Method for detecting antioxidant in food contact plastic material or product thereof and application of method

Abstract

The invention provides a method for detecting an antioxidant in a food contact plastic material or a product thereof and application of the method. The detection method comprises the following steps: mixing a sample to be detected with an organic solvent, filtering, taking filtrate, carrying out gas chromatography-mass spectrometry detection, and calculating the content of the antioxidant in the sample to be detected according to a detection result, the antioxidant comprises any one or a combination of at least two of 2, 4-bis [(dodecylthio) methyl]-6-methylphenol, 2, 6-di-tert-butyl-4-ethylphenol or 2, 2 '-methylenebis [6-(1-methylcyclohexyl)-p-cresol]. The detection method provided by the invention is simple to operate, low in detection limit and quantitation limit, high in accuracy and excellent in repeatability and reproducibility, and can effectively and accurately detect the three phenolic antioxidants at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of food contact plastic material detection, and specifically relates to a method for detecting antioxidants in food contact plastic materials or products thereof and application thereof. Background Art

[0002] Phenolic antioxidants have excellent antioxidant properties. Their chemical properties are stable and can effectively protect polymer materials from oxidative damage. They are often used as additives in food contact materials to improve the heat and oxidation resistance of the materials, protect the materials from oxidation, and ensure the stability of food packaging.

[0003] 2,4-Bis[(dodecylthio)methyl]-6-methylphenol is a highly effective hindered phenolic antioxidant that can prevent or slow down oxidation reactions. It is often used as a plastic additive to improve the antioxidant properties of materials, thereby extending the service life of products and maintaining their performance. 2,6-Di-tert-butyl-4-ethylphenol is mainly used for antioxidant treatment of natural rubber, synthetic rubber and latex. It is also used in polymer materials such as plastics to improve their antioxidant properties. It has antioxidant and UV resistance and is often used to prepare preservatives, antioxidants and ultraviolet absorbers. In food contact materials, it is mainly used as an antioxidant for plastics, rubbers and oils to prevent oxidation and degradation of materials and maintain their performance and safety. 2,2'-Methylenebis[6-(1-methylcyclohexyl)-p-cresol] protects polymer materials from oxidation and extends the service life of materials by capturing free radicals and interrupting oxidation chain reactions.

[0004] Although the above three phenolic antioxidants have excellent chemical properties, with the study of their toxicology, more and more evidence shows that they pose many hazards to human health. If they come into contact with the eyes, these substances may cause serious damage or irritation to the eyes, with symptoms such as redness, swelling, pain, tearing or blurred vision. They may also cause corrosion or irritation to the skin, causing redness, itching, pain or burns. They may also irritate the respiratory system, causing respiratory discomfort or difficulty breathing.

[0005] Due to the complexity of the chemical structure of these three substances and the interference of similar compounds, the test results are easily inaccurate, especially the trace content is more difficult to detect. At present, there is no report on the detection method of 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,6-di-tert-butyl-4-ethylphenol and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] substances with a simple method, high accuracy, excellent repeatability and reproducibility. Therefore, how to provide a method that can effectively detect the above three antioxidants has become an urgent problem to be solved. Summary of the invention

[0006] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for detecting antioxidants in food contact plastic materials or their products and their application. The detection method provided by the present invention is simple to operate, has low detection limit and quantification limit, high accuracy, excellent repeatability and reproducibility, and can effectively and accurately detect three phenolic antioxidants simultaneously.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In one aspect, the present invention provides a method for detecting antioxidants in a food contact plastic material or its products, the detection method comprising the following steps:

[0009] The sample to be tested is mixed with an organic solvent, and then filtered, and the filtrate is subjected to gas chromatography-mass spectrometry detection, and the content of the antioxidant in the sample to be tested is calculated according to the detection result;

[0010] The antioxidant includes any one of 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,6-di-tert-butyl-4-ethylphenol or 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] or a combination of at least two thereof.

[0011] The above method treats the sample with a specific organic solvent and then performs gas chromatography-mass spectrometry detection. The overall method is simple to operate, has low detection limits and quantification limits, high accuracy, excellent repeatability and reproducibility, and can effectively and accurately detect multiple phenolic antioxidants at the same time.

[0012] Preferably, the food contact plastic material includes any one of polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), polyvinyl chloride (PVC), polystyrene (PS), nylon-6 (PA-6), polycarbonate (PC), polyoxymethylene (POM), polylactic acid (PLA) or polyethylene terephthalate (PET).

[0013] Preferably, the antioxidant is a combination of 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,6-di-tert-butyl-4-ethylphenol and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol].

[0014] Preferably, the organic solvent comprises a first solvent and a second solvent, the first solvent comprises n-hexane and / or cyclohexane, and the second solvent comprises any one of acetone, tetrahydrofuran or ethyl acetate or a combination of at least two thereof.

[0015] Since 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] are all compounds with weak polarity to non-polarity, non-polar solvents such as n-hexane and cyclohexane can be selected for extraction. At the same time, considering the extraction effect of polar solvents on these three phenolic substances, slightly more polar extraction solvents such as acetone, tetrahydrofuran or ethyl acetate are selected for extraction. The combination of the above two solvents can effectively improve the accuracy of detection.

[0016] Preferably, the volume ratio of the first solvent to the second solvent is (0.8-1.2):(0.8-1.2), wherein the proportion of the first solvent can be 0.8, 0.9, 1, 1.1 or 1.2, etc., wherein the proportion of the second solvent can be 0.8, 0.9, 1, 1.1 or 1.2, etc., but are not limited to the values ​​listed above, and other values ​​not listed within the above numerical range are also applicable.

[0017] Preferably, the liquid-to-solid ratio of the sample to be tested to the organic solvent is 1:(10-40) g / mL, for example 1:10 g / mL, 1:15 g / mL, 1:20 g / mL, 1:25 g / mL, 1:30 g / mL, 1:35 g / mL or 1:40 g / mL, but is not limited to the above-listed values, and other values ​​not listed within the above numerical range are also applicable.

[0018] Preferably, the temperature of the mixing treatment is 40-60°C, such as 40°C, 45°C, 50°C, 55°C or 60°C, but is not limited to the above-listed values. Other values ​​not listed within the above range are also applicable.

[0019] Preferably, the mixing treatment time is 60-120 min, for example 60 min, 70 min, 80 min, 90 min, 110 min, 120 min, etc., but is not limited to the above-listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0020] The above-mentioned specific processing temperature and time can effectively ensure the extraction effect of antioxidants and improve the detection accuracy.

[0021] Preferably, after the filtration, the filtrate is concentrated and then the volume is fixed with an organic solvent.

[0022] Preferably, the chromatographic column for gas chromatography-mass spectrometry detection is a DB-5MS capillary chromatographic column.

[0023] Preferably, the carrier gas for gas chromatography-mass spectrometry detection is helium and / or nitrogen.

[0024] Preferably, the temperature rise program of the gas chromatography-mass spectrometry detection is as follows:

[0025] The initial temperature is 60-100°C, maintained for 0.5-1.5 min, raised to 190-210°C at 10-20°C / min, maintained for 0.1-3 min, then raised to 305-315°C at 25-35°C / min, maintained for more than 8 min.

[0026] The above-mentioned specific detection parameters can effectively improve the accuracy of detection.

[0027] Exemplarily, the ionization mode in the mass spectrometry analysis of the present invention is electron impact ionization (EI), the ion source temperature is 220-235°C, the solvent delay is 3-6 min, the gas-gas interface temperature is 290-305°C, the measurement mode is full scan (SCAN) mode and selected ion (SIM) monitoring mode scanning simultaneously, and the scanning range is 50-600 amu.

[0028] Further, illustratively, the specific parameters of the selected ions in the mass spectrometry analysis of the present invention are: 2,4-bis[(dodecylthio)methyl]-6-methylphenol selected ion (SIM): m / z=97, 111, 168, 202, wherein 97 is a quantitative ion; 2,6-di-tert-butyl-4-ethylphenol selected ion (SIM): m / z=159, 219, 220, 234, wherein 219 is a quantitative ion; 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] selected ion (SIM): m / z=201, 204, 217, 420, wherein 217 is a quantitative ion;

[0029] Selected ion relative abundance ratio: 2,4-bis[(dodecylthio)methyl]-6-methylphenol, with m / z=97 as 100% relative abundance, then: m / z=111 relative abundance is 44.2%~64.2%, m / z=168 relative abundance is 12.8%~42.8%, m / z=202 relative abundance is 42.8%~62.8%; 2,6-di-tert-butyl-4-ethylphenol, with m / z=219 as 100% relative abundance, then: m / z=159 relative abundance is 11. The relative abundance of m / z=220 is 16.8% to 36.8%, and the relative abundance of m / z=234 is 18.7% to 38.7%; for 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], with the relative abundance of m / z=217 as 100%, then: the relative abundance of m / z=201 is 33.4% to 63.4%, the relative abundance of m / z=204 is 45.4% to 65.4%, and the relative abundance of m / z=420 is 7.8% to 37.8%.

[0030] On the other hand, the present invention also provides the application of the above detection method in the detection of food contact materials.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention provides a method for detecting antioxidants in food contact plastic materials or their products. The sample is treated with a specific organic solvent and then subjected to gas chromatography-mass spectrometry detection. The overall method is simple to operate, has low detection limits and quantitative limits, high accuracy, excellent repeatability and reproducibility, and can effectively and accurately detect a variety of phenolic antioxidants at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The total ion current chromatogram of the mixed standard solution of three phenolic substances in Example 1;

[0034] Figure 2 The mass spectrum of 2,4-bis[(dodecylthio)methyl]-6-methylphenol in Example 1;

[0035] Figure 3 The mass spectrum of 2,6-di-tert-butyl-4-ethylphenol in Example 1;

[0036] Figure 4 This is the mass spectrum of 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] in Example 1. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0038] The instruments and equipment used in the following examples are as follows: 7890B GC-5977B MSD gas chromatograph-mass spectrometer, Agilent Technologies (China) Co., Ltd.; XS205 electronic analytical balance, Mettler-Toledo Instrument (Shanghai) Co., Ltd.; CNC ultrasonic cleaner, Kunshan Ultrasonic Instrument Co., Ltd.; vacuum rotary evaporator, Xingyang Kerui Instrument Factory; DB-5MS capillary column (length 30m, inner diameter 0.25mm, thickness 0.25μm, temperature resistance limit: 350℃), Agilent Technologies (China) Co., Ltd.; DB-WAX column (length 30m, inner diameter 0.25mm, thickness 0.25μm, temperature resistance limit: 260℃); DB-1 column (length 30m, inner diameter 0.25mm, thickness 0.25μm, temperature resistance limit: 350℃).

[0039] Standard substances and main reagents: see Table 1 for details.

[0040] Table 1 Standard substances and main reagents

[0041]

[0042] The residual amount of a single phenol additive: 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,6-di-tert-butyl-4-ethylphenol and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] is calculated as follows:

[0043]

[0044] Where:

[0045] X—residue of a single phenolic additive in the sample, in milligrams per kilogram (mg / kg);

[0046] C—Concentration of a single phenolic additive in the sample solution obtained from the standard curve, in micrograms per milliliter (μg / mL);

[0047] C0—the concentration of a single phenolic additive in the blank solution obtained from the standard curve, in micrograms per milliliter (μg / mL);

[0048] V—the fixed volume of the sample solution extract concentrate, in milliliters (mL);

[0049] m—sample mass, in grams (g).

[0050] Example 1

[0051] Qualitative analysis:

[0052] 1) Dissolve and dilute 2,4-bis[(dodecylthio)methyl]-6-methylphenol (labeled as 1), 2,6-di-tert-butyl-4-ethylphenol (labeled as 2) and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] (labeled as 3) standard substances in n-hexane-acetone (volume ratio 1:1) to obtain mixed standard solutions with concentrations of substances 1, 2 and 3 of 10.0 μg / mL, 5.0 μg / mL and 10.0 μg / mL, respectively.

[0053] 2) The standard solution in 1) was separated by DB-5MS capillary column and qualitatively determined by MS.

[0054] In step 2), the instrument parameters are shown in Table 2.

[0055] Table 2 Instrument parameters

[0056]

[0057] Figure 1 This is the total ion current chromatogram of the mixed standard solution of three phenolic substances. Figure 1 It can be seen that the DB-5MS capillary column can effectively separate the three phenolic compounds with good peak shapes.

[0058] Table 3 Qualitative parameters of target substances

[0059]

[0060] Figure 2 , Figure 3 and Figure 4 They are the mass spectra of 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,6-di-tert-butyl-4-ethylphenol and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], and the quantitative and qualitative ions of the target compounds are shown in Table 3.

[0061] Table 4 Maximum allowable deviation of ion relative abundance ratio

[0062] Relative ion abundance% ＞50 ＞20～50 ＞10～20 ≤10 Maximum allowed deviation ±10 ±15 ±20 ±50

[0063] Further, according to Table 4, it can be seen that: 2,4-bis[(dodecylthio)methyl]-6-methylphenol, with m / z=97 as 100% relative abundance, then: m / z=111 relative abundance is 44.2%~64.2%, m / z=168 relative abundance is 12.8%~42.8%, m / z=202 relative abundance is 42.8%~62.8%; 2,6-di-tert-butyl-4-ethylphenol with m / z=219 as 100% relative abundance, then: m / z=159 relative abundance is 11 .1%~31.1%, m / z=220 has a relative abundance of 16.8%~36.8%, and m / z=234 has a relative abundance of 18.7%~38.7%; 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], with the relative abundance of m / z=217 as 100%, then: m / z=201 has a relative abundance of 33.4%~63.4%, m / z=204 has a relative abundance of 45.4%~65.4%, and m / z=420 has a relative abundance of 7.8%~37.8%.

[0064] Drawing of standard curve:

[0065] 1) Accurately weigh 10.0 mg of 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,6-di-tert-butyl-4-ethylphenol and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] standard respectively, dissolve them in n-hexane-acetone (volume ratio 1:1) and make up to 10 mL. The obtained 1000 μg / mL 2,4-bis[(dodecylthio)methyl]-6-methylphenol standard stock solution is named A; the 1000 μg / mL 2,6-di-tert-butyl-4-ethylphenol standard stock solution is named B; the 1000 μg / mL 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol standard stock solution is named C.

[0066] 2) Take 1.0 mL of each of A and C in 1) and dilute to 10 mL with n-hexane-acetone (volume ratio 1:1) to obtain a 100 μg / mL mixed standard working solution of 2,4-bis[(dodecylthio)methyl]-6-methylphenol and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], named A1C1.

[0067] 3) Take 1.0 mL of B1 in 1) and dilute it to 10 mL with n-hexane-acetone (volume ratio 1:1) to obtain a 100 μg / mL 2,6-di-tert-butyl-4-ethylphenol standard working solution, named B1.

[0068] 4) Take 1.0 mL of B1 in 3) and dilute it to 10 mL with n-hexane-acetone (volume ratio 1:1) to obtain a 10 μg / mL 2,6-di-tert-butyl-4-ethylphenol standard working solution, named B2.

[0069] 5) Take 0.01 mL of A1C1 and 0.01 mL of B2, 0.1 mL of A1C1 and 0.1 mL of B2, 0.2 mL of A1C1 and 0.1 mL of B1, 0.5 mL of A1C1 and 0.2 mL of B1, and 1.0 mL of A1C1 and 0.5 mL of B1, respectively, and dilute to 10 mL with n-hexane-acetone (volume ratio 1:1) to obtain 0.1, 1.0, 2.0, 5.0, 10.0 of 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] and 0.01, 0.1, 1.0, 2.0, 5.0 of 2,6-di-tert-butyl-4-ethylphenol mixed standard working solutions.

[0070] 6) GC-MS was used for determination. The instrument parameters are shown in Table 2 and the qualitative parameters are shown in Table 3.

[0071] 7) The standard curves were drawn with the concentrations of the three phenolic substances in the standard working solution as the abscissa and the peak area as the ordinate. The curve equation and correlation coefficient are shown in Table 5.

[0072] Table 5 Standard curves and correlation coefficients of target substances

[0073]

[0074]

[0075] As shown in Table 5, the standard curves of these three phenolic substances have a wide linear range, the correlation coefficients are all greater than 0.999, and the linear relationship is good.

[0076] Example 2

[0077] The steps of this embodiment are basically the same as those of embodiment 1, except that two capillary chromatographic columns, DB-Wax (30m×0.25mm×0.25μm) and DB-1 (30m×0.25mm×0.25μm), are used to analyze the sample. It is found that the three target substances are more strongly retained in DB-1 and elute later. Since the boiling point of 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] is relatively high and the maximum operating temperature of DB-Wax is about 250°C, the low chromatographic column temperature cannot meet the analysis requirements of 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol].

[0078] Furthermore, by comparing Examples 1 and 2, it was found that the most suitable chromatographic column for analyzing the three phenolic antioxidants was the DB-5MS capillary chromatographic column.

[0079] Example 3

[0080] Three standard added samples made of polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC) were selected. The single variable method was used to test the optimal process parameters before testing. The constant factors were the amount of sample to be tested (1.000g±0.01g), extraction method (ultrasonic extraction), and extraction solvent volume (20mL). The variable factors included the type of extraction solvent, extraction temperature, and extraction time.

[0081] Selection of extraction solvent:

[0082] 1) Sample preparation: Cut 10g of PE, PP, and PVC plastic samples into samples with a size of approximately 1cm×1cm;

[0083] 2) Organic solvent extraction: weigh 1.000g±0.01g of the sample to be tested, place it in an ultrasonic extraction bottle, add 0.04mL of 100μg / mL mixed standard solution of three phenolic substances, and then add 20mL of organic solvents n-hexane-acetone (volume ratio of 1:1), n-hexane-tetrahydrofuran (volume ratio of 1:1), n-hexane-ethyl acetate (volume ratio of 1:1), cyclohexane-acetone (volume ratio of 1:1), cyclohexane-tetrahydrofuran (volume ratio of 1:1), cyclohexane-ethyl acetate (volume ratio of 1:1), respectively, cover and seal, place in an ultrasonic extractor, ultrasonicate at 60℃ for 60min, obtain the extract, and perform a blank experiment at the same time;

[0084] 3) Concentration: Filter the extract, evaporate to near dryness at 40°C, make up to 2 mL with the solvent in 2), and filter with a 0.22 μm PTFE filter to obtain the test solution;

[0085] 4) Determination: The sample and blank solution were respectively taken and determined by GC-MS to obtain the concentrations of 2,4-bis[(dodecylthio)methyl]-6-methylphenol (marked as substance 1), 2,6-di-tert-butyl-4-ethylphenol (marked as substance 2) and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] (marked as substance 3). The content of each phenolic substance can be calculated by substituting into the formula, and the spike recovery rate is further calculated. See Table 6.

[0086] Table 6 The recovery test results of three phenolic substances under different combined extraction solvent conditions

[0087]

[0088]

[0089] As can be seen from Table 6, after the three representative plastic materials, such as PE, PP, and PVC, were extracted with a combined extraction solution of n-hexane-acetone, n-hexane-tetrahydrofuran, n-hexane-ethyl acetate, cyclohexane-acetone, cyclohexane-tetrahydrofuran, and cyclohexane-ethyl acetate in a volume ratio of 1:1, the spiked recoveries of 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] had no significant difference, and were all relatively high, reaching about 90%.

[0090] Example 4

[0091] The selection of the extraction solvent in this embodiment is basically the same as that in Example 3: steps 1), 2), 3), and 4), with the only difference being that the extraction solvent in step 2) is n-hexane-acetonitrile (volume ratio 1:1), n-hexane-methanol (volume ratio 1:1), cyclohexane-methanol (volume ratio 1:1), cyclohexane-acetonitrile (volume ratio 1:1), acetone, tetrahydrofuran, ethyl acetate, methanol, and acetonitrile; the spiked recovery results of 2,4-bis[(dodecylthio)methyl]-6-methylphenol (marked as substance 1), 2,6-di-tert-butyl-4-ethylphenol (marked as substance 2), and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] (marked as substance 3) are shown in Table 7.

[0092] Table 7 Spiked recovery test results of three phenolic substances under single extractant conditions

[0093]

[0094]

[0095]

[0096] As can be seen from Table 7, after extraction of three representative materials, such as PE, PP, and PVC with n-hexane-acetonitrile (volume ratio 1:1), n-hexane-methanol (volume ratio 1:1), cyclohexane-methanol (volume ratio 1:1), cyclohexane-acetonitrile (volume ratio 1:1), n-hexane, cyclohexane, acetone, tetrahydrofuran, ethyl acetate, methanol, and acetonitrile, the spiked recoveries of 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] are lower than the results of extraction with the combined extraction solution in Example 3, especially when methanol and acetonitrile are used as extractants, the spiked recoveries of the three phenolic substances are all less than 80%. In addition, methanol and acetonitrile can extract some pigment impurities, which are easy to contaminate the GC-MS analysis instrument. Taking into account the weak polarity characteristics of the three phenolic substances and the interference factors of the matrix effects of various sample materials, the combined extraction solution in Example 3 is more effective as an extraction agent.

[0097] Example 5

[0098] Selection of extraction temperature:

[0099] 1) Sample preparation: Cut 10g of PE, PP, and PVC plastic samples into samples with a size of approximately 1cm×1cm;

[0100] 2) Organic solvent extraction: Weigh 1.000 g ± 0.01 g of the sample to be tested, place it in an ultrasonic extraction bottle, add 0.04 mL of a 100 μg / mL mixed standard solution of three phenolic substances, then add 20 mL of an organic solvent, n-hexane-acetone (volume ratio of 1:1), seal it with a lid, place it in an ultrasonic extractor, and ultrasonicate it at 40°C, 50°C, and 60°C for 60 min to obtain the extract, and perform a blank experiment at the same time;

[0101] 3) Concentration: Filter the extract, evaporate to near dryness at 40°C, make up to 2 mL with the solvent in 2), and filter with a 0.22 μm PTFE filter to obtain the test solution;

[0102] 4) Determination: The sample and blank solution were respectively taken and determined by GC-MS to obtain the concentrations of 2,4-bis[(dodecylthio)methyl]-6-methylphenol (marked as substance 1), 2,6-di-tert-butyl-4-ethylphenol (marked as substance 2) and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] (marked as substance 3). The content of each phenolic substance can be calculated by substituting them into the formula, and the spike recovery results are further calculated, see Table 8.

[0103] Table 8 Spiked recovery test results of three phenolic substances at extraction temperatures of 40℃, 50℃, and 60℃

[0104]

[0105] From the results in Table 8, it can be seen that for three representative plastic materials, such as PE, PP, and PVC, under the conditions of a n-hexane-acetone combined extraction liquid with a volume ratio of 1:1 and an ultrasonic extraction time of 60 min, the extraction temperature range is 40-60°C, and the extraction effect of the target substances increases slightly with increasing temperature, but the change is not obvious. It can be considered that 40°C, 50°C, and 60°C can all meet the analysis requirements of the three phenolic additive residues in plastic products.

[0106] Example 6

[0107] The selection of extraction temperature in this embodiment is basically the same as that in Example 5: steps 1), 2), 3), and 4), with the only difference being that the extraction temperature in step 2) is 20°C, 30°C, 70°C, and 80°C; the spiked recovery results of 2,4-bis[(dodecylthio)methyl]-6-methylphenol (marked as substance 1), 2,6-di-tert-butyl-4-ethylphenol (marked as substance 2), and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] (marked as substance 3) are shown in Table 9.

[0108] Table 9 Spiked recovery test results of three phenolic substances at extraction temperatures of 20℃, 30℃, 70℃, and 80℃

[0109]

[0110] The results in Table 9 show that for three representative plastic materials, such as PE, PP, and PVC, under the conditions of a n-hexane-acetone combined extraction liquid with a volume ratio of 1:1 and an ultrasonic extraction time of 60 min, the extraction effects of the target objects at extraction temperatures of 20°C, 30°C, 70°C, and 80°C are all worse than those in Example 4. In addition, when the temperature is greater than or equal to 70°C, the extraction solvent boils and the sealed ultrasound is likely to cause the extraction bottle to burst. Considering the extraction effect and safety factors, the extraction temperature should not be set too low or too high.

[0111] Example 7

[0112] Selection of extraction time:

[0113] 1) Sample preparation: Cut 10g of PE, PP, and PVC plastic samples into samples with a size of approximately 1cm×1cm;

[0114] 2) Organic solvent extraction: Weigh 1.000 g ± 0.01 g of the sample to be tested, place it in an ultrasonic extraction bottle, add 0.04 mL of a 100 μg / mL mixed standard solution of three phenolic substances, then add 20 mL of an organic solvent, n-hexane-acetone (volume ratio of 1:1), seal it with a lid, place it in an ultrasonic extractor, and ultrasonicate it at 60 ° C for 60 min, 90 min, and 120 min, respectively, to obtain the extract, and perform a blank experiment at the same time;

[0115] 3) Concentration: Filter the extract, evaporate to near dryness at 40°C, make up to 2 mL with the solvent in 2), and filter with a 0.22 μm PTFE filter to obtain the test solution;

[0116] 4) Determination: The sample and blank solution were respectively taken and determined by GC-MS to obtain the concentrations of 2,4-bis[(dodecylthio)methyl]-6-methylphenol (marked as substance 1), 2,6-di-tert-butyl-4-ethylphenol (marked as substance 2) and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] (marked as substance 3). Substituting them into the formula, the content of each phenolic substance can be calculated, and the spike recovery rate results are further calculated, see Table 10.

[0117] Table 10 Spiked recovery test results of three phenolic substances when the extraction time was 60-120 min

[0118]

[0119] From the results in Table 10, it can be seen that the three representative plastic materials, such as PE, PP, and PVC, have good extraction effects under the conditions of a n-hexane-acetone combined extraction solution with a volume ratio of 1:1, an extraction temperature of 60°C, and an extraction time of 60 to 120 minutes. Therefore, the extraction time can be selected to be 60 to 120 minutes.

[0120] Example 8

[0121] The selection of extraction time in this embodiment is basically the same as that in Example 7: steps 1), 2), 3), and 4), with the only difference being that the extraction time in step 2) is 10 min, 30 min, 50 min, and 140 min; the spiked recoveries of 2,4-bis[(dodecylthio)methyl]-6-methylphenol (marked as substance 1), 2,6-di-tert-butyl-4-ethylphenol (marked as substance 2), and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] (marked as substance 3) are shown in Table 11.

[0122] Table 11 Spiked recovery test results of three phenolic agents with extraction time of 10-50min and 140min

[0123]

[0124] From the results in Table 11, it can be seen that the three representative plastic materials, such as PE, PP, and PVC, were extracted with a n-hexane-acetone combination extraction solution with a volume ratio of 1:1, an extraction temperature of 60°C, and an extraction time of 10 to 50 minutes. Due to the insufficient extraction time, the extraction was not sufficient and the extraction effect was poor. When the extraction was performed for 140 minutes, the extraction effect was also poor due to factors such as the volatilization of the extraction solvent.

[0125] By comparing the results of Examples 1 and 3-7, the extraction conditions for determining the residual amounts of three types of phenolic substances in plastic material samples can be optimized: the extraction solvent is a combination mixture of any one of n-hexane and cyclohexane and any one of acetone, tetrahydrofuran and ethyl acetate, the extraction temperature is 40-60°C, and the extraction time is 60-120 min.

[0126] Limit of detection and limit of quantitation:

[0127] 1) Sample preparation: Cut 10g of negative PE plastic sample into test samples with a size of approximately 1cm×1cm;

[0128] 2) Organic solvent extraction: weigh 1.000 g ± 0.01 g of the sample to be tested, place it in an ultrasonic extraction bottle, add 0.01 mL of a mixed standard solution of 10.0 μg / mL 2,4-bis[(dodecylthio)methyl]-6-methylphenol and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], and 1.0 μg / mL 2,6-di-tert-butyl-4-ethylphenol, then add 20 mL of an organic solvent of n-hexane-acetone (volume ratio of 1:1), cover and seal, place in an ultrasonic extractor, and ultrasonicate at 60°C for 60 min to obtain an extract;

[0129] 3) Concentration: Filter the extract, evaporate to near dryness at 40°C, make up to 2 mL with the solvent in 2), and filter with a 0.22 μm PTFE filter to obtain the test solution;

[0130] 4) Determination: Take the above low-concentration spiked samples and measure them 10 times by GC-MS to obtain the concentrations of the three phenolic substances. Substitute them into the formula to calculate the content of each phenolic substance, and calculate the average value and standard deviation s. The detection limit is estimated by the average value plus 3 times the standard deviation, and the quantification limit is estimated by 3 times the detection limit. The detection limit of 2,4-bis[(dodecylthio)methyl]-6-methylphenol and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] can reach 0.06mg / kg, and the quantification limit can reach 0.18mg / kg; the detection limit of 2,6-di-tert-butyl-4-ethylphenol can reach 0.006mg / kg, and the quantification limit can reach 0.018mg / kg.

[0131] Accuracy and Precision:

[0132] The main difference between the accuracy and repeatability precision steps and the detection limit and quantification limit test steps is that three concentration levels of standard solution were added, namely: 10.0 μg / mL of 2,4-bis[(dodecylthio)methyl]-6-methylphenol and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], 1.0 μg / mL 0.02mL of mixed standard solution of 2,6-di-tert-butyl-4-ethylphenol was added with 100.0μg / mL of 2,4-bis[(dodecylthio)methyl]-6-methylphenol and 0.04mL of 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] and 0.02mL of mixed standard solution of 100.0μg / mL of 2,4-bis[(dodecylthio)methyl]-6-methylphenol and 0.1mL of 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] and 0.04mL of mixed standard solution of 100.0μg / mL 2,6-di-tert-butyl-4-ethylphenol; secondly, 6 parallel samples were made for each standard addition sample, and the average recovery rate and relative standard deviation were calculated after determination.

[0133] Steps for reproducibility precision: The spiked samples of the above three concentration levels were reproducibly tested by five laboratories, labeled as Laboratory 1, Laboratory 2, Laboratory 3, Laboratory 4 and Laboratory 5. Each laboratory measured each spiked sample three times, calculated the average value, and then calculated the relative standard deviation of each laboratory's results to evaluate the reproducibility and repeatability.

[0134] Table 12 shows the accuracy and precision of the determination methods for three phenolic substances. It can be seen from Table 12 that the spiked recoveries of the three phenolic substances at low, medium and high concentration levels are all greater than or equal to 85.0%, and the relative deviations are all less than 5.0%. It can be seen that the accuracy and repeatability precision of the method meet the requirements.

[0135] Table 13 shows the inter-laboratory comparison results of three phenolic substances. It can be seen from Table 13 that the relative deviations calculated from the spiked samples at three concentration levels measured by five laboratories are all less than 10.0%, indicating that the reproducibility precision meets the requirements.

[0136] Table 12 Accuracy and precision of three phenolic determination methods

[0137]

[0138] Table 13 Inter-laboratory comparison results of three phenolic substances

[0139]

[0140] Furthermore, in combination with Table 12 and Table 13, it can be seen that the method has high accuracy and good repeatability and reproducibility.

[0141] The method of Example 1 was used to test the residual amounts of three phenolic additives in 10 commercially available food contact plastic materials including polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), polyvinyl chloride (PVC), polystyrene (PS), nylon-6 (PA-6), polycarbonate (PC), polyoxymethylene (POM), polylactic acid (PLA), and polyethylene terephthalate (PET). The test results are shown in Table 14, where ND means not detected, which is less than the detection limit.

[0142] Table 14 Determination results of the residues of three phenolic additives in 10 food contact plastic materials

[0143]

[0144]

[0145] It can be found that the method provided by the present invention can effectively and simultaneously detect three specific phenolic antioxidants in market products, and has excellent technical effects.

[0146] The applicant declares that the present invention uses the above embodiments to illustrate the detection method and application of antioxidants in food contact plastic materials or products thereof, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0147] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0148] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A method for detecting antioxidants in food contact plastic materials or their products, characterized in that: The detection method comprises the following steps: The sample to be tested is mixed with an organic solvent, and then filtered, and the filtrate is subjected to gas chromatography-mass spectrometry detection, and the content of the antioxidant in the sample to be tested is calculated according to the detection result; The antioxidant includes any one of 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,6-di-tert-butyl-4-ethylphenol or 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] or a combination of at least two thereof.

2. The detection method according to claim 1, characterized in that: The food contact plastic material includes any one of polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyvinyl chloride, polystyrene, nylon-6, polycarbonate, polyoxymethylene, polylactic acid or polyethylene terephthalate.

3. The detection method according to claim 1 or 2, characterized in that: The antioxidant is a combination of 2,4-bis[(dodecylthio)methyl]-6-methylphenol, 2,6-di-tert-butyl-4-ethylphenol and 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol].

4. The detection method according to any one of claims 1 to 3, characterized in that: The organic solvent comprises a first solvent and a second solvent, the first solvent comprises n-hexane and / or cyclohexane, and the second solvent comprises any one or a combination of at least two of acetone, tetrahydrofuran or ethyl acetate; Preferably, the volume ratio of the first solvent to the second solvent is (0.8-1.2):(0.8-1.2); Preferably, the solid-liquid ratio of the sample to be tested to the organic solvent is 1:(10-40) g / mL.

5. The detection method according to any one of claims 1 to 4, characterized in that: The temperature of the mixing treatment is 40-60°C; Preferably, the mixing treatment time is 60-120 min.

6. The detection method according to any one of claims 1 to 5, characterized in that: After the filtration, the filtrate is concentrated and then the volume is fixed with an organic solvent.

7. The detection method according to any one of claims 1 to 6, characterized in that: The chromatographic column for gas chromatography-mass spectrometry detection is a DB-5MS capillary chromatographic column.

8. The detection method according to any one of claims 1 to 7, characterized in that: The carrier gas for gas chromatography-mass spectrometry detection is helium and / or nitrogen.

9. The detection method according to any one of claims 1 to 8, characterized in that: The temperature rise program of the gas chromatography-mass spectrometry detection is as follows: The initial temperature is 60-100°C, maintained for 0.5-1.5 min, raised to 190-210°C at 10-20°C / min, maintained for 0.1-3 min, then raised to 305-315°C at 25-35°C / min, maintained for more than 8 min.

10. Use of the detection method according to any one of claims 1 to 9 in the detection of food contact materials.

Images