Fundamentals and applications of charge inversion: Manipulations of ions during ion/ion reactions in the gas-phase for the analysis of biopharmaceutical-relevant molecules

Kerry M Hassell, Purdue University

Abstract

With the ability to isolated, store, trap, and react ions for steps in an ion/ion reaction, hybrid mass spectrometers such as triple quadrupoles (QqQ) provide the highest flexibility and performance for gas-phase ion/ion reaction studies. The ability for QqQ to store ions of the opposite polarity allow ion/ion reactions such as charge inversion to be performed. The first step to all charge inversion experiments presented includes proton transfer from the reagent to the analyte, which reacts through a neutralization intermediate, and finally inverts the polarity of the original analyte ion. Using this charge inversion method unwanted cations can be removed from metabolite ions to concentrate the analyte signal into one ion. In order to improve sequence coverage of peptides, an ion/ion reaction was developed to covalently modify the analyte peptide in the gas-phase. This modified ion was subjected to two stages of ion trap collisional induced dissociation (CID) where fragment ions were observed. The detection of corticosteroids, another type of analyte studied in this thesis, was improved when reacted with a multiply charged reagent dendrimer ion spiked with a metal salt, improved the detection of the steroid. This process is a new type of ion/ion reaction where not only a proton was transferred but an anionic species as well (i.e. Cl−, NO2 −, etc…). A charge state dependent study was performed with multiple reagent ions in order for results to be obtained of charge inversion efficiency based on charge state. This provides more information on the nature of the reagent ion, and demonstrates that intermediate charge states give the highest efficiency. Amino acids in complex biological matrices yield complex mass spectra. By using charge inversion, the signal-to-noise is improved and the lower limits of detection can be reached. Finally, it was found that the electrostatic interaction between the reagents and the analyte ions was so strong that when the complex was subjected to CID the covalent bonds would fragment before the electrostatic bonds.

Degree

Ph.D.

Advisors

McLuckey, Purdue University.

Subject Area

Analytical chemistry

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