用X-射线衍射法测定聚对苯二甲酸乙二醇酯/聚对苯二甲酸丁二醇酯共混体系的结晶度

结晶度是表征聚合物性质的重要参数,它对聚合物的物理和机械性能有很大影响,在测定聚合物的结晶度的各种方法中,X-射线衍射法的意义明确且应用最为广泛。然而,用X-射线衍射法测定聚合物结晶度绝大部分只限于单组份体系,用于共混体系的报道尚不     

聚(对苯二甲酸-1,3-丙二酯)环状低聚物的合成、表征和开环聚合反应

探索了由对苯二甲酰氯和1,3-丙二醇在“假高稀”条件下合成聚(对苯二甲酸-1,3-丙二酯)(PTT)环状低聚物的可行性.通过柱色谱分离了环状低聚物和线形低聚物;用核磁共振、质谱和元素分析表征了产物的化学结构;用GPC和HPLC研究了不同大小环的分布,发现在本文实验条件下合成的PTT环状低聚物主要由二、三、四、五和七聚体构成,其中环状三聚体含量最多,没有发现环状六聚体的存在.PTT环状低聚物的熔程为92.3～222.6℃,熔融后是无色、透明的低粘度液体.于250℃将PTT环状低聚物分别在辛酸亚锡、1-乙基-3-氯四丁基锡氧烷、钛酸四丁酯和三氧化二锑催化下进行开环聚合反应,制备了特性粘数为0.18～0.49dL/g的聚合物.     

基于UPLC-QTOF MS的食品接触用回收PET中非挥发性有机物的非靶向筛查

采用超高效液相色谱－串联四极杆飞行时间质谱技术（UPLC－QTOF MS）对经初步清洗后的回收聚对苯二甲酸乙二醇酯（rPET）瓶片中潜在的非挥发性有机物进行非靶向筛查,并考察了不同沉淀溶剂、去除溶剂方式、测试样品量等前处理方法,以及不同测试方法、流动相及洗脱剂梯度等条件对rPET瓶片中非挥发性有机物测定的影响。研究结果显示：以0.2 g的rPET瓶片溶于10 mL六氟异丙醇中,20 mL甲醇作为沉淀溶剂、氮吹去除溶剂的前处理方式,以甲醇－0.1%甲酸水体系作为流动相梯度洗脱,采用数据依赖型采集（DDA）模式进行测试。此时获得方法的回收率为66.0%～80.4%,相对标准偏差（RSD）均不高于5.1%,表现出较好的稳定性和可重复性。采用质谱数据库和二级谱图定性,通过结构类似的化合物进行半定量,rPET瓶片中共检出30种非挥发性有机化合物,含量范围为0.038～4.92 mg/kg。检出物质包括环状和线型寡聚物、助剂副产物或降解产物和污染物等非有意添加物27种,其余3种可能是有意添加物。利用建立的非靶向筛查方法以及主成分分析（PCA）对两个不同地域厂家的24种rPET瓶片（rPET C和rPET N）进行检测,结果显示两组样品在正离子模式下有明显差异,检出差异物质15种;负离子模式下差异不明显。表明同类型但不同来源的rPET瓶片具有不同的差异物质。研究表明,所建立的UPLC－QTOF MS筛查方法具有准确可靠、简单、快速等优点,可有效用于食品接触rPET中非挥发性有机物的分析及安全评价工作     

Migration Modeling as a Valuable Tool for Exposure Assessment and Risk Characterization of Polyethylene Terephthalate Oligomers

Polyethylene terephthalate (PET) is one of the most widely used food contact materials due to its excellent mechanical properties and recyclability. Migration of substances from PET and assessment of compliance are usually determined by experimental testing, which can be challenging depending on the migrants of interest. Low concentrations and missing reference standards, among other factors, have led to inadequate investigation of the migration potential of PET oligomers. Migration modeling can overcome such limitations and is therefore a suitable starting point for exposure and risk assessment. In this study, the activation energy-based (E_A) model and the A_P model were used to systematically evaluate the migration potential of 52 PET oligomers for 12 different application scenarios. Modeling parameters and conditions were evaluated to investigate their impact and relevance on the assessment of realistic exposures. Obtained results were compared with safety thresholds known from the concept of toxicological thresholds of concern. This allowed the evaluation and identification of oligomers and/or applications where migration or exposure levels may be associated with a potential risk because they exceed these safety thresholds. Overall, this study demonstrated that migration modeling can be a high-throughput, fast, flexible, and suitable approach for comprehensive exposure assessment.     

Dissipation and Residue of Metalaxyl-M and Azoxystrobin in Scallions and Cumulative Risk Assessment of Dietary Exposure to Hepatotoxicity

Metalaxyl-M and azoxystrobin have been used to control various fungal diseases on scallion and other crops. In view of the adverse toxic effects of both on the mammalian liver, it is necessary to conduct a cumulative risk assessment of their dietary exposure to consumers. The residues of metalaxyl-M and azoxystrobin on scallion were determined by a quick, easy, cheap, effective, rugged, and safe method (QuEChERS) combined with high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS). The half-lives were about 1.15 and 3.89 days, respectively, and the final residues after a seven-day harvest interval were <0.001–0.088 mg/kg and 0.190–4.687 mg/kg, respectively. The cumulative dietary risk quotient of the two fungicides to Chinese consumers calculated by the probability model is 13.94%~41.25%. According to the results of the contribution analysis, the risk posed by azoxystrobin is much greater than that of metalaxyl-M. Although metalaxyl-M and azoxystrobin do not pose a cumulative risk to Chinese consumers, the risk to children and adolescents is significantly higher than that to adults. This suggests that in future research, more consideration should be given to the cumulative risk of compounds to vulnerable groups.     

Impact of Partitioning in Short-Term Food Contact Applications Focused on Polymers in Support of Migration Modelling and Exposure Risk Assessment

Food contact materials (FCMs) can transfer chemicals arising from their manufacture to food before consumption. Regulatory frameworks ensure consumer safety by prescribing methods for the assessment of FCMs that rely on migration testing either into real-life foods or food simulants. Standard migration testing conditions for single-use FCMs are justifiably conservative, employing recognized worst-case contact times and temperatures. For repeated-use FCMs, the third of three consecutive tests using worst-case conditions is taken as a surrogate of the much shorter contact period that often occurs over the service life of these items. Food contact regulations allow for the use of migration modelling for the chemicals in the FCM and for the partitioning that occurs between the FCM and food/simulant during prolonged contact, under which steady-state conditions are favored. This study demonstrates that the steady-state is rarely reached under repeated-use conditions and that partitioning plays a minor role that results in migration essentially being diffusion controlled. Domains of use have been identified within which partitioning does not play a significant role, allowing modelling based upon diffusion parameters to be used. These findings have the potential to advance the modelling of migration from repeated-use articles for the benefit of regulatory guidance and compliance practices.     

不同拉伸比PET／PBT共混纤维的热行为及力学性能

不同拉伸比ＰＥＴ／ＰＢＴ共混纤维的热行为及力学性能尹秀丽（天津纺织工学院材料科学系天津３００１６０）关键词聚对苯二甲酸乙二醇酯，聚对苯二甲酸丁二醇酯，共混纤维，热行为，力学性能不同配比聚对苯二甲酸乙二醇酯（ＰＥＴ）／聚对苯二甲酸丁二醇酯（ＰＢＴ）共混...     

PET,PBT结晶过程Avrami方程的探讨

用解偏振光法研究了PET,PBT以及PET-PBT,PBT-PBI共聚物在不同条件下的等温结晶过程.结果表明,Avrami指数n值和结晶速度常数随条件不同呈明显规律变化,且n值在绝大多数情况下不成整数.由此提出了这样的假设:n值是一个与晶核中结晶生长点数目相关的参数.     

桃中农药残留分析及膳食暴露评估研究

为明确并量化食用桃途径的农药膳食摄入风险水平,通过对19个桃主产区采集的98份样品进行农药残留检测,对桃中的农药残留急/慢性膳食摄入风险进行评估,并借鉴英国兽药残留委员会兽药残留风险排序矩阵进行农药和样品风险排序。结果在桃中检出了38种农药残留,98个样品的检出率为95.9%,检出的农药含量为0.007 4～3.399 3 mg/kg;检出农药的慢性膳食摄入风险(%ADI)和急性膳食摄入风险(%ARfD)的平均值分别为0.89%和11.09%,风险均低于100%,不会对人体产生慢性或急性风险;风险排序结果表明桃果品中氟虫腈、硫丹、灭多威、丁硫克百威、毒死蜱、联苯菊酯为6种为高风险农药,应在生产和质量安全监管中予以重点关注。该文为桃安全消费、农药残留监管和农药最大残留限量(MRLs)制修订提供了科学依据。     

Investigation and Analysis of Pesticide Residues in Four Common Vegetables and Risk Assessment of Dietary Exposure in Ceramic Capital,China

In order to understand the basic situation of pesticide residues in vegetables in China’s porcelain capital, four kinds of common vegetables on the market were selected in this study for detection and analysis of pesticide residues. The pesticide residues in vegetables were analyzed through sample selection, optimization of instrument and equipment conditions, and comparison of detection pass rates. The sampling locations were common vegetables purchasing places such as large and medium-sized supermarkets. QuEChERS method was used as the sample pretreatment, and gas chromatography (GC-MS/MS) was used for quantitative analysis. Finally, the exposure risk of pesticides was assessed according to the test results. The results showed that all the pesticides were detected in four kinds of vegetables, but the detected pesticides did not exceed the national standard (GB 2763-2014, China). Moreover, the target risk coefficient (THQ) and risk index (HI) values of four vegetables were less than one, indicating that the combined and toxic effect of pesticide residual mixed contamination was smaller in four vegetables. Therefore, there was no significant harm from people using these vegetables.     

Fast Detection of Cadmium in Chocolate by Solid Sampling Electrothermal Vaporization Atomic Absorption Spectrometry and Its Application on Dietary Exposure Risk Assessment

In this work, a rapid detection method using solid sampling electrothermal vaporization atomic absorption spectrometry (SS-ETV-AAS) was established for cadmium in chocolate. The instrumental system includes a solid sampling ETV unit, a catalytic pyrolysis furnace, an AAS detector, and a gas supply system with only an air pump and a hydrogen generator. Herein, MgO material with 1.0–1.5 mm particle size was first employed to replace the kaolin filler previously used to further shorten the peak width and to thereby improve the sensitivity. With 350 mL/min of air, a chocolate sample was heated for 25 s from 435 to 464 °C to remove water and organic matrices; then, after supplying 240 mL/min hydrogen and turning down air to 120 mL/min, a N₂/H₂ mixture gas was formed to accelerate Cd vaporization from chocolate residue under 465 to 765 °C. Under the optimized conditions, the detection limit (LOD) was obviously lowered to 70 pg/g (vs. previous 150 pg/g) with R² > 0.999; the relative standard deviations (RSD) of repeated measurements for real chocolate samples ranged from 1.5% to 6.4%, indicating a favorable precision; and the Cd recoveries were in the range of 93–107%, proving a satisfied accuracy. Thus, the total analysis time is less than 3 min without the sample digestion process. Thereafter, 78 chocolate samples with different brands from 9 producing countries in China market were collected and measured by this proposed method. Based on the measured Cd concentrations, a dietary exposure assessment was performed for Chinese residents, and the target hazard quotient (THQ) values are all less than 1, proving no significant health risk from intaking chocolate cadmium for Chinese residents.     

Dissipation and Dietary Risk Assessment of Pydiflumetofen Residues in Soybean

In this study, the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, combined with high-performance liquid chromatography–tandem mass spectrometry, was chosen for detecting pydiflumetofen residues in soybean plants, soybeans and soil, and assessing the risk of short- and long-term dietary intake. Pydiflumetofen concentrations ranging from 0.001–0.5 mg/L exhibited good linearity (r > 0.997). At varying doses, the average pydiflumetofen recovery rates and relative standard deviations among soybean plants, soybeans, and soil ranged from 83.9 ± 1.1% to 99.5 ± 3.3% and from 0.77 to 7.77%, respectively. The sensitivity, accuracy, and precision of the chosen methodology met the requirements of pesticide residue analysis. The results of the degradation dynamics test showed that the half-life of pydiflumetofen (t_1/2) in soybean plants and in soil were 3.6 to 5.7 and from 7.9 to 25.7 d, respectively. Assessment of the concentration of pydiflumetofen residues in soybeans revealed acute and chronic dietary exposure risks of 0.06 and 7.54%, respectively. As these values are very low, pydiflumetofen residues in soybeans present an acceptable risk to public health. The results of this study will help to guide the practical application of pydiflumetofen and minimize the environmental risks associated with its use.     

基于全链条的回收PET材料中非挥发性可迁移物的非靶向筛查及特征风险标志物的确定

基于超高效液相色谱－四极杆飞行时间质谱（UPLC－Q－TOF MS）对回收聚对苯二甲酸乙二醇酯（回收PET,rPET）全链条中回收碎片及由碎片造粒得到的粒料、瓶坯、瓶子4个阶段rPET样品进行溶解沉淀实验及模拟迁移试验,对样品中的潜在迁移物及迁移物进行非靶向筛查,得到包括PET寡聚体、润滑剂、漂洗剂在内的30种有意、非有意添加物。使用MS－DIAL（Mass spectrometry－data independent analysis software）软件对rPET不同生产阶段的产品标志物进行快速筛选,发现在粒料到瓶坯的加工过程中,生成了新的PET寡聚体;rPET碎片样品中标志物为脂肪醇聚氧乙烯醚,分析可能由漂洗过程引入。对比PET寡聚体的相对含量发现,rPET材料中环状寡聚体的相对含量高于线性寡聚体,其中第二系列环状二聚体的相对含量最高。在rPET加工过程中部分寡聚体及润滑剂的相对含量增加。最后通过TEST（Toxicity estimation software tool）软件预测潜在迁移物及迁移物的大鼠经口急性毒性、发育毒性和致突变性,采用Toxtree软件进行Cramer分级,PET环状寡聚体及酰胺类润滑剂均被分为Cramer Ⅲ级,毒性均高于线性寡聚体,应在rPET加工过程中引起关注。