Ionization Competitors Extend The Linear Range Of Electrospray Ionization Mass Spectrometry
Bazzi, Bilal H.
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ESI-MS has proven its applicability in quantitative analysis for a wide range of analytes. Its effectiveness relies on achieving sensitivity and linear range, although the latter is known to be limited. ESI-MS response varies among charged species due to differences in analyte structure. The working curve associated with quantitative analysis has a limit of linearity. At high analyte concentration, instrument response plateaus because the surface of the charged droplet reaches saturation. Several studies have proposed to enhance the linear range by enhancing gas-phase analyte charging, by facilitating droplet evaporation, or by improving ion transmission through the mass spectrometer. This thesis focuses on examining the usefulness of surface–active ionization competitor co-analytes to extend the upper LR range of ESI–MS. The introduction of ionization competitors, such as tetraalkyl ammonium acetates and poly glycols allow for an enhancement in the working curve associated with quantitative analysis at higher analyte concentrations, through an increase in the linear range with minimal sacrifice in sensitivity. Discrete measurements reveal an increase in LOL from ≤100 μM (without competitor) to ~350 μM (with competitor).