Application of a novel cyclic ion mobility-mass spectrometer to the analysis of synthetic polymers: A preliminary evaluation

Rationale Mass spectrometry (MS) is often employed in the characterisation of synthetic polymers. As polymer architecture becomes more complex, ion mobility (IM) is increasingly being coupled with MS to provide an additional dimension of separation, along with structural information. In this study, we explore the use of a novel cyclic ion mobility (cIM) mass spectrometer for the analysis of a co-polymer sample. Methods A solution of poly(ethylene glycol)-poly(propylene glycol) random co-polymer (PEG-ran-PPG) was used as a representative polymer sample. The solution was infused into a cIM-enabled quadrupole time-of-flight mass spectrometer. An m/z region of interest, selected using the quadrupole, was passed around the cIM device multiple times. Subsequently, regions of an arrival time distribution were 'sliced' and subjected to tandem mass spectrometric (MS/MS) analysis. Results Typical, multiply charged series were observed for the polymer under electrospray ionisation. Multiple passes of the cIM device resulted in the separation of otherwise-overlapping charge states within a narrow m/z window (similar to 3 m/z units), allowing individual selection of ions. These isolated ions were then subjected to post-mobility fragmentation resulting in clean, high-resolution product ion spectra, with a significant reduction in interference. Conclusions Scalable IM separation (IMS), brought about by passing ions multiple times around the cIM device, was demonstrated to provide increased IM resolution for ions in the selected m/z window. After multiple passes, deconvoluted high-resolution MS/MS product ion spectra were successfully acquired for ions that previously had interfering overlapping species present.