Sequencing of specific copolymer oligomers by electron-capture-dissociation mass spectrometry.
Although a poly(ethylene/propylene glycol) (PEG/PPG) copolymer mixture is far too complex (approximately 150 oligomeric formulas) for conventional purification, oligomer ion compositions of <1% abundance can be separated by Fourier transform mass spectrometry and dissociated into sequence-specific fragment ions. Using collisionally activated dissociation (CAD) or other conventional energetic methods, we found that misleading rearrangements are common; however, these are negligible with electron capture dissociation (ECD), consistent with its nonergodic mechanism. Despite the lack of reference compounds, ECD of five oligomers ranging from PEG(1)PPG(18) to PEG(9)PPG(15) shows that approximately 80% of their isomers have all PEG units at one end, while CAD gave lower values because of an approximately 21% rearrangement loss of internal monomer units. In contrast to the indicated triblock "PEG/PPG/PEG" sample designation of this commercial surfactant, all of these oligomers are found to consist primarily of diblock PEG/PPG structures, so that their termini differ significantly in hydrophobicity, as expected for a surfactant.
Cerda
Blas A
BA
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA.
Horn
David M
DM
Breuker
Kathrin
K
McLafferty
Fred W
FW
D006018:Glycols / Q000737:chemistry; D007202:Indicators and Reagents; D020442:Poloxamer; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D011409:Propylene Glycols / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013501:Surface-Active Agents
D006018:Glycols; D007202:Indicators and Reagents; D011108:Polymers; D011409:Propylene Glycols; D013501:Surface-Active Agents; D020442:Poloxamer; C012504:polypropylene glycol; D011092:Polyethylene Glycols