Analytical Sciences

Analysis of Multiply Charged Poly(ethylene oxide-co-propylene oxide) Using Electrospray Ionization–Ion Mobility Spectrometry–Mass Spectrometry

Kanako ITO, Shinya KITAGAWA, and Hajime OHTANI

Department of Life Science and Applied Chemistry, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan

Poly(ethylene oxide), poly(propylene oxide), and their copolymer (poly(EO-co-PO)) were analyzed by electrospray ionization–ion mobility spectrometry–mass spectrometry (ESI-IMS-MS). ESI produced multiply charged analytes of 2 to 5 Na⁺ additions, and they were separately observed in a 2D map of m/z value vs. drift time. The collision cross-section of the analyte polymers was almost linearly proportional to (molecular weight)^0.644, except for the analytes with 2Na⁺ addition; a nonlinear relation called “folding” was significantly observed for the analytes with 2Na⁺ addition. An increase in electrostatic repulsion, because of the increase in Na⁺ addition, suppressed the folding of the polymer. Analyses of poly(EO-co-PO) with different EO compositions revealed that the copolymer with high EO composition tended to show folding. The separation of highly multiply charged poly(EO-co-PO)s with different EO contents by ESI-IMS-MS was successfully demonstrated.

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