Liénard Romain, Duez Quentin, Grayson Scott M, Gerbaux Pascal, Coulembier Olivier, De Winter Julien
Interdisciplinary Center for Mass Spectrometry, Organic Synthesis and Mass Spectrometry Laboratory, University of Mons-UMONS, Mons, Belgium.
Center of Innovation and Research in Materials and Polymers, Laboratory of Polymeric and Composite Materials, University of Mons-UMONS, Belgium.
Rapid Commun Mass Spectrom. 2020 Aug;34 Suppl 2:e8660. doi: 10.1002/rcm.8660. Epub 2020 Feb 8.
Since their discovery, cyclic polymers have attracted great interest because of their unique properties. Today, the preparation of these macrocyclic structures still remains a challenge for polymer chemists, and most of the preparation pathways lead to an inescapable contamination by linear by-products. As the properties of the polymers are closely related to their structure, it is of prime importance to be able to assess the architectural purity of a sample.
In this work, the suitability of ion mobility spectrometry-mass spectrometry (IMS-MS) for the quantification of two isomers was investigated. A cyclic poly(L-lactide) was prepared through photodimerization of its linear homologue. Since IMS-MS can be used to differentiate cyclic polymer ions from their linear analogues because of their more compact three-dimensional conformation, the present work envisaged the use of IMS-MS for the quantification of residual linear polymers within the cyclic polymer sample.
Using the standard addition method to plot calibration curves, the fraction of linear contaminants in the sample was determined. By doing so, unrealistically high values of contamination were measured.
These results were explained by an ionization efficiency issue. This work underlines some intrinsic limitations when using IMS-MS in the context of the relative quantification of isomers having different ionization efficiencies. Nevertheless, the linear-to-cyclic ratio can be roughly estimated by this method.
自环状聚合物被发现以来，因其独特的性质而备受关注。如今，这些大环结构的制备对聚合物化学家来说仍是一项挑战，并且大多数制备途径都会不可避免地产生线性副产物污染。由于聚合物的性质与其结构密切相关，能够评估样品的结构纯度至关重要。
在这项工作中，研究了离子淌度质谱联用技术（IMS-MS）对两种异构体进行定量分析的适用性。通过其线性同系物的光二聚反应制备了环状聚（L-丙交酯）。由于 IMS-MS 可利用环状聚合物离子更紧凑的三维构象将其与线性类似物区分开来，因此本研究设想使用 IMS-MS 对环状聚合物样品中的残留线性聚合物进行定量分析。
采用标准加入法绘制校准曲线，测定了样品中线性污染物的比例。结果发现，所测得的污染值高得离谱。
这些结果是由电离效率问题导致的。这项工作强调了在对具有不同电离效率的异构体进行相对定量分析时使用 IMS-MS 存在的一些固有局限性。然而，通过这种方法可以大致估算线性与环状的比例。
