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

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.