RationalePlastic mulch film manages weed growth and moisture loss on the surface of cropping beds. The chemical components of such plastics include polymer(s), additives and non‐intentionally added substances (NIASs). The unknown chemical nature and behaviours of these constituents require investigation due to their potential to add to the anthropogenic chemical burden in the agrifood system.MethodsSolvent extracts of a commercial 15% polylactic acid (PLA)/85% poly(butylene adipate‐co‐terephthalate) mulch film were investigated using gas chromatography–mass spectrometry (GC–MS) with electron ionisation to characterise the additive and NIAS components. The obscurity of some of the NIASs meant their identification was not readily achieved through routine MS library comparisons. As such, the identification of several polymer‐derived compounds required interpretation of the MS data and re‐application of the derived fragmentation patterns with reference to the wider literature. Unknowns were confirmed using commercially available compounds.ResultsUnknown NIASs were identified as cyclic oligoesters comprised of the monomeric building blocks of the polymer system. Cyclic structures derived from the monomers of polybutylene adipate (PBA) and polybutylene terephthalate (PBT) fragmented through a primary pathway involving 1,5‐ and 1,3‐H transfers at ester linkages. Characteristic ions at m/z 111, 129, 183 and 201 for PBA‐derived cyclic oligoesters and m/z 104, 132, 149 and 221 for PBT‐derived cyclic oligoesters were assigned in the mass spectra of unknowns. Cyclic oligoesters containing sebacate moieties were also identified, indicating the presence of polybutylene sebacate as an unexpected component of the mulch.ConclusionsSystematic analyses of the sort reported here are valuable for providing alternative approaches for the identification of plastic‐related chemicals. Open publication of MS spectral data is required to build a greater understanding of the mulch film chemical components contributing to the environmental chemical load introduced to agroecosystems.

中文翻译：

---

可生物降解地膜中环状低聚酯的质谱表征

基本原理塑料地膜可以控制耕作床表面的杂草生长和水分流失。此类塑料的化学成分包括聚合物、添加剂和非有意添加物质 (NIAS)。这些成分的化学性质和行为未知，因为它们有可能增加农业食品系统中的人为化学负担，因此需要进行调查。方法商业 15% 聚乳酸 (PLA)/85% 聚己二酸丁二醇酯的溶剂提取物共使用气相色谱-质谱法 (GC-MS) 和电子电离技术对地膜进行了研究，以表征添加剂和 NIAS 成分。一些 NIAS 的模糊性意味着通过常规 MS 文库比较很难轻松实现对它们的识别。因此，鉴定几种聚合物衍生的化合物需要解释 MS 数据，并参考更广泛的文献重新应用衍生的碎片模式。使用市售化合物确认了未知物。结果未知的 NIAS 被鉴定为由聚合物系统的单体结构单元组成的环状低聚酯。衍生自聚己二酸丁二醇酯 (PBA) 和聚对苯二甲酸丁二醇酯 (PBT) 单体的环状结构通过涉及酯键上 1,5- 和 1,3-H 转移的主要途径断裂。特征离子质量分数111、129、183 和 201 用于 PBA 衍生的环状低聚酯和质量分数未知物的质谱中指定了 PBT 衍生的环状低聚酯的 104、132、149 和 221。还鉴定出含有癸二酸酯部分的环状低聚酯，这表明聚癸二酸丁二醇酯作为覆盖物的意外成分存在。结论本文报告的系统分析对于提供识别塑料相关化学品的替代方法很有价值。为了更好地了解影响农业生态系统环境化学负荷的地膜化学成分，需要公开发布质谱数据。