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Nitsche T, Sheil MM, Blinco JP, Barner-Kowollik C, Blanksby SJ. Electrospray Ionization-Mass Spectrometry of Synthetic Polymers Functionalized with Carboxylic Acid End-Groups. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:2123-2134. [PMID: 34242006 DOI: 10.1021/jasms.1c00085] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Electrospray ionization-mass spectrometry (ESI-MS) of low-charging synthetic polymers typically produces mass spectra exhibiting a bias toward the low-mass region of the polymer mass distribution. To examine the origin(s) of this ionization bias, narrow dispersity polystyrene polymers (Đ < 1.10) were prepared with ionizable carboxylic acid end-groups at one or both chain termini. The mixture complexity was further reduced through preparative size-exclusion chromatography (SEC), and these well-defined polymers were subjected to negative ion ESI-MS on a high-resolution instrument with a mass-to-charge (m/z) range up to 8000. Incorporation of one carboxylic acid end-group facilitated the generation of singly charged [M - H]- ions across the entire range of the mass analyzer. The comparison of mass spectra with size-exclusion chromatograms of the same polymer revealed an ionization bias toward lower masses, which was partially overcome through fractionation, modification of electrospray solvent, and increased declustering potentials. Incorporation of a second ionizable moiety within polymers of equivalent size facilitated multiply charged [M - 2H]2- ion formation with significantly improved ionization efficiency, spectral coverage of the molar mass distribution, and minimal cluster ion formation. These findings indicate that increased charging of polymers through multiple, well-defined sites of ionization can enhance volatilization and ionization of higher-mass polymers. Generation of higher-molecular-weight polymers in low-charge states-while possible under ideal conditions-competes ineffectively with either nonspecific, multiple-charging of similar sized polymers or ionization of the smaller polymers in the distribution.
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Affiliation(s)
- Tobias Nitsche
- School of Chemistry and Physics, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
- Centre for Materials Science, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
| | - Margaret M Sheil
- School of Chemistry and Physics, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
| | - James P Blinco
- School of Chemistry and Physics, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
- Centre for Materials Science, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
| | - Christopher Barner-Kowollik
- School of Chemistry and Physics, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
- Centre for Materials Science, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
| | - Stephen J Blanksby
- Centre for Materials Science, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
- Central Analytical Research Facility, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
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Wang H, Leeming MG, Ho J, Donald WA. Origin and Prediction of Highly Specific Bond Cleavage Sites in the Thermal Activation of Intact Protein Ions. Chemistry 2018; 25:823-834. [DOI: 10.1002/chem.201804668] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Indexed: 11/09/2022]
Affiliation(s)
- Huixin Wang
- School of Chemistry University of New South Wales Sydney New South Wales Australia
| | - Michael G. Leeming
- School of Chemistry, Bio21 Institute of Molecular Science and Biotechnology The University of Melbourne Melbourne Victoria Australia
| | - Junming Ho
- School of Chemistry University of New South Wales Sydney New South Wales Australia
| | - William A. Donald
- School of Chemistry University of New South Wales Sydney New South Wales Australia
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