Monkley Charlie, Reay Michaela K, Evershed Richard P, Lloyd Charlotte E M
Organic Geochemistry Unit, School of Chemistry, University of Bristol, Bristol, UK.
School of Geographical Sciences, University of Bristol, Bristol, UK.
Rapid Commun Mass Spectrom. 2024 May 30;38(10):e9726. doi: 10.1002/rcm.9726.
Plastic 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.
Solvent 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.
Unknown 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.
Systematic 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.
塑料地膜可控制种植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（NIASs）。由于这些成分可能会增加农业食品系统中的人为化学负担，其未知的化学性质和行为需要进行研究。
使用电子电离气相色谱 - 质谱联用仪（GC - MS）对一种商用15%聚乳酸（PLA）/85%聚己二酸丁二醇酯 - 对苯二甲酸丁二醇酯共聚物地膜的溶剂提取物进行研究，以表征添加剂和NIAS成分。一些NIASs的模糊性意味着通过常规质谱库比较难以轻易实现其鉴定。因此，几种聚合物衍生化合物的鉴定需要对质谱数据进行解释，并参考更广泛的文献重新应用衍生的裂解模式。使用市售化合物对未知物进行确认。
未知的NIASs被鉴定为聚合物体系单体结构单元组成的环状低聚酯。由聚己二酸丁二醇酯（PBA）和聚对苯二甲酸丁二醇酯（PBT）单体衍生的环状结构通过涉及酯键处1,5 - 和1,3 - H转移的主要途径裂解。在未知物的质谱图中，PBA衍生的环状低聚酯的特征离子为m/z 111、129、183和201，PBT衍生的环状低聚酯的特征离子为m/z 104、132、149和221。还鉴定出含有癸二酸酯部分的环状低聚酯，表明聚丁二酸丁二醇酯作为地膜的意外成分存在。
本文报道的此类系统分析对于提供识别与塑料相关化学品的替代方法具有重要价值。需要公开质谱数据以更深入了解地膜化学成分对引入农业生态系统的环境化学负荷的贡献。
