Ubeda Sara, Aznar Margarita, Nerín Cristina
Department of Analytical Chemistry, EINA, University of Zaragoza, Campus Rio Ebro, María de Luna 3, 50018, Zaragoza, Spain.
Anal Bioanal Chem. 2018 Mar;410(9):2377-2384. doi: 10.1007/s00216-018-0902-4. Epub 2018 Feb 10.
An oligomer is a molecule that consists of a few monomer units. It can be formed during polymer manufacturing and also due to polymer degradation processes or even during use conditions. Since oligomers are not included in chemical databases, their identification is a complex process. In this work, the oligomers present in 20 different PET pellet samples have been determined. Two different sample treatment procedures, solvent extraction and total dissolution, were applied in order to select the most efficient one. The analyses were carried out by UPLC-MS-QTOF. The use of high resolution mass spectrometry allowed the structural elucidation of these compounds and their correct identification. The main oligomers identified were cyclic as well as lineal from the first, second, and third series. All of them were composed of terephthalic acid (TPA), diethylene glycol (DEG), and ethylene glycol (EG). Quantitative values were very different in both procedures. In total dissolution of PET samples, the concentration of oligomers was always, at least, 10 times higher than in solvent extraction; some of the compounds were only detected when total dissolution was used. Results showed that the oligomers with the highest concentration values were dimers and trimers, cyclic, as well as lineal, from the first and second series. The oligomer with the maximum concentration value was TPA-EG-DEG that was found in all the samples in a concentration range from 2493 to 19,290 ng/g PET. No differences between virgin and recycled PET were found. Migration experiments were performed in two PET bottles, and results showed the transference of most of these oligomers to a fat food simulant (ethanol 95%). Graphical abstract Graphical abstract of the two procedures developd and optimized for identifying oligomers in PET pellets and in migration form PET bottles.
低聚物是一种由少数单体单元组成的分子。它可在聚合物制造过程中形成，也可归因于聚合物降解过程，甚至在使用条件下形成。由于低聚物未包含在化学数据库中，其鉴定是一个复杂的过程。在本研究中，已测定了20个不同PET颗粒样品中存在的低聚物。应用了两种不同的样品处理程序，即溶剂萃取和完全溶解，以选择最有效的一种。分析通过超高效液相色谱-质谱-四极杆飞行时间质谱仪（UPLC-MS-QTOF）进行。高分辨率质谱的使用使得这些化合物的结构得以阐明并得到正确鉴定。鉴定出的主要低聚物有来自第一、第二和第三系列的环状以及线性低聚物。它们均由对苯二甲酸（TPA）、二甘醇（DEG）和乙二醇（EG）组成。两种程序中的定量值差异很大。在PET样品的完全溶解中，低聚物的浓度总是比溶剂萃取中至少高10倍；有些化合物仅在使用完全溶解时才能检测到。结果表明，浓度值最高的低聚物是来自第一和第二系列的环状以及线性二聚体和三聚体。浓度值最高的低聚物是TPA-EG-DEG，在所有样品中的浓度范围为2493至19290 ng/g PET。未发现原生PET和回收PET之间存在差异。在两个PET瓶中进行了迁移实验，结果表明这些低聚物中的大多数转移到了一种高脂肪食品模拟物（95%乙醇）中。图形摘要 为鉴定PET颗粒中的低聚物以及PET瓶迁移中的低聚物而开发和优化的两种程序的图形摘要。
