Department of Analytical Chemistry, EINA, University of Zaragoza, Campus Rio Ebro, María de Luna 3, 50018, Zaragoza, Spain.
Anal Bioanal Chem. 2019 Jun;411(16):3521-3532. doi: 10.1007/s00216-019-01831-0. Epub 2019 May 4.
Polylactic acid (PLA) is a biopolymer commonly used in food packaging due to its good characteristics, similar to PET. To evaluate the safety of this material, the analysis of the non-intentionally added substances (NIAS) is required. Oligomers are NIAS and their behavior needs a deep study, especially if they migrate to the food. In this work, the analysis of the polymer and the migration to food simulants was carried out. A total dissolution/precipitation procedure was applied to PLA pellets and films, using dichloromethane and ethanol as solvent and antisolvent system respectively. The migration tests were carried out in three liquid simulants to mimic any kind of food. Since oligomers are not present in the positive list of the Directive 10/2011/EC, their concentration must be below the 0.01 mg/kg of food. UPLC-QTOF-MS, with and without ion mobility (IM), was used for the analysis. Thirty-nine different PLA oligomers made of repeated monomer units of [LA] (CHO) and with different structures were identified. They corresponded to cyclic oligomers with [LA] structure and two groups of linear oligomers, one with an hydroxyl group, OH-[LA]-H, and the other one with an ethoxy group, CH-CH-O-[LA]-H. Cyclic oligomers only appeared in the material and were not present in migration solutions. Linear oligomers HO-[LA]-H were already present in the pellets/film and they migrated in a higher extension to aqueous food simulants (EtOH 10% and AcH 3%). However, linear oligomers CH-CH-O-[LA]-H were not present initially in the pellets/film, but were detected in migration to simulants with ethanol content, EtOH 95% and EtOH 10%. Furthermore, 5 cyclic polyester oligomers were identified in migration. Ethanol 95% and ethanol 10% migration solutions were also analyzed by scanning electron microscopy (SEM), and the presence of microstructures that could be attributed to the oligomers migration was found. They could be seen as microplastics.
聚乳酸（PLA）是一种常用于食品包装的生物聚合物，因其具有类似于 PET 的良好特性而被广泛使用。为了评估这种材料的安全性，需要对非故意添加物质（NIAS）进行分析。低聚物是 NIAS，它们的行为需要深入研究，特别是如果它们迁移到食品中。在这项工作中，对聚合物进行了分析，并对其向食品模拟物的迁移进行了研究。采用完全溶解/沉淀程序对 PLA 颗粒和薄膜进行处理，分别使用二氯甲烷和乙醇作为溶剂和反溶剂体系。迁移测试在三种液体模拟物中进行，以模拟任何种类的食品。由于低聚物未列在指令 10/2011/EC 的正面清单中，因此其浓度必须低于食品 0.01mg/kg。使用带有和不带有离子淌度（IM）的超高效液相色谱-四极杆飞行时间质谱（UPLC-QTOF-MS）进行分析。鉴定出 39 种不同的 PLA 低聚物，它们由 [LA]（CHO）的重复单体单元组成，具有不同的结构。它们对应于 [LA] 结构的环状低聚物和两组线性低聚物，一组具有羟基，OH-[LA]-H，另一组具有乙氧基，CH-CH-O-[LA]-H。环状低聚物仅出现在材料中，不存在于迁移溶液中。HO-[LA]-H 线性低聚物已经存在于颗粒/薄膜中，并在更高程度上迁移到水性食品模拟物（EtOH 10%和 AcH 3%）中。然而，CH-CH-O-[LA]-H 线性低聚物最初不存在于颗粒/薄膜中，但在迁移到含有乙醇的模拟物中时被检测到，如 EtOH 95%和 EtOH 10%。此外，在迁移中还鉴定出 5 种环状聚酯低聚物。还对乙醇 95%和乙醇 10%的迁移溶液进行了扫描电子显微镜（SEM）分析，发现存在可能归因于低聚物迁移的微观结构。它们可以被视为微塑料。
