Mass Analysis of synthetic polymer MALDI ions with a charge detector coupled to linear ion trap mass spectrometer

Thi Khanh Ly Lai^1*, Justin Benedict Agbayani Agcaoili¹, Avinash A. Patil¹, Zhe-Xuan Liu¹, Yi-Pang Chiu¹, Wen-Ping Peng¹

¹Physics, National Dong Hwa Univesity, Hualien, Taiwan

* Presenter:Thi Khanh Ly Lai, email:laithikhanhly@gmail.com

Synthetic polymers constitute the majority of materials nowadays. So far, mass spectrometry has been undertaken to be the most feasible method for determining the composition and properties of synthetic polymers. However, few studies have been conducted with the linear ion trap (LIT) technique for synthetic polymer detection analysis. The LIT mass analyzer is flexible to be combined with other mass analyzers for tandem mass spectrometry (MS/MS). Due to its small size, it is also appropriate for the development of benchtop mass spectrometers. The development of LIT-MS coupled with a charge detector (CD) for the analysis of polystyrene in the mass range of 3,700 to 200,000 Thomson (Th) is presented in this study. For the analysis of polystyrene samples in LIT-MS, it was discovered that optimizing ion ejection methods and buffer gas pressure is critical. The spectral analysis performed by LIT-MS with voltage scan or frequency scan with resonance ejection with low-mass polystyrene 3,700 and 13,000 was comparable to the spectral analysis performed by commercial MALDI-TOF MS. The voltage scan method with resonance ejection was unable to analyze high mass polystyrene samples with masses exceeding 20,000 daltons. Frequency scan with resonance ejection, on the other hand, was discovered to be the most efficient method of scanning high mass polystyrene ions. For mass analysis of polystyrene 50,000 with LIT-MS, dual-stage cooling and buffer gas selection are crucial. The heavier collision gas molecules Ar (argon) introduced in the ionization stage, in comparison to the light buffer gas He (helium), not only assisted in the efficient cooling of higher mass ions but also allowed the LIT to operate at lower pressures (~ 1 mTorr for He and ~ 0.5 mTorr for Ar). Multimers analysis of polystyrene 50,000 was carried out with He buffer gas pressure of 0.53 mTorr in the ionization chamber and 0.64 mTorr of Ar in LIT chamber and mass range of LIT can be extended to pentamer, 250,000 Th. Finally, the mass analysis of singly and doubly charge polystyrene with a mass of 200,000 daltons was accomplished using LIT-MS.

Keywords: Synthetic polymers, Linear ion trap, Polystyrene, Mass spectrometry, Charge detector