Interfacing multistage mass spectrometry with liquid chromatography or ion mobility separation for synthetic polymer analysis

摘要

Synthetic polymers are naturally mixtures of homologs, even in pure form. More complexity is introduced by the presence of different comonomers, end groups and/or macromolecular architectures. The analysis of such systems is substantially facilitated by interfacing mass spectrometry (MS), which disperses based on mass, with an additional level of separation involving either interactive liquid chromatography (LC) or ion mobility (IM) spectrometry, both of which are readily coupled online with electrospray ionization and MS detection. IM-MS separates in the gas phase, post-ionization and, therefore, is ideally suitable for labile and reactive polymers. Its usefulness is illustrated with the characterization of non-covalent siloxane-saccharide complexes, metallosupramolecular assemblies and an air- and moisture-sensitive inorganic polymer, poly(dichlorophosphazene). Conversely, LC-MS which separates in solution phase, before ionization, is most effective for the analysis of polymeric mixtures whose components differ in polarity. Interactive LC conditions can be optimized to disperse by the content of hydrophobic units, as is demonstrated for amphiphilic polyether copolymers and sugar-based nonionic surfactant blends. Both LC-MS and IM-MS can be extended into a third dimension by tandem mass spectrometry (MS ~2) studies on select oligomers, in order to obtain insight into individual end groups and isomeric architectures, comonomer sequences and degree of substitution, for example, by hydrophobic functionalities.