This study systematically evaluates supercritical CO2 (scCO2) extraction for the decontamination of volatile compounds from post-consumer recycled high-density polyethylene (rHDPE), with a focus on co-solvent effects. Time-resolved extraction revealed that contaminant load strongly influenced removal efficiency, and flakes achieved 15% higher performance than pellets due to thinner morphology and reduced re-embedding. Co-solvent assistance further enhanced efficiency, with p-xylene, ethylbenzene, and cyclohexanone achieving up to 35% improvement compared to neat scCO2. Hansen Solubility Parameter (HSP) analysis indicates that solvent compatibility with HDPE is a necessary but insufficient factor for the enhanced decontamination efficiency, and further molecular descriptor analysis provided additional mechanistic insight, highlighting aromaticity, polarizability, rigidity, and topological complexity as key determinants of enhanced efficiency. Aromatic co-solvents facilitated contaminant release through π-electron delocalization and planar rigidity, while cyclohexanone achieved broad solvation capacity via polar functionality and favorable topological descriptors. These results reveal structure-performance relationships that may inform co-solvent selection and contribute to the understanding of scCO2-based decontamination strategies for rHDPE.

The escalating issue of global plastic pollution necessitates the development of efficient and sustainable recycling technologies, particularly for producing safe, food-contact-grade recycled plastics. Within a circular economy framework, polyethylene terephthalate (PET) holds significant promise due to its excellent recyclability. However, contaminants introduced throughout its lifecycle pose a major challenge, and conventional decontamination methods often involve high energy consumption, thermal degradation risks, or chemical residues. Supercritical carbon dioxide (scCO2) emerges as a promising green alternative, yet a systematic understanding of its efficacy, especially from a molecular structure perspective, is lacking. This study therefore aims to comprehensively evaluate the decontamination performance of scCO2 on PET contaminated with 44 representative contaminants and, crucially, to elucidate the intrinsic relationship between decontamination efficiency and molecular descriptors of the contaminants. The results demonstrated that scCO2 achieved high removal efficiency (>95%) for most contaminants within a short treatment time (<30 min). Correlation analyses of decontamination efficiency with the 126 molecular descriptors as well as the five-solute ESABV descriptor system both revealed that contaminants with high sp3-hybridized carbon content, flexible aliphatic chains, and uniform electrostatic distributions were readily removed, whereas those with aromatic rings, strong hydrogen-bonding propensity, and rigid conformations exhibited lower efficiency. The introduction of ethanol as a cosolvent enhanced the removal of recalcitrant contaminants. Furthermore, scCO2 outperformed conventional vacuum decontamination for over 90% of the substances. This work establishes a critical structure-efficiency relationship, providing a theoretical foundation for optimizing scCO2-based processes to achieve food-grade recycled PET and advance sustainable plastic recycling.

Decontamination of contaminants in recycled polyethylene terephthalate (rPET) plays a crucial role for ensuring the safety of recycled food contact materials in recycling process. An approach based on supramolecular solvents (SUPRASs) extraction was applied in decontamination of volatile organic compounds (VOCs) in rPET. SUPRASs were prepared by nonanol and tetrahydrofuran (THF)/water solution. From the results of single-factor experiment optimization, the optimal extraction conditions were determined to be: 2 mL of nonanol, 10 mL of THF, and 40 min of ultrasonication. Compared to traditional organic solvent extraction and alkaline washing, SUPRASs extraction exhibited superior decontamination efficiency, removing over 95% of artificially added contaminants, attributed to the strong solvation ability of SUPRASs across a broad polarity range. Additionally, SUPRASs extraction demonstrated significant efficacy in decontaminating VOCs of actual rPET samples. Twelve VOCs with high detection frequency in rPET were significantly reduced through decontamination, such as styrene, 2,4-di-tert-butylphenol, and benzophenone, etc. Principal component analysis (PCA) revealed that the VOCs profile of ePET (extracted rPET by SUPRASs) closely resembled that of vPET (virgin PET). In addition, orthogonal partial least squares discriminant analysis (OPLS-DA) indicated the concentrations of five compounds with VIP > 1 in ePET were significantly lower than those in vPET. Both analyses confirmed the decontamination effectiveness of SUPRASs extraction. This study demonstrates the potential of SUPRAS-based extraction as an effective laboratory-scale decontamination strategy for rPET. Further studies are required to address solvent safety, recovery, and process integration before industrial implementation.

The synthesis of nitrogen heteroarenes has a rich history, including many illustrious name reactions. These reactions often involve complex oxidative processes or the need for transition metal catalysts, and the synthesis of different N-heteroarenes typically requires a case-by-case approach. Here, we have discovered the conversion of vicinal alkyl and nitro groups on arenes or alkenes into an array of N-heteroarenes, including indoles and pyrroles. Moreover, our approach also facilitates the synthesis of benzimidazoles from ortho NH-alkyl nitroarenes. This versatile method leverages a redox-neutral aromatization and CO reduction sequence, uniquely utilizing Cs2CO3, and is remarkable for its omission of any transition metals. Our strategy is particularly noteworthy for its exceptional atom, step, and redox efficiency, offering significant advantages for the synthesis of alkaloids that are important in pharmaceutical applications. Extensive experimental and computational studies have allowed us to understand the preferred mechanistic pathways for these heteroarene formations.

The circular economy has driven renewed interest in polyethylene terephthalate (PET) recycling, including recycled PET for food packaging, with a focus on reducing production costs and meeting social development goals. This study presents a novel approach to classifying virgin and recycled PET using an economically viable ultraviolet-visible spectroscopy combined with machine learning algorithms. The results show that Baseline Removal (RMBL) is the optimal preprocessing method for binary classification, and Principal Component Analysis (PCA) combined with Random Forest (RF) is the most effective binary classification model to distinguishes between virgin and 100 % recycled PET. To further improve the capability to detect samples of low recycled content, a multi-classification model was then developed. This approach enables the detection of recycled PET content as low as 10 %, providing a quantitative possibility for the classification. This study demonstrates the effectiveness of this approach and has significant implications for sustainable recycling practices.

Amidst the escalating plastic waste crisis, plastic packaging accounts for a large part. Recycling emerges as pivotal for mitigation. Ensuring the safety and quality of recycled plastics for packaging requires a thorough understanding of the characteristics and potential risks of contaminants that may be present. This study addressed challenges posed by excessive sample weight and polymer matrices affecting accurate quantification using headspace solid-phase micro-extraction (HS-SPME), optimizing a HS-SPME gas chromatography mass spectrometry method for comprehensive volatile compound characterization in polymers. An algorithm was developed to select suitable standards for semi-quantification based on structural similarity, enhancing quantification accuracy. We applied these methods to analyze 65 recycled high-density polyethylene (rHDPE) samples from diverse prior uses, identifying 362 volatile compounds. Notably, alkylbenzenes and alkylnaphthalenes emerge as predominant contaminants, likely stemming from detergent residues, with alkylbenzenes exhibiting higher intensities and alkylnaphthalenes posing elevated risk potentials. Benzophenone, chloroxylenol, and various phthalates were widespread, ranging in concentration from 1.3 to 9.5 mg/kg. Additionally, pesticides e. g., dimethazone and atrazine were found predominantly in samples from non-food bottles. Fragrances like Dlimonene, texanol, and amberonne were frequently detected, with amberonne notably contributing significantly to off-odors in the recycled plastics. These findings underscore the complexity of rHDPE composition, highlight specific contaminants of concern, and provide references for improving the recycling process and ensuring the safety and adaptability of rHDPE for food contact purposes or other high value applications.

The lack of data on chemical contamination in recycled polyethylene terephthalate (rPET) in food contact applications, impedes the legalization of rPET in food contact applications in China. This study offers a comprehensive analysis of contaminants in hot-washed rPET flakes, identifying 1011 compounds. While most substances were detected infrequently, some i.e., bis(2-ethylhexyl) phthalate and mineral oil aromatic hydrocarbons stood out for their relatively high average concentrations. Limonene emerged as the most frequently detected flavorants. Rare genotoxic compounds like safrole and diethyl sulfate were detected at low levels, emphasizing the importance of adopting a conservative evaluation approach. Molecular descriptor analysis guided the proposal of four new surrogates, i.e., dimethyl pentanedioate, 2-tridecanone, bis(2-ethylhexyl) terephthalate, and 2,2-dimethoxy-1,2-diphenylethanone, for challenge tests, aiming to better capture the chemical diversity of rPET contaminants. This research unveils the contamination profile of Chinese rPET and suggests adjustments to evaluation protocols, potentially facilitating its high-value applications and minimizing potential harms.

Poly (glycolic acid) (PGA) is an environmentally friendly, biodegradable polymer commonly utilized in biomedical applications. Due to its high thermal deformation temperature, favorable mechanical properties, and effective gas barrier capabilities, PGA has potential application as food contact materials. However, current regulations do not explicitly involve the use of PGA in food contact applications, particularly the migration of oligomers. The potential migration of oligomers from PGA into food must be carefully considered. In this study, a method of ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF MS) was developed for the determination of PGA oligomers. The migration of oligomers in three distinct scenarios were investigated, i.e. packaging for frozen food, disposable containers with heat packaging for short-term storage, and containers for hot food and beverages. These scenarios were assessed in various food simulants, including acidic foods, non-acidic foods, and alcoholic beverages. The results showed that a total of 21 oligomers in PGA samples are identified, including 12 linear oligomers and 9 cyclic oligomers. Notably, the retention time of these oligomers increases with the increase of number of polymerization units. When PGA was employed as packaging for frozen foods, no oligomers are detected in food simulants containing 4% acetic acid, 10% ethanol, or 50% ethanol. In contrast, a variety of linear and cyclic PGA oligomers are identified in the three food simulants when PGA was used for disposable containers with heat packaging and for hot food and beverages. This is particularly evident for linear oligomers GA5 to GA8 and cyclic oligomers GA6 to GA8. The potential mechanisms underlying the migration and formation of these oligomers can be explained that the non-crystalline regions of PGA are an amorphous state, where ester bonds are prone to gradual hydrolysis, facilitated by the diffusion of water molecules. This hydrolysis leads to the cleavage of chain segments, resulting in the generation of long-chain oligomers. Short-chain oligomers, characterized by lower molecular weights, exhibit a higher tendency to migrate into surrounding solutions, particularly within the non-crystalline regions formed by the degradation of long-chain oligomers. Furthermore, short-chain oligomers can undergo self-reorganization from a disordered to an ordered state, facilitating the formation of both linear and cyclic oligomers. Temperature also significantly influences the formation of PGA oligomers, and elevated temperatures lead to a greater variety of oligomers and increased migration concentrations. Therefore, the migration of PGA oligomers into food should be carefully considered in scenarios involving the storage of acidic foods, non-acidic foods, and alcoholic beverages at high temperature.

To enhance the oxygen barrier properties of polyethylene terephthalate (PET) packaging, oxygen scavengers (OS) are applied to introduce active oxygen-scavenging functionalities. However, OS-related food safety risks and their impact on PET recyclability have received insufficient attention. Here, we systematically assessed safety risks by analyzing the migration of volatile, semi-volatile, non-volatile substances, and inorganic elements from various PET bottles. Six substances (eicosane, heneicosane, 3-tert-butylbenzoic acid, azulene, dimethyl phthalate, and 2-ethoxytetrahydrofuran) showed the possibility to exceed their Threshold of Toxicological Concern (TTC) or reference limits, indicating potential risks. Notably, 2-ethoxytetrahydrofuran was strongly linked to OS. Additionally, the effects of OS on the color of recycled PET were examined, revealing significant color shifts (particularly reductions in L* values and increases in b* values) with higher proportions of recycled resin. Outdoor exposure worsened visual changes, further hindering recycling. Future research should focus on optimizing OS benefits while minimizing risks to ensure safety and recyclability.

The safety assessment of food -contact plastic products is crucial for protecting consumers from potential harmful chemical contaminants. This study investigated novel contaminants and substances of concern in self-heating food containers, focusing on the release of microplastics (MPs) and the migration of volatile organic compounds (VOCs). Using micro -Raman spectroscopy, we simulated actual self-heating condition to determine the abundance, size, and size distribution of released MPs. Results showed MPs abundance ranging from 1.7 x 10 6 to 3.4 x 10 6 particles/L, with an average of 2.4 x 10 6 particles/L, where over 98 % of particles were smaller than 20 mu m. For VOCs migration, we employed direct immersion solid -phase micro -extraction coupled with comprehensive two-dimensional gas chromatograph-tandem quadrupole-time-of-flight mass spectrometry (DISPME-GCxGC-QTOF-MS) under three migration conditions. We identified 41 VOCs, including saturated hydrocarbons, fatty acyls, organoxygen compounds, unsaturated hydrocarbons, benzene derivatives, and phenol ethers. Risk substances such as Dibutyl phthalate, Benzophenone, and 4-Methylbenzophenone were detected in three samples. Semi -quantitative analysis and toxicity classification revealed that the maximum migration of all analytes remained below corresponding limit values, indicating a generally low risk to consumers.

Recycled PET (rPET) is gaining popularity for use in the production of new food contact materials (FCMs) under the context of circular economy. However, the limited information on contaminants in rPET from China and concerns about their potential risk are major obstacles to their use in FCM in China. Fifty-five non-volatile compounds were tentatively identified in 126 batches of hot-washed rPET flakes aimed for food packaging applications in China. Although the 55 substances are not necessarily migratable and may not end up in the contacting media, their presence indicates a need for proper management and control across the value chain. For this reason, the 55 substances prioritized on the basis of level of concerns and in-silico genotoxicity profiler. Among them, dimethoxyethyl phthalate, dibutyl phthalate, bis(2-ethylhexyl) phthalate were classified as level V substances, and Michler's ketone and 4-nitrophenol were both categorized as level V substances and had the genotoxic structure alert, while 2,4,5-trimethylaniline was specified with genotoxic structure alert. The above substances have high priority and may pose a potential risk to human health, therefore special attention should be paid to their migration from rPET. Aside from providing valuable information on non-volatile contaminants present in hot-washed rPET flakes coming from China, this article proposed a prioritization workflow that can be of great help to identify priority substances deserving special attention across the value chain.

The chemical safety of poly (butylene adipate-co-terephthalate) (PBAT) based food contact articles (FCAs) has aroused increasing toxicological concerns in recent years, but the chemical characterization and associated risk assessment still remain inadequate as it fails to elucidate the distribution pattern and discern the potential genotoxic and carcinogenic hazards of the identified substances. Herein, the volatile organic compounds (VOCs) in 50 batches of PBAT-based FCAs of representative categories and 10 batches of PLA and PBAT pellets were characterized, by which 237 VOCs of 10 chemical categories were identified and exhibited characteristic distribution patterns in the chemical spaces derived from their molecular descriptors. Chemical hazards associated with the identified VOCs were discerned by a hazard-driven classification scheme integrating hazard-related knowledge from multiple publicly available sources, and 34 VOCs were found to bear genotoxic or carcinogenic hazards and to feature higher average molecular weight than the other VOCs. Finally, the Risk and hazard quotient (HQ) calculated as the metrics of risk suggested that all identified VOCs posed acceptable risks (Risk<10-4 or HQ < 1), whereas oxolane, butyrolactone, N,N-dimethylacetamide, 2-butoxyethanol, benzyl alcohol, and 1,2,3-trichloropropane posed non-negligible (Risk>10-6) genotoxic or carcinogenic risk and thus should be of prioritized concern to promote the chemical safety of PBAT-based FCAs.

Incorporating spent coffee grounds into single-use drinking straws for enhanced biodegradability also raises safety concerns due to increased chemical complexity. Here, volatile organic compounds (VOCs) present in coffee ground straws (CGS), polylactic acid straws (PLAS), and polypropylene straws (PPS) were characterized using headspace - solid-phase microextraction and migration assays, by which 430 and 153 VOCs of 10 chemical categories were identified by gas chromatography - mass spectrometry, respectively. Further, the VOCs were assessed for potential genetic toxicity by quantitative structure-activity relationship profiling and estimated daily intake (EDI) calculation, revealing that the VOCs identified in the CGS generally triggered the most structural alerts of genetic toxicity, and the EDIs of 37.9% of which exceeded the threshold of 0.15 mu g person -1 d-1, also outnumbering that of the PLAS and PPS. Finally, 14 VOCs were prioritized due to their definite hazards, and generally higher EDIs or detection frequencies in the CGS. Meanwhile, the probability of producing safer CGS was also illustrated. Moreover, it was uncovered by chemical space that the VOCs with higher risk potentials tended to gather in the region defined by the molecular descriptor related to electronegativity or octanol/water partition coefficient. Our results provided valuable references to improve the chemical safety of the CGS, to promote consumer health, and to advance the sustainable development of food contact materials.

The recycling of polyethylene terephthalate (PET) stands as an effective strategy for mitigating plastic pollution and reducing resource waste. The study aimed to investigate the characterization and elimination efficiency of volatile organic compounds (VOCs) present in rPET at various recycling stages using comprehensive twodimensional gas chromatography-quadrupole-time-of-flight-mass spectrometry coupled with chemometrics. The results revealed that 52, 135, 95, 44, and 33 VOCs, mostly classified into three chemical groups, were tentatively identified in virgin - PET (v-PET), cold water washed - rPET (C-rPET), decontaminated - rPET (DrPET), melt-extruded - rPET (M-rPET), and solid-state polycondensation - rPET (S-rPET), respectively. Regarding the VOCs with high and median detection frequencies, fatty acyls showed the highest elimination efficiency (100 % and 92 %), followed by organooxygen compounds (81 % and 99 %), others (97 % and 95 %), and benzene and substituted derivatives (82 % and 95 %) in term of HS-SPME. Following the recycling process, there was a general decrease in the concentration of almost all VOCs, as evidenced by the substantial reduction of o-Xylene, hexanoic acid, octanal, and D-limonene from 18.11, 22.43, 30.74, and 7.41 mg/kg to 0, 0, 3.97, and 0 mg/kg, respectively. However, it was noteworthy that the VOCs identified in the samples were not completely extracted, owing to the limitations of HS-SPME. Furthermore, chemometrics analysis indicated significant discrimination among VOCs from vPET, C-rPET, D-rPET, and M-rPET, while indistinct differences were observed between M-rPET and S-rPET. This study contributes to the enhancement of the recycling process and emphasizes the importance of safeguarding consumer health in terms of elimination of VOCs.

Plastic take-out food containers may release microplastics (MPs) into food and pose a potential risk to food safety and human health. Here, after being subjected to hot water treatment, MPs released from three types of plastic food containers (polypropylene, PP; polyethylene, PE; expanded polystyrene, EPS) were identified by micro-Raman spectroscopy. The results showed that the size of released MPs ranged from 0.8-38 mu m and over 96% MPs were smaller than 10 mu m. Various MPs concentrations were found from the three types of containers, that is, 1.90 x 10(4), 1.01 x 10(5), and 2.82 x 10(6) particles/L on average from PP, PE, and EPS, respectively. Moreover, based on thermal and morphology analysis, we discovered that both relaxations of the polymer chains in the rubbery state and defects caused by processing techniques might contribute to the release of MPs. Thus, such release can be reduced by increasing the thermal stability of the materials and mitigating the defects generated during production.

Microplastics (MPs) are contaminants of emerging concern in food and the food supply chain because they may cause adverse effects to human health. Furthermore, food contact material (FCM) may introduce a huge amount of different MPs into food in the process of using. Micro-Raman spectroscopy is a widely used qualitative technology for MPs determination and analysis due to its high resolution (down to 1 & mu;m). In this study, five brands of plastic (polyethylene, PE)-coated paper cups from different manufacturers were collected and the scenario of using them to drink hot water was simulated, and the water extracts were tested by micro-Raman spectroscopy for MPs determination. Optical images and Raman spectra of particles detected were collected, while their concentration in water extract and size distribution were summarised. The average concentration of MPs found in water extracts from 5 paper cups is 12.93 & PLUSMN; 11.69 x 105 item/L, with particle sizes between 1 and 60 & mu;m (in length). Three types of microplastic particles were characterised by Raman spectra based on polymer spectral library, which are PE, polyamide (PA) and uncertain MP.The morphology of PE films before and after exposure to hot water were observed by SEM imaging. The results indicated the inner coating of virgin film of plastic-coated paper cups had a high surface roughness, which lead to breakages and peeling that produced microplastic particles when exposure to hot water.

Emerging biodegradable food contact materials (FCMs) are omnipresent in food handling and processing. However, similar to conventional FCMs, small molecules can migrate into the food matrix during contact. Extensive evaluation of the migration of chemicals, added intentionally and non-intentionally, from FCMs into food is a crucial step in the safety assessment of such materials. In this study, non-targeted screening was first performed to analyze migrants from poly(butylene adipate-co-terephthalate)/modified starch (PBAT/MFS) FCM using gas chromatography–mass spectrometry and ultra-performance liquid chromatography-Q Exactive Plus Hybrid Quadrupole-Orbitrap mass spectrometer. Sixteen volatile migrants were identified, and 134 non-volatile compounds were screened for dissolution precipitates and food simulants using a self-built and commercially-available databases. The risk ranking for migrants revealed that 13 small molecules had high scores and were assigned as Risk I substances of great concern. Among them, pesticide residues and mycotoxins non-intentionally introduced from MFS blending are of great concern.

为了考察电子烟用棉芯是否释放潜在的风险化学成分而影响人体健康,对棉芯的安全性进行风险评估,利用全二维气相色谱串联四极杆飞行时间高分辨质谱(GC×GC-QTOF-MS)、超高效液相色谱-四极杆飞行时间高分辨质谱(UPLC-QTOF-MS)和电感耦合等离子质谱法(ICP-MS)分别对电子烟用棉芯在使用过程中产生的挥发性、半挥发性、不挥发性有机物和元素进行非靶向筛查,并对检出的化学成分进行风险评估.结果表明:①在两款样品中检出8个类别共72种化学成分,其中大部分为挥发性成分,检出化学成分的质量分数大多在3 mg/kg以下.②对所有检出的化学成分通过安全性关注阈值(SCT值)和界定阈值(QT值)筛选出暴露量较高、可能具有潜在风险的9种有机物和金属元素Ti,进一步与美国FDA等公布的相关数据比对,发现即使是暴露量最高的糠醇、糠醛、二乙醇胺和Ti4种化学成分,其值均远低于健康指导值.风险评估结果表明,筛查出的化学成分的暴露量均远低于健康指导值,无需引起安全关注.

Characterizing the volatile organic compounds (VOCs) in food contact paperboards and clarifying the origins of these VOCs are crucial to ensure the quality of the paperboards. Herein, VOCs present in raw paperboards (RPBs) intended for food contact and related raw materials comprising eucalyptus wood chips (WCs), bleached chemi-thermomechanical pulp (BCTMP), and dry pulp sheets (DPSs), were characterized using headspace solid-phase microextraction comprehensive two-dimensional gas chromatography quadrupole-time-of-flight mass spectrometry, by which 331, 191, 154, and 295 VOCs of 6 chemical categories were identified, respectively. It was found by chemometrics that bleaching significantly impacted the VOCs present in the RPBs and the DPSs in terms of both the number and chemical category of the VOCs, and that the DPSs exhibited higher correlations with the RPBs than other raw materials in terms of the VOCs. Most importantly, 153 VOCs present in the RPBs could be traced to the raw materials due to their co-occurrence, whereas the remaining 178 VOCs were proposed to originate from the RPBs production stage, relating to processing aids (22%), functional additives (17%), degradation products (51%), and contaminants (3%). Our results provided valuable references for the paper industry and were beneficial to promote food safety and the well-being of consumers.

目的 有效考察食品接触用再生聚氯乙烯类材料中氯乙烯、1,1-二氯乙烯和1,1-二氯乙烷的迁移风险.方法 建立测定食品接触用再生聚氯乙烯类材料中氯乙烯、1,1-二氯乙烯和1,1-二氯乙烷在水、酸性、含乙醇、橄榄油和化学替代溶剂中迁移量的气相色谱法.采用DB-624(60 m×250μm×1.4μm)毛细管柱对迁移实验后的3种物质进行组分分离,用电子捕获检测器(ECD)进行检测.结果 氯乙烯、1,1-二氯乙烯和1,1-二氯乙烷的色谱分离效果较好,在0.005～0.05 mg/kg内线性关系良好,检出限为0.001 mg/kg,定量限为0.005 mg/kg.当添加量为0.005、0.01和0.02 mg/kg时,3种物质的加标回收率为94.8％～108％,相对标准偏差(n=6)为0.0％～9.0％,均低于10％.结论 该方法具有较好的精密度和准确度,可用于食品接触用再生聚氯乙烯类材料中氯乙烯、1,1-二氯乙烯和1,1-二氯乙烷迁移量的测定.