Structural analysis of polymer end groups by electrospray ionization high-energy collision-induced dissociation tandem mass spectrometry

Chemical structures of polymer end groups play an important role in determi ning the functional properties of a polymeric system. We present a mass spe ctrometric method for determining end group structures. Polymeric ions are produced by electrospray ionization (ESI), and they are subject to source f ragmentation in the ESI interface region to produce low-mass fragment ions. A series of source-fragment ions containing various numbers of monomer uni ts are selected for high-energy collision-induced dissociation (CID) in a s ector/time-of-flight tandem mass spectrometer. It is shown that high-energy CID spectra of source;induced fragment ions are very informative for end g roup structure characterization. By comparing the CID spectra of fragment i ons with those of known chemicals, it is possible to unambiguously identify the end group structures. The utility of this technique is illustrated for the analysis of two poly(ethylene glycol)-based slow-releasing drugs where detailed structural characterization is of significance for drug formulati on, quality control, and regulatory approval. Practical issues related to t he application of this method are discussed.