Tandem mass spectrometric analysis of isosorbide-1,4-cyclohexane-dicarboxylic acid polyester oligomer cations using ion-trap mass spectrometry

Abstract

RATIONALE: Isosorbide is a promising biomass-derived molecule that can be used as a replacement for fossil resource-derived diol monomers used in polyester synthesis. Due to its increased use in sustainable development, it is useful to understand the tandem mass spectrometric (MS/MS) fragmentation pathways of the isosorbide-based copolymer as an aid to interpreting the MS/MS spectra of other isosorbide-containing copolymers. METHODS: Collision-activated dissociation (CAD) experiments were performed on the sodiated/protonated molecules, [(AB)(n)A+Na(or H)](+), n=2-5, of isosorbide (A)-1,4-cyclohexanedicarboxylic acid (B) oligomers formed by ion-trap electrospray ionization (ESI). RESULTS: Product ions arose from cleavage of the bonds between isosorbide and 1,4-cyclohexanedicarboxylic acid. In the MS/MS spectra, f(n)'' product ions were most abundant, followed by e(n) ions. McLafferty rearrangement appeared to provide the most facile pathway to yield the abundant f(n)'' and e(n) ions. In addition, a(n), b(n)'', f(n)''u(n)'', and e(n)(+) ions were observed. Inductive cleavage and -elimination were suggested to be the pathways involved in generating e(n)(+)- and e(n)/b(n)''-type ions, respectively. CONCLUSIONS: Based on the obtained CAD spectra, the alternating sequences of two copolymer building blocks, A and B, were unambiguously determined. The fragmentation pathways leading to the observed product ion types were also established. Copyright (c) 2013 John Wiley & Sons, Ltd.