Interfacing Multistage Mass Spectrometry with Liquid Chromatography or Ion Mobility Separation for Synthetic Polymer Analysis

Abstract

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.

Ion mobility spectrometry – Mass spectrometry coupling for synthetic polymers

“…Although the measured drift times could not be converted into TW CCS N2 values due to the lack of appropriate anionic calibration standards in the targeted working range, molecular modeling results allowed these two structures to be assigned. A more compact conformation is found for the macrocyclic structure (e.g., 196 Å 2 for n = 7) than for the tadpole‐shape architecture (e.g., 218 Å 2 for n = 7) consisting of one linear chain branched to a small cyclic head …”

“…IMS‐MS coupling was also used in the negative ion mode to identify the architecture of oligo(chlorophosphazene) isomers . These inorganic species contain an alternating phosphorus–nitrogen bond sequence and each P atom holds two chlorine substituents.…”

Mehrdimensionale Massenspektrometrie von synthetischen Polymeren und modernen Materialien

“…Schließlich können bei der ESI Überlagerungen von Ladungsverteilungen auftreten, wodurch Massebestimmung und Bestimmung der Zusammensetzung erschwert werden. Wie hier gezeigt werden wird, können derartige Probleme durch Anwendung der Tandem‐Massenspektrometrie (d. h. von zweidimensionaler Massenspektrometrie, MS/MS) und/oder durch Kopplung der MS mit einer orthogonalen Trennung – entweder Flüssigkeitschromatographie (LC) vor der Ionisation oder Ionenmobilitätsmassenspektrometrie (IM‐MS) nach der Ionisation – überwunden werden . Durch Verknüpfen dieser Methode mit der thermischen Zersetzung wird ihre Anwendbarkeit auf große, vernetzte Polymere erweitert, die nicht direkt ionisiert werden können …”

“…Für die Online‐LC‐MS kann eine Methode der Ionisation unter Umgebungsbedingungen, wie ESI oder APCI, genutzt werden . LC‐Arten, die mit der MS‐Detektion zur Analyse synthetischer Polymere gekoppelt wurden, sind die Größenausschlusschromatographie (SEC), die Flüssigkeitschromatographie unter kritischen Bedingungen (LCCC) und die Interaktionsflüssigkeitschromatographie, auch bekannt als Adsorptionsflüssigkeitschromatographie (LAC) .…”

Multidimensional mass spectrometry to characterize degradation products generated during MALDI of polystyrenes prepared by controlled radical polymerization techniques

“…Such an analytical set-up was previously reported to efficiently resolve isotope cluster overlaps of polymer ions in studies involving electrospray as the ionization source. [31][32][33][34] All MS/MS data were then analyzed based on the fragmentation rules reported for linear PS. 30 Briefly, dissociation reactions were described to occur according to radical mechanisms followed by various rearrangements, leading to product ions containing either one or the other end-group (as depicted in the Supporting Information Scheme S2) and detected in the low m/z range of MS/MS spectra.…”