minor weighing errors, we obtain: U ＇ r,2 =

[0102]

[0103] The standard uncertainty U introduced using a 0.1 ml pipette rel,5 (V5) consists of two parts: First, regarding the uncertainty of a 0.1 mL pipette, according to JJG 646-2006 Pipette Verification Procedure, the permissible error for a 0.1 mL pipette is ±2.0%, or 0.002 mL. Converting this to a standard deviation based on a uniform distribution yields...

[0104] Second, the variability in the volume of solution transferred can be statistically analyzed by repeated weighing. After repeating the weighing six times and ignoring minor weighing errors, we obtain:

[0105]

[0106]

[0107] Table 2: Relative standard uncertainty of standard sample preparation

[0108] Uncertainty U(V) introduced by sample preparation; The uncertainty U is measured using a 200ml graduated cylinder. rel,1 (V1) consists of three parts: First, regarding the uncertainty of the graduated cylinder volume, according to GB12804—2011 "Laboratory Glassware Graduated Cylinders", the permissible difference in volume for a 200mL graduated cylinder is ±3.00mL. Converted to a standard deviation based on a uniform distribution, this is... Secondly, the variation in the liquid level when filled to the mark can be statistically analyzed by repeated weighing. After repeating the weighing 10 times, the standard deviation was found to be 0.16 mL. Third, because the coefficient of thermal expansion of glass is very small, the volume change caused by temperature is negligible.

[0109]

[0110]

[0111] The standard uncertainty U introduced using a 1 ml pipette rel,2 (V2) consists of two parts: (1) The uncertainty of a 1 mL pipette, according to the JJG 646-2006 pipette verification procedure, is: the permissible error of a 1 mL pipette is ±1.0%, i.e., 0.01 mL, which is converted to a standard deviation based on a uniform distribution.

[0112] (2) The variation in the volume of the solution transferred can be statistically analyzed by repeated weighing. After repeating the weighing 6 times and ignoring the small errors in weighing, we get: U ＇ r,2 =

[0113]

[0114] The standard uncertainty U introduced using a 5 ml pipette (twice) rel,3 (V3) consists of two parts: (1) The uncertainty of a 5 ml pipette, according to the JJG 646-2006 pipette verification procedure, is: the permissible error of a 5 mL pipette is ±0.6%, i.e., 0.006 mL. Converted to standard deviation based on uniform distribution, it is:

[0115] (2) The variation in the volume of solution transferred can be statistically analyzed by repeated weighing. After repeating the weighing 6 times and ignoring the small errors in weighing, we get:

[0116]

[0117]

[0118] Uncertainty; Take the uncertainty of repeatability test of sample detection of 4% acetic acid simulation solution as an example.

[0119] The sample recovery rate was determined 6 times, and its uncertainty U(C2) = S(x) is given by the relative standard uncertainty:

[0120] Composition, expansion, and representation of uncertainty: Uncertainty in the synthesis of phthalic acid esters:

[0121] Taking the coverage factor k=2, the expanded uncertainty is: U(X) = k × U rel (X) × =mg / L, therefore, the result can be expressed as X=mg / L (k=2). Table 3: GC-MS detection limit for 19 phthalates in transparent disposable plastic cups: 0.01 mg / L (uncertain). Table 4: Uncertainty of 0.05 mg / L concentration of 19 phthalates in transparent disposable plastic cups by GC-MS Table 5: Uncertainty of Detection Limit of 19 Phthalate Esters in GC-MS Transparent Disposable Plastic Cups (0.1 mg / L) The above embodiments are merely examples of several implementations of the present invention, and their descriptions are quite specific and detailed, but they should not be construed as limiting the scope of the present invention.

[0122] It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this invention, and these modifications and improvements are all within the scope of protection of this invention.

Claims

1. A method for determining the migration amount of phthalates in food contact materials, comprising the following steps: S1. Take representative samples. For solid samples such as resins, plastics, and rubber, cut them into small pieces, or cut them into small pieces and then freeze-crush them with liquid nitrogen, controlling the fragment size to ≤0.1cm. Mix well. For thin solid samples such as coatings and adhesives, scrape them with a knife, or scrape them with a knife and then cut them into small pieces or freeze-crush them with liquid nitrogen, controlling the fragment size to ≤0.3cm. Mix well. For liquid samples such as paints and adhesives, take samples directly. Accurately weigh 0.2g~0.5g of the sample (accurate to 0.0001g) into a centrifuge tube, add 10mL of tetrahydrofuran, and extract by ultrasonication for 30min. S2. For samples that are soluble or turbid during ultrasonication, extract and slowly add 40 mL of n-hexane, vortex, centrifuge at 4000 r / min for 20 min, take the supernatant and evaporate under reduced pressure to about 3 mL at 45 °C, make up to 10 mL with n-hexane, filter through a 0.45 μm organic phase glass membrane, and analyze by gas chromatography-mass spectrometry; For samples that are insoluble or precipitate during ultrasonication, extract and filter, add 10 mL of tetrahydrofuran to the residue, extract ultrasonically for 30 min, filter, combine the two filtrates, evaporate under reduced pressure to about 3 mL at 45 °C, make up to 10 mL with n-hexane, filter through a 0.45 μm organic phase glass membrane, and analyze by gas chromatography-mass spectrometry. S3. Aqueous, acidic, ethanol-containing food simulant (ethanol volume fraction <50%): Accurately transfer 10 mL of the soaking solution into a 25 mL centrifuge tube, add 4 mL of n-hexane, vortex for 10 min, centrifuge at 4000 r / min for 5 min, collect the n-hexane layer, repeat the extraction twice, combine the extracts, evaporate the extract to dryness under reduced pressure at 45℃, add 1 mL of n-hexane, vortex to reconstitute, and collect the supernatant for instrument analysis; S4. For ethanol-containing food simulant (50% ≤ ethanol volume fraction < 95%), accurately transfer 10 mL of the soaking solution into a 50 mL centrifuge tube, add 10 mL of water and 8 mL of n-hexane, vortex for 10 min, centrifuge at 4000 r / min for 5 min, collect the n-hexane layer, repeat the extraction twice, combine the extracts, evaporate the extract to dryness under reduced pressure at 45℃, add 1 mL of n-hexane, vortex to reconstitute, and collect the supernatant for instrument analysis; For 95% (volume fraction) ethanol and isooctane as chemical substitutes, accurately transfer 10 mL of the soaking solution into a flask, evaporate to dryness under reduced pressure at 45℃, add 1 mL of n-hexane, vortex to reconstitute, and collect the supernatant for instrument analysis. S5. For the ester-containing food simulant, weigh 5g (accurate to 0.01g) of the soaking solution into a 50mL centrifuge tube, add 20mL of acetonitrile, vortex for 10min, centrifuge at 4000r / min for 10min, and collect the acetonitrile layer. Repeat the extraction once, combine the extracts in a flask, and rotary evaporate the combined acetonitrile extract under reduced pressure to about 3mL at 45℃ as the purification solution. Add 10mL of acetonitrile to the solid-phase extraction column for activation, and discard the eluent. Add the purification solution to the solid-phase extraction column, collect the eluent in n-hexane, vortex to redissolve, and use the supernatant for instrument analysis.

2. The method for determining the migration amount of phthalate esters in food contact materials according to claim 1, characterized in that: In steps S1 and S2, the size control of the sample after crushing affects the extraction of phthalic acid esters. For insoluble samples, the fragment size should be controlled to ≤0.1cm by methods such as cutting, scraping or liquid nitrogen cryogenic crushing. For soluble samples, as well as insoluble thin film samples (such as plastic wrap, scraped coatings, etc.), the fragment size can be controlled to ≤0.3cm.

3. The method for determining the migration amount of phthalates in food contact materials according to claim 1, characterized in that: In steps S1 and S2, the mathematical model is established: Quantitative detection formula: In the formula: — The content of a single phthalate compound in the sample, expressed in milligrams per kilogram (mg / kg); ———The mass concentration of a single phthalate compound in the sample extract, expressed in milligrams per liter (mg / L); ——— The mass concentration of a single phthalate compound in the blank extract, expressed in milligrams per liter (mg / L); ———Sample volume, in milliliters (mL); ———The dilution factor by which the test solution is diluted to ensure that the measured value is within the linear range of the standard curve; —Sample mass, in grams (g); Mathematical model: U 2 rel (X) = U 2 rel (C)+ U 2 rel (V)+U 2 rel (m) Among them U 2 rel (C)= U 2 rel (C1) C1 represents the uncertainty arising from repeated measurements. Sample homogeneity, extraction factor, etc., are already reflected in repeated extraction measurements and can be disregarded. U 2 rel (X): The square of the relative combined standard uncertainty of the final measurement result X; U 2 rel (C), U 2 rel (V), U 2 rel (m): These are the squares of the relative standard uncertainties of the input concentration C, volume V, and mass m, respectively.

4. The method for determining the migration amount of phthalate esters in food contact materials according to claim 3, characterized in that: The source of uncertainty W: Final measurement result (e.g., content, concentration, etc. of the substance to be measured); ρs: the mass concentration of the standard solution, whose uncertainty comes from the calibration process of the "standard solution concentration"; m: The mass being weighed, whose uncertainty comes from two aspects: "weighing error" and "calibration"; V: Volume measurement value (e.g., titration volume), whose uncertainty comes from two aspects: "repeatability reading" and "calibration".

5. The method for determining the migration amount of phthalate esters in food contact materials according to claim 4, characterized in that: Uncertainty introduced by the preparation of standard stock solutions: The uncertainty of preparing standard intermediate solutions using 2 mL volumetric flasks includes three parts: First, regarding the uncertainty of volumetric flask volume, according to GB12806—2011 "Laboratory Glassware - Single-mark Volumetric Flasks": the permissible volume difference for a Class A single-mark 2mL volumetric flask is ±0.015mL, which, converted to a standard deviation based on uniform distribution, is... ; Second, the variation in filling the volumetric flask with liquid to the mark can be statistically analyzed by repeated weighing. After repeating 10 times, the standard deviation was found to be 0.011 mL. Third, because the coefficient of thermal expansion of glass is very small, the volume change caused by temperature can be ignored: Standard solution volume The combined standard uncertainty.

6. The method for determining the migration amount of phthalate esters in food contact materials according to claim 1, characterized in that: In steps S3, S4, and S5, the mathematical model is established: Quantitative detection formula: In the formula: — The content of a single phthalate compound in a food simulant, expressed in milligrams per liter (mg / L); ———The mass concentration of a single phthalate compound in the sample soaking solution, expressed in milligrams per liter (mg / L); ———The mass concentration of a single phthalate compound in the blank soaking solution, expressed in milligrams per liter (mg / L); ———Volume at constant volume, in milliliters (mL); ———The dilution factor by which the test solution is diluted to ensure that the measured value is within the linear range of the standard curve; — Sample volume, in milliliters (mL); Mathematical model: U 2 rel (X) = U 2 rel (C)+ U 2 rel (V)+U 2 rel (m) Among them U 2 rel (C)= U 2 rel (C1) C1 represents the uncertainty arising from repeated measurements. Sample homogeneity, extraction factor, etc., are already reflected in repeated extraction measurements and can be disregarded. U 2 rel (X): The square of the relative combined standard uncertainty of the final measurement result X; U 2 rel (C), U 2 rel (V), U 2 rel (m): These are the squares of the relative standard uncertainties of the input concentration C, volume V, and mass m, respectively.

7. The method for determining the migration amount of phthalate esters in food contact materials according to claim 6, characterized in that: The source of uncertainty W: Final measurement result (e.g., content, concentration, etc. of the substance to be measured); ρs: the mass concentration of the standard solution, whose uncertainty comes from the calibration process of the "standard solution concentration"; m: The mass being weighed, whose uncertainty comes from two aspects: "weighing error" and "calibration"; V: Volume measurement value (e.g., titration volume), whose uncertainty comes from two aspects: "repeatability reading" and "calibration".

8. The method for determining the migration amount of phthalate esters in food contact materials according to claim 7, characterized in that: Uncertainty introduced by the preparation of standard stock solutions; The uncertainty of preparing a standard intermediate solution using a 2 mL volumetric flask comprises three parts: First, regarding the uncertainty of volumetric flask volume, according to GB12806—2011 "Laboratory Glassware - Single-mark Volumetric Flasks": the permissible volume difference for a Class A single-mark 2mL volumetric flask is ±0.015mL, which, converted to a standard deviation based on uniform distribution, is... ; Second, the variation in filling the volumetric flask with liquid to the mark can be statistically analyzed by repeated weighing. After repeating 10 times, the standard deviation was found to be 0.011 mL. Third, because the coefficient of thermal expansion of glass is very small, the volume change caused by temperature can be ignored: Standard solution volume The combined standard uncertainty.

9. The method for determining the migration amount of phthalate esters in food contact materials according to claim 5, characterized in that: The uncertainty is exemplified by the limit of detection for phthalates: The sample recovery rate was determined 6 times, and its uncertainty U(C2) = S(x) is given by the relative standard uncertainty: Composition, expansion and representation of uncertainty Therefore, the uncertainty in the synthesis of phthalate is: Final measurement results The relative combined standard uncertainty; U rel (C1), U rel (V), U rel (C2) represents the relative standard uncertainty of the input concentration C1, volume V, and concentration C2, respectively. The square root of the sum of squares: This is the core rule of uncertainty composition; when multiple independent inputs are multiplied / divided to obtain the final result, the total relative uncertainty is the square root of the sum of the squares of the components, rather than a simple sum. Taking the coverage factor k=2, the expanded uncertainty is: U(X) = k × U rel (X) × =mg / L, therefore, the result can be expressed as X=mg / L (k=2)U rel (C2) U(X): The expanded uncertainty (absolute uncertainty) of the final result X; k: Coverage factor. In the question, k=2 is the most commonly used value, corresponding to a confidence probability of about 95%. U rel (X): The relative combined standard uncertainty of result X; X: The numerical value of the measurement result (in mg / L); This formula converts relative uncertainty (dimensionless) into absolute uncertainty with the same unit as the result.

10. The method for determining the migration amount of phthalate esters in food contact materials according to claim 8, characterized in that: The uncertainty is exemplified by the uncertainty of a repeatability test of a 4% acetic acid simulation solution for sample detection: The sample recovery rate was determined 6 times, and its uncertainty U(C2) = S(x) is given by the relative standard uncertainty: Composition, expansion and representation of uncertainty Uncertainty in the synthesis of phthalic acid esters: Final measurement results The relative combined standard uncertainty; U rel (C1), U rel (V), U rel (C2), U rel (C3) represent the relative standard uncertainty of the input quantities (such as the concentrations C1, C2, and C3 of different solutions, and the volume V); Square root of the sum of squares: This is the core rule of uncertainty composition. When multiple independent input quantities are multiplied / divided to obtain the final result, the total relative uncertainty is the square root of the sum of the squares of each component, not a simple summation. Taking the coverage factor k=2, the expanded uncertainty is: U(X) = k × U rel (X) × =mg / L Therefore, the result is expressed as X=mg / L (k=2)U(X): the expanded uncertainty (absolute uncertainty) of the final result X.

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