Qualitative identification method of small molecule compounds in food contact materials

Abstract

The application discloses a qualitative identification method for small molecule compounds in food contact materials, and belongs to the technical field of food contact material safety detection. The small molecule compounds in the food contact materials are directly enriched by using a solid phase microextraction method, the small molecule compounds adsorbed are desorbed through a thermal desorption action, and then qualitative analysis is conducted by using a GC-MS instrument. The small molecule compound extraction effects under different extraction times and extraction temperatures are investigated.

Description

Technical Field

[0001] This invention belongs to the field of food contact material safety testing technology, specifically relating to a qualitative identification method for small molecule compounds in food contact materials. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] With the development of the times and the increasing awareness of food safety among the public, the safety of food contact materials has gradually attracted widespread attention. Among these, the qualitative identification of small molecule compounds, as potential hazard factors in food contact materials, is particularly important. Currently, scholars both domestically and internationally have achieved certain research results in this field, but many challenges and unresolved issues remain.

[0004] Existing research primarily focuses on the qualitative identification of common small-molecule compounds in food contact materials. Domestic research on food contact materials mainly concentrates on highly toxic compounds such as phthalates, bisphenol A derivatives, primary aromatic amines, and additives. However, research on other potential small-molecule compounds, such as trace additives and residues, is relatively limited. Therefore, future research needs to broaden its scope and comprehensively explore the types and characteristics of small-molecule compounds in food contact materials.

[0005] In addition, most existing technologies use food simulant methods for migration extraction, but these methods generally use organic solvents such as ethanol and n-hexane during extraction. This process involves steps such as extraction, transfer, and concentration, making the entire extraction process cumbersome and inefficient. The extraction, transfer, and concentration processes also result in the loss of some small molecule compounds. Furthermore, the use of organic solvents is not environmentally friendly or economical. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a qualitative identification method for small molecule compounds in food contact materials. This invention primarily focuses on disposable plastic food containers used in takeout packaging, specifically addressing the qualitative identification of low-molecular-weight oligomers precipitated from them.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for qualitative identification of small molecule compounds in food contact materials, comprising the following steps: Place the solid-phase microextraction needle into the holder of the solid-phase microextraction kit and insert it into the headspace vial containing food contact material fragments, then heat and extract. The extracted solid-phase microextraction needle was removed, and the adsorbed small molecule compounds were qualitatively identified using gas chromatography-mass spectrometry.

[0008] One or more of the above technical solutions have the following advantages or beneficial effects: This invention employs solid-phase microextraction (SPE) to directly enrich small molecule compounds in food contact materials. After thermal desorption, the adsorbed small molecule compounds are desorbed and qualitatively analyzed using gas chromatography-mass spectrometry (GC-MS). The extraction efficiency of small molecule compounds at different extraction times and temperatures was investigated.

[0009] The method for identifying small molecule compounds in food contact materials established in this invention can accurately identify and characterize small molecule compounds precipitated from PP and PS plastic food containers. In this invention, when using solid-phase microextraction, the number of precipitated small molecule compounds gradually increases with increasing extraction temperature. Extraction of PP materials under various conditions primarily yields long-chain alkanes, followed by a smaller number of small-molecule compounds at an extraction temperature of 20℃. At 40℃, olefins and esters precipitate after 0.5h, 1.5h, and 2h. At 60℃, esters precipitate under all conditions, while alcohols and olefins precipitate after 1h, 1.5h, and 2h. At 80℃, esters and alcohols precipitate under all conditions, ketones precipitate after 0.5h and 2h, and olefins precipitate after 1h and 1.5h. At 100℃, esters, alcohols, and ketones precipitate under all conditions, olefins precipitate after 0.5h and 2h, and phenol precipitates after 1h and 2h. Due to their strong structural stability and hard texture, PS-type food contact materials require higher temperatures and longer extraction times compared to PP-type food contact materials to extract some small molecule compounds, mainly alkanes, aromatics, and halogenated compounds. Among these, the main alkanes are 2,6,11-trimethyldodecane and tetramethylhexadecane; the main aromatic compounds are trans-1,1'-(1,2-cyclobutadiene)bisbenzene; and the main halogenated compounds are 1-iodo-2-methylundecane and 2-bromononane.

[0010] The method for identifying small molecule compounds in food contact materials established in this invention can accurately identify and characterize small molecule compounds precipitated from PP and PS plastic food containers. Especially for PS food contact materials, due to their good stability and hard texture, it is difficult to extract the corresponding small molecule compounds when using food simulants for extraction. For PP and PS materials, this invention directly uses solid-phase microextraction combined with gas chromatography-mass spectrometry (GC-MS) to detect small molecule compounds, which is more conducive to the qualitative identification of small molecule compounds. Furthermore, the entire process is simple, green, economical, and environmentally friendly. Attached Figure Description

[0011] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0012] Figure 1 The total ion chromatogram is the result of extraction at 20°C for 0.5 h in Example 1.

[0013] Figure 2 The image shows the total ion chromatogram of the extraction at 20°C for 1 hour in Example 1.

[0014] Figure 3 The total ion chromatogram is for the extraction at 20°C for 1.5 hours in Example 1.

[0015] Figure 4 The image shows the total ion chromatogram of the extraction at 20°C for 2 hours in Example 1.

[0016] Figure 5 The total ion chromatogram is shown for the extraction at 40°C and 0.5h in Example 1.

[0017] Figure 6 The image shows the total ion chromatogram of the extraction at 40°C for 1 hour in Example 1.

[0018] Figure 7 The total ion chromatogram is the result of extraction at 40°C for 1.5 hours in Example 1.

[0019] Figure 8 The image shows the total ion chromatogram of the extraction at 40°C for 2 hours in Example 1.

[0020] Figure 9 The total ion chromatogram is shown for the extraction at 60°C for 0.5 h in Example 1.

[0021] Figure 10 The image shows the total ion chromatogram of the extraction at 60°C for 1 hour in Example 1.

[0022] Figure 11 The total ion chromatogram is the result of extraction at 60°C for 1.5 hours in Example 1.

[0023] Figure 12 The image shows the total ion chromatogram of the extraction at 60°C for 2 hours in Example 1.

[0024] Figure 13 The total ion chromatogram is shown for the extraction at 80°C and 0.5h in Example 1.

[0025] Figure 14 The image shows the total ion chromatogram of the extraction at 80°C for 1 hour in Example 1.

[0026] Figure 15The total ion chromatogram is the result of extraction at 80°C for 1.5 hours in Example 1.

[0027] Figure 16 The image shows the total ion chromatogram of the extraction at 80°C for 2 hours in Example 1.

[0028] Figure 17 The total ion chromatogram is shown for the extraction at 100°C for 0.5 h in Example 1.

[0029] Figure 18 The total ion chromatogram is shown for extraction at 100°C for 1 hour in Example 1.

[0030] Figure 19 The total ion chromatogram is shown for the extraction at 100°C for 1.5 hours in Example 1.

[0031] Figure 20 The total ion chromatogram is shown for extraction at 100°C for 2 hours in Example 1.

[0032] Figure 21 The total ion chromatogram is shown for the extraction at 80°C for 1 hour in Example 2.

[0033] Figure 22 The total ion chromatogram is shown for the extraction at 80°C for 2 hours in Example 2.

[0034] Figure 23 The total ion chromatogram is shown for the extraction at 80°C for 4 hours in Example 2.

[0035] Figure 24 The total ion chromatogram is shown for the extraction at 80°C for 8 hours in Example 2.

[0036] Figure 25 The total ion chromatogram is shown for the extraction at 100°C for 1 hour in Example 2.

[0037] Figure 26 The total ion chromatogram is shown for the extraction at 100°C for 2 hours in Example 2.

[0038] Figure 27 The total ion chromatogram is shown for the extraction at 100°C for 4 hours in Example 2.

[0039] Figure 28 The total ion chromatogram is shown for the extraction at 100°C for 8 hours in Example 2. Detailed Implementation

[0040] Existing research on small molecule compounds (such as trace additives and residues) in food contact materials is limited. This invention conducts migration tests on food packaging materials made of plastic products and uses gas chromatography to detect the types and quantities of small molecule compounds in the migration solution, thereby achieving qualitative identification. Research on food safety hazard identification and toxicity mechanisms, migration and transformation patterns of hazardous substances in food raw materials, and safety control mechanisms is of great significance for food safety.

[0041] In one typical embodiment, the present invention provides a method for qualitative identification of small molecule compounds in food contact materials, comprising the following steps: placing a solid-phase microextraction needle into the support of a solid-phase microextraction kit and inserting it into a headspace vial containing food contact material fragments, and heating for extraction; The extracted solid-phase microextraction needle was removed, and the adsorbed small molecule compounds were qualitatively identified using gas chromatography-mass spectrometry.

[0042] In one or more embodiments, the food contact material includes a disposable plastic lunch box, preferably at least one of PP and PS materials. When the food contact material is PP, the heating extraction temperature is 20~100℃, specifically 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, etc.; the heating extraction time is 0.5~2h, specifically 0.5h, 1h, 1.5h, 2h, etc. When the food contact material is PS, the heating extraction temperature is 60~100℃, specifically 60℃, 70℃, 80℃, 90℃, 100℃, etc., preferably 80~100℃; the heating extraction time is 2~8h, specifically 2h, 3h, 4h, 5h, 6h, 7h, 8h, etc.

[0043] In one or more embodiments, food contact material fragments are placed in a headspace vial and sealed. 1-5 g (preferably 1-3 g, most preferably 2 g) of food contact material fragments are placed in a 40 mL headspace vial.

[0044] In one or more embodiments, the chromatographic conditions were as follows: Agilent 19091S-433: 325°C. A 30 m × 250 μm × 0.25 μm capillary column was used. Specifically, an Agilent HP-5 MS column was used, with column stationary phase consisting of "5% phenyl-95% methylpolysiloxane". Helium was used as the carrier gas. The carrier gas flow rate was 0.5–2 mL / min, preferably 0.8–1.2 mL / min, and most preferably 1 mL / min.

[0045] The injection port temperature is 270~290°C, preferably 275~285°C, and more preferably 280°C. To avoid condensation of volatile small molecule compounds, the injection port temperature is generally close to the maximum temperature of the column oven.

[0046] The injection mode is splitless. This invention employs a fully splitless injection process. Initial splitless injection followed by a certain period of splitting is to conserve carrier gas and prevent complex components in the sample matrix from entering the column and contaminating it. This experiment uses headspace analysis to detect small molecule compounds, which do not contaminate the column, thus eliminating the need for subsequent splitting measures.

[0047] The injection volume is 0.5~2μL, preferably 1μL.

[0048] Temperature ramping program: Initial temperature 55~65℃, hold for 1~3 min, then increase to 290~310℃ at a rate of 14~16℃ / min, hold for 4~6 min. Preferably, the temperature ramping program is: Initial temperature 60℃, hold for 2 min, then increase to 300℃ at a rate of 15℃ / min, hold for 5 min.

[0049] In one or more embodiments, the mass spectrometry conditions are: quadrupole temperature, ion source temperature, ion source: EI source, collision energy: 70 eV; and the scanning mode is full scan mode.

[0050] Solid-phase microextraction (SPE) is used to process PS and PP food contact materials. PS materials are mainly composed of aromatic compounds (benzene series, biphenyl, naphthalene derivatives) and nitrogen-containing heterocycles; PP materials are mainly composed of alkanes (straight-chain + branched-chain) and cycloalkanes. Typically, PS materials mainly contain styrene, benzaldehyde, 1,1'-(1,3-propanediyl)bisbenzene, and m-phenylethylbenzonitrile; PP materials typically lack benzene rings and are mainly composed of saturated hydrocarbons. PS materials contain some nitrogen-containing compounds, while PP materials contain very few. Both contain a large amount of haloalkanes. The characteristic of PS lies in its aromatic skeleton; styrene and its derivatives, and nitrogen-containing heterocycles are the most significant features distinguishing it from PP.

[0051] Specifically, the small molecule compounds enriched by solid-phase microextraction in PP food contact materials mainly include the following categories: (1) Alkanes (straight-chain and branched-chain). For example, decane, undecane, dodecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, and eicosane. Alkanes are the most numerous and widely distributed among the precipitated compounds. (2) Cycloalkanes. For example, butylcyclohexane, pentylcyclohexane, hexylcyclohexane, and dicyclohexane. They are more abundant than straight-chain and branched-chain alkanes and may be PP additives or oligomers. (3) Halogenated alkanes. For example, 1-iodo-2-methylundecane, 2-bromododecane, 2-bromononane, and 1-iodononane. They are generally detected at all temperatures and may be residual intermediates. (4) Alcohols, ethers, and esters. For example, 2-hexyl-1-decanol, 2-butyl-1-octanol, and 11-methyldodecanol. (5) Sulfites. For example, hexyltetradecyl sulfite and octadecyl pentyl sulfite. They may be antioxidants or stabilizers. (6) Olefins. For example, 4,6,8-trimethyl-1-nonene and 2,4,6,8-tetramethyl-1-undecene. They may be degradation products of PP plastic components. (7) Other special compounds. For example, 2,6-di-tert-butyl-p-benzoquinone and 2,4-di-tert-butylphenol. They may be degradation products of antioxidants.

[0052] The amount of small molecule compounds precipitated from PP food contact materials increases with increasing temperature. The higher the temperature, the more types and quantities of compounds are extracted, and high-boiling-point and high-molecular-weight substances are released significantly at high temperatures.

[0053] Specifically: The small molecule compounds enriched by solid-phase microextraction in PS food contact materials mainly include the following categories: (1) Aromatic compounds. Such as styrene, benzaldehyde, benzylimine, (1-azidoethyl)benzene, 1,1'-(1,3-propanediyl)bisbenzene, 1,2-dihydro-1-phenylnaphthalene, 1,2,3,4-tetrahydrophenylnaphthalene, cis / trans-1,1'-(1,2-cyclobutadiyl)bisbenzene. Mainly derived from PS monomers, dimers or additives. (2) Nitrogen-containing heterocyclic compounds. Such as 2-pyridinecarboxynitrile, m-phenylethylbenzonitrile, 1-benzylbenzimidazole 3-oxide, 7-methyl-2-phenylbenzimidazole, 5-chloro-4,6-diphenylpyrimidinone, 2,6-pyrazinediamine. May be additives, by-products or foreign contaminants. (3) Alkanes (straight chain, branched chain). For example, decane, dodecane, 2,6-dimethyldecane, 2,6,11-trimethyldodecane, 2,3,5,8-tetramethyldecane, 4,8-dimethylundecane. They may originate from monomers, intermediates or degradation products involved in polymerization. (4) Halogenated alkanes. 1-Iodo-2-methylundecane, 2-bromononane, 1-iodononane, 1-iodotetradecane, 2-bromododecane, 1-iodooctadecane, 2-bromotetradecane. Their sources may be similar to those of PP food contact materials. (5) Alcohols and ethers. 2-Hexyl-1-decanol, 2-butyl-1-octanol, 11-methyldodecanol, hexyloctyl ether, 2-octyl-1-decanol, 2-hexyl-1-dodecanol. Their sources may be similar to those of PP. (6) Esters. Allyl oxalate (nonyl, decyl, pentadecyl), pentadecyl trichloroacetate, hexadecyl trichloroacetate, 2-phenylethyl octanoate, 2-phenylethyl formate. May be plasticizers or additives. (7) Sulfites. Such as dodecyl-2-propyl sulfite, 2-propyl undecyl sulfite. May be antioxidants or stabilizers. (8) Olefins. Such as 4,6,8-trimethyl-1-nonene, 2,4,6,8-tetramethyl-1-undecene, 10-teicosene. May be degradation products of PS plastic components. (9) Other special compounds. Examples include methadone nitroxides, N-benzyloxy-2-methoxycarbonylaziridine, 7-chloro-2,3-dihydro-3-(4-N,N-dimethylaminobenzylmethyl)-5-phenyl-1H-1,4-benzodiazepine-2-one, and 1-(β-D-2,3-O-dibenzoylfuranosyl)-5-fluorouracil. These may originate from intermediates or contamination.

[0054] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0055] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0056] Example 1 1. Experimental Section 1.1 Reagents and Instruments: Gas chromatography-mass spectrometry (GC-MS) system (7890A-5975C, Agilent Technologies, USA); electronic balance ME104E / 02, Mettler Toled, Switzerland; solid-phase microextraction apparatus (Qingdao Zhenzheng Analytical Instruments Co., Ltd.); 20mL headspace vials; commercially available polypropylene (PP) plastic containers.

[0057] 1.2 Sample preparation: Weigh 2.0g of the shredded food contact material (disposable plastic lunch box), put it into a 40mL headspace vial, and seal it with the cap.

[0058] 1.3 Sample preparation: Extraction of small molecule compounds: The solid-phase microextraction needle was placed in the holder of the solid-phase microextraction manual kit and inserted into a 40mL headspace vial containing 2g of food contact material fragments. Extraction was carried out by heating. The extraction temperatures for PP food contact materials were 20℃, 40℃, 60℃, 80℃, and 100℃; the extraction times were 0.5h, 1h, 1.5h, and 2h.

[0059] Identification of molecular compounds: The extracted solid-phase microextraction needle is removed, and gas chromatography-mass spectrometry is used to qualitatively identify the adsorbed small molecule compounds.

[0060] 1.4 GC / MS Analysis Chromatographic conditions: Agilent 19091S-433; 325℃; 30 m × 250 μm × 0.25 μm capillary column; carrier gas: helium; carrier gas flow rate: 1 mL / min; injection port temperature: 280°C; injection mode: splitless; injection volume: 1 μL. Temperature program: initial temperature 60℃, hold for 2 min, then increase to 300℃ at a rate of 15℃ / min, hold for 5 min.

[0061] Mass spectrometry conditions: quadrupole temperature, ion source temperature, ion source: EI source, collision energy: 70 eV; scan mode: full scan mode.

[0062] Example 2 Unlike Example 1, PS-based food contact material is used.

[0063] Accurately weigh a 2.0 gPS food-grade plastic lunchbox, cut it into small pieces, and place it in a 20 mL headspace vial. Insert a solid-phase microextraction needle into the headspace vial and heat for extraction. Extraction times were 1 h, 2 h, 4 h, and 8 h, respectively. Extraction temperatures were 60 °C, 80 °C, and 100 °C, respectively.

[0064] Results and Discussion 1. Results analysis of Example 1: In the pretreatment of PP food contact materials by solid-phase microextraction, different extraction temperatures (20℃, 40℃, 60℃, 80℃, 100℃) and extraction times (0.5h, 1h, 1.5h, 2h) were used for extraction. After extraction, the samples were analyzed by gas chromatography-mass spectrometry (GC-MS). The analysis results are as follows: Analysis at 20℃: When a 2g sample of PP food contact material was extracted at 20℃ for 0.5h, 1h, 1.5h, and 2h, the extracted samples were analyzed using a gas chromatography-mass spectrometry (GC-MS). After excluding chromatographic peaks caused by stationary phase loss, the number of small molecule compounds precipitated was highest at 0.5h and lowest at 2h. Generally, the number of precipitated small molecule compounds decreased with increasing time. This is attributed to the desorption of small molecule compounds volatilized at low temperatures by the SPME extractor head over time. The specific reason requires further investigation. Long-chain alkanes precipitated at both 1.5h and 2h. At 0.5h, more than 10 small molecule compounds, including acids, alcohols, and esters, precipitated; at 1h, more than 6 small molecule compounds, including esters and silanes, precipitated; at 1.5h, more than 9 small molecule compounds precipitated; and at 2h, more than 4 small molecule compounds precipitated.

[0065] Table 1. Types of small molecule compounds (PP) obtained by solid-phase microextraction at 20℃

[0066] Analysis at 40℃: When a 2g sample of PP food contact material was extracted at 40℃ for 0.5h, 1h, 1.5h, and 2h, the extracted samples were analyzed using gas chromatography-mass spectrometry (GC-MS). Long-chain alkanes precipitated under all conditions; alkenes and esters precipitated under 0.5h, 1.5h, and 2h conditions. More than 52 small molecule compounds precipitated under 0.5h, more than 16 small molecule compounds under 1h, more than 14 small molecule compounds under 1.5h, and more than 44 small molecule compounds under 2h.

[0067] Table 2. Types of small molecule compounds (PP) precipitated at 40℃

[0068] 60℃ Analysis When a 2g sample of PP food contact material was extracted at 60℃ for 0.5h, 1h, 1.5h, and 2h, the extracted samples were analyzed using gas chromatography-mass spectrometry (GC-MS). Long-chain alkanes and esters precipitated under all conditions; alcohols and alkenes precipitated under 1h, 1.5h, and 2h conditions. More than 43 small molecule compounds precipitated under the 0.5h condition; more than 48 small molecule compounds under the 1h condition; more than 49 small molecule compounds under the 1.5h condition; and more than 47 small molecule compounds under the 2h condition.

[0069] Table 3. Types of small molecule compounds (PP) precipitated at 60℃ for 0.5h or 1h.

[0070] Table 4. Types of small molecule compounds (PP) precipitated at 60℃ for 1.5h or 2h.

[0071] 80℃ Analysis When a 2g sample of PP food contact material was extracted at 80℃ for 0.5h, 1h, 1.5h, and 2h, the extracted samples were analyzed using gas chromatography-mass spectrometry (GC-MS). Long-chain alkanes, esters, and alcohols precipitated under all conditions; ketones precipitated under 0.5h and 2h conditions; and olefins precipitated under 1h and 1.5h conditions. More than 69 small molecule compounds precipitated under 0.5h, more than 59 small molecule compounds under 1h, more than 50 small molecule compounds under 1.5h, and more than 61 small molecule compounds under 2h.

[0072] Table 5. Types of small molecule compounds (PP) precipitated at 80℃ for 0.5h or 1h.

[0073] Table 6. Types of small molecule compounds (PP) precipitated at 80℃ for 1.5h or 2h.

[0074] 100℃ Analysis When a 2g sample of PP food contact material was extracted at 100℃ for 0.5h, 1h, 1.5h, and 2h, the extracted samples were analyzed using gas chromatography-mass spectrometry (GC-MS). Long-chain alkanes, esters, alcohols, and ketones precipitated under all conditions; olefins precipitated under 0.5h and 2h conditions; and phenols precipitated under 1h and 2h conditions. More than 58 small molecule compounds precipitated under 0.5h, more than 71 small molecule compounds under 1h, more than 71 small molecule compounds under 1.5h, and more than 72 small molecule compounds under 2h.

[0075] Table 7. Types of small molecule compounds (PP) precipitated at 100℃ for 0.5h or 1h.

[0076] Table 8. Types of small molecule compounds (PP) precipitated at 100℃ for 1.5h or 2h.

[0077] Analysis of the results of Example 2: No small molecule compounds were detected at an extraction temperature of 60℃. Small molecule compounds were detected at 80℃ and 100℃, as detailed below.

[0078] The small molecule compounds precipitated after treatment at 80℃ are shown in the table below (PS type).

[0079] Table 9. Types of small molecule compounds (PS) precipitated from plastic lunch boxes at 80 degrees Celsius.

[0080] The small molecule compounds precipitated after treatment at 100℃ are shown in the table below (PS type).

[0081] Table 10. Types of small molecule compounds (PS) precipitated from plastic lunch boxes at 100 degrees Celsius.

[0082] In summary, the research conclusions of this invention include the following: 1. Solid-phase microextraction for treating PP food contact materials: When using solid-phase microextraction, the number of small molecule compounds precipitated gradually increases with increasing extraction temperature.

[0083] Extraction analysis of PP materials under various conditions revealed that the majority of precipitates were long-chain alkanes. Besides alkanes: at an extraction temperature of 20℃, the number of precipitated small molecule compounds was relatively small; at an extraction temperature of 40℃, olefins and esters precipitated at 0.5h, 1.5h, and 2h; at an extraction temperature of 60℃, esters precipitated under all conditions, and alcohols and olefins precipitated at 1h, 1.5h, and 2h; at an extraction temperature of 80℃, esters and alcohols precipitated under all conditions, ketones precipitated at 0.5h and 2h, and olefins precipitated at 1h and 1.5h; at an extraction temperature of 100℃, esters, alcohols, and ketones precipitated under all conditions; olefins precipitated at 0.5h and 2h; and phenol precipitated at 1h and 2h.

[0084] Table 11. Variation of small molecule compounds under different extraction conditions

[0085] At the same extraction time, the number of precipitated small molecule compounds increases with increasing extraction temperature. Taking 2 hours as an example, as the extraction temperature increases from 20℃ to 100℃, the number of precipitated small molecule compounds increases from 4 to 72. At the same extraction temperature, the number of precipitated small molecule compounds generally increases with increasing extraction time. Overall, 100℃ for 2 hours yields the most types of small molecule compounds (72), while 20℃ for 2 hours yields the fewest (4). Therefore, it can be concluded that the number of precipitated small molecule compounds increases with increasing extraction time and temperature.

[0086] Characteristics of solid-phase microextraction for treating precipitated compounds in PP food contact materials: The results show that the small molecule compounds enriched by solid-phase microextraction in PP food contact materials mainly include the following categories: (1) Alkanes (straight-chain and branched-chain). For example, decane, undecane, dodecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, and eicosane. Alkanes are the most numerous and widely distributed among the precipitated compounds. (2) Cycloalkanes. For example, butylcyclohexane, pentylcyclohexane, hexylcyclohexane, and dicyclohexane. They are more abundant than straight-chain and branched-chain alkanes and may be PP additives or oligomers. (3) Halogenated alkanes. For example, 1-iodo-2-methylundecane, 2-bromododecane, 2-bromononane, and 1-iodononane. They are generally detected at all temperatures and may be residual intermediates. (4) Alcohols, ethers, and esters. For example, 2-hexyl-1-decanol, 2-butyl-1-octanol, and 11-methyldodecanol. They may be plasticizers, lubricants, or additives. (5) Sulfite esters. For example, hexyltetradecyl sulfite and octadecyl pentyl sulfite. These may be antioxidants or stabilizers. (6) Olefins. For example, 4,6,8-trimethyl-1-nonene and 2,4,6,8-tetramethyl-1-undecene. These may be degradation products of PP plastic components. (7) Other special compounds. For example, 2,6-di-tert-butyl-p-benzoquinone and 2,4-di-tert-butylphenol. These may be degradation products of antioxidants.

[0087] Migration behavior of PP food contact materials treated by solid phase microextraction: According to the data in the table, the number of small molecule compounds precipitated in PP food contact materials increases with increasing temperature. The higher the temperature, the more types and quantities of compounds are extracted. High-boiling-point and high-molecular-weight substances are released significantly at high temperatures.

[0088] 2. Enrichment of PS-based food contact materials using solid-phase microextraction: Characteristics of solid-phase microextraction for treating precipitated compounds in PS-based food contact materials: The results show that the small molecule compounds enriched by solid-phase microextraction in PS food contact materials mainly include the following categories: (1) Aromatic compounds. Such as styrene, benzaldehyde, benzylimine, (1-azidoethyl)benzene, 1,1'-(1,3-propanediyl)bisbenzene, 1,2-dihydro-1-phenylnaphthalene, 1,2,3,4-tetrahydrophenylnaphthalene, cis / trans-1,1'-(1,2-cyclobutadiyl)bisbenzene. Mainly derived from PS monomers, dimers or additives. (2) Nitrogen-containing heterocyclic compounds. Such as 2-pyridinecarboxynitrile, m-phenylethylbenzonitrile, 1-benzylbenzimidazole 3-oxide, 7-methyl-2-phenylbenzimidazole, 5-chloro-4,6-diphenylpyrimidinone, 2,6-pyrazinediamine. May be additives, by-products or foreign contaminants. (3) Alkanes (straight chain, branched chain). For example, decane, dodecane, 2,6-dimethyldecane, 2,6,11-trimethyldodecane, 2,3,5,8-tetramethyldecane, 4,8-dimethylundecane. These may originate from monomers, intermediates, or degradation products involved in polymerization. (4) Halogenated alkanes. 1-Iodo-2-methylundecane, 2-bromononane, 1-iodononane, 1-iodotetradecane, 2-bromododecane, 1-iodooctadecane, 2-bromotetradecane. Their sources may be similar to those of PP food contact materials. (5) Alcohols and ethers. 2-Hexyl-1-decanol, 2-butyl-1-octanol, 11-methyldodecanol, hexyloctyl ether, 2-octyl-1-decanol, 2-hexyl-1-dodecanol. Their sources may be similar to those of PP. (6) Esters. Allyl oxalate (nonyl, decyl, pentadecyl), pentadecyl trichloroacetate, hexadecyl trichloroacetate, 2-phenylethyl octanoate, 2-phenylethyl formate. May be plasticizers or additives. (7) Sulfites. Such as dodecyl-2-propyl sulfite, 2-propyl undecyl sulfite. May be antioxidants or stabilizers. (8) Olefins. Such as 4,6,8-trimethyl-1-nonene, 2,4,6,8-tetramethyl-1-undecene, 10-teicosene. May be degradation products of PS plastic components. (9) Other special compounds. Examples include methadone nitroxides, N-benzyloxy-2-methoxycarbonylaziridine, 7-chloro-2,3-dihydro-3-(4-N,N-dimethylaminobenzylmethyl)-5-phenyl-1H-1,4-benzodiazepine-2-one, and 1-(β-D-2,3-O-dibenzoylfuranosyl)-5-fluorouracil. These may originate from intermediates or contamination.

[0089] Solid-phase microextraction method for treating migration behavior of PS food contact materials PS (polystyrene) food contact materials exhibit better thermal stability than PP (polypropylene) food contact materials. Styrene, benzaldehyde, biphenyls, naphthalene derivatives, and nitrogen-containing heterocyclic compounds are the most significant distinguishing features between PS and PP. These compounds originate from PS monomer residues, dimers, additives, or degradation products. At 80℃, typical PS monomers such as styrene and benzaldehyde, along with degradation products, are present; alkanes, halogenated alkanes, and nitrogen-containing heterocyclic compounds are also present. With prolonged exposure time (4h, 8h), more complex aromatic compounds appear. When the temperature rises to 100℃, the release of aromatic compounds and nitrogen-containing heterocyclic compounds from PS materials increases significantly, and pharmaceutical impurities also appear.

[0090] 3. Comparison of migration behavior of PS and PP food contact materials treated by solid phase microextraction. Dominant compound types: PS compounds are mainly aromatic compounds (benzene series, biphenyl, naphthalene derivatives) and nitrogen-containing heterocycles; PP compounds are mainly alkanes (straight chain + branched chain) and cycloalkanes.

[0091] Typical compound characteristics: PS compounds are mainly composed of styrene, benzaldehyde, 1,1'-(1,3-propanediyl)bisbenzene, and m-phenylethylbenzonitrile; PP compounds typically lack benzene rings and are mainly saturated hydrocarbons. PS compounds contain some nitrogen-containing compounds, while PP compounds contain very few; both contain large amounts of haloalkanes.

[0092] PS is characterized by its aromatic skeleton, and styrene and its derivatives, as well as nitrogen-containing heterocycles, are the most significant features that distinguish it from PP.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for qualitative identification of small molecule compounds in food contact materials, characterized in that, The solid-phase microextraction method is used for processing, specifically including the following steps: Place the solid-phase microextraction needle into the holder of the solid-phase microextraction kit and insert it into the headspace vial containing food contact material fragments, then heat and extract. The extracted solid-phase microextraction needle was removed, and the adsorbed small molecule compounds were qualitatively identified using gas chromatography-mass spectrometry.

2. The qualitative identification method according to claim 1, characterized in that, Food contact materials include disposable plastic food containers.

3. The qualitative identification method according to claim 2, characterized in that, The food contact material is at least one of PP material and PS material.

4. The qualitative identification method according to claim 1, characterized in that, Place food contact material fragments into a headspace vial and seal; place 1-5g of food contact material fragments into a 40mL headspace vial.

5. The qualitative identification method according to claim 1, characterized in that, When the food contact material is PP, the heating extraction temperature is 20~100℃; the heating extraction time is 0.5~2h. Alternatively, when the food contact material is PS, the heating extraction temperature is 60~100℃, preferably 80~100℃; the heating extraction time is 2~8h.

6. The qualitative identification method according to claim 1, characterized in that, Chromatographic conditions: Agilent 19091S-433: 325℃: A 30 m × 250 μm × 0.25 μm capillary column was used; The carrier gas is helium; The carrier gas flow rate is 0.5~2 mL / min, preferably 0.8~1.2 mL / min, and most preferably 1 mL / min; The injection port temperature is 270~290°C, preferably 275~285°C, and more preferably 280°C; The injection mode is splitless; The injection volume is 0.5~2μL, preferably 1μL; The temperature program in chromatography is as follows: initial temperature 55~65℃, hold for 1~3 min, then increase to 290~310℃ at a rate of 14~16℃ / min, hold for 4~6 min; preferably, the temperature program is as follows: initial temperature 60℃, hold for 2 min, then increase to 300℃ at a rate of 15℃ / min, hold for 5 min.

7. The qualitative identification method according to claim 1, characterized in that, Mass spectrometry conditions: quadrupole temperature, ion source temperature, ion source: EI source, collision energy: 70 eV; scan mode: full scan mode.

8. The qualitative identification method according to claim 1, characterized in that, Solid-phase microextraction is used to process PS and PP food contact materials, where PS mainly consists of aromatic compounds and nitrogen-containing heterocycles; preferably, the aromatic compounds include benzene series compounds, biphenyls, and naphthalene derivatives. PP compounds are mainly composed of alkanes and cycloalkanes.

9. The qualitative identification method according to claim 1, characterized in that, The small molecule compounds enriched by solid-phase microextraction in PP food contact materials mainly include the following categories: (1) Alkanes; (2) Cycloalkanes; (3) Halogenated alkanes; (4) Alcohols, ethers, and esters; (5) Sulfites; (6) Olefins; (7) Other special compounds; Preferably, other specific compounds include 2,6-di-tert-butyl-p-benzoquinone, 2,4-di-tert-butylphenol, or antioxidant degradation products.

10. The qualitative identification method according to claim 1, characterized in that, The small molecule compounds enriched by solid-phase microextraction in PS-type food contact materials mainly include the following categories: (1) Aromatic compounds; (2) Nitrogen-containing heterocyclic compounds; (3) Alkanes; (4) Halogenated alkanes; (5) Alcohols and ethers; (6) Esters; (7) Sulfites; (8) Olefins; (9) Other special compounds; preferably, other special compounds include methadone nitrides, N-benzyloxy-2-methoxycarbonylaziridine, 7-chloro-2,3-dihydro-3-(4-N,N-dimethylaminobenzylmethyl)-5-phenyl-1H-1,4-benzodiazepine-2-one, 1-(β-D-2,3-O-dibenzoylfuranosyl)-5-fluorouracil, or derived from intermediates or contaminants.

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