On 15. August 2019 Piia Liigand will defend her doctoral thesis „Expanding and improving methodology and applications of ionization efficiency measurements“).
senior research fellow, Anneli Kruve-Viil, UT
research fellow Karl Kaupmees , UT
professor Susan Richardson, University of South Carolina, USA
Electrospray ionization (ESI) is a method used to produce gas phase ions in which high voltage is applied to a liquid. ESI is commonly used to couple liquid chromatography (LC) and mass spectrometry (MS). LC/ESI/MS enables to determine trace amounts of organic compounds and is thus an important tool in various fields, e.g. environmental analysis, drug discovery, metabolomics, proteomics, and food safety.
Compounds have several orders of magnitude different ionization efficiencies in ESI source leading to a misestimation of concentrations up to million times if just signals are used for quantification. Ionization efficiency prediction possesses high potential to overcome the lack of standard substances in LC/ESI/MS analysis. The aim of this thesis was to broaden the existing understanding of ESI in terms of analytes, matrices, instrument and developing a strategy to unify the vastly different and contradictory ionization efficiency measurements into one dataset. All of the gained knowledge throughout this work will allow the development of a universal model for predicting concentrations which is not limited to specific compound families, matrices or instrumental setups.
The results of this thesis enabled to expand ionization efficiency measurement methodology to multiply charged analytes and allowed for direct quantitative comparison of ionization efficiencies measured in different ESI modes, matrices and even in different labs. The gained knowledge lays a solid foundation to move forward with a universally applicable ionization efficiency prediction model that would allow standard substance free quantification as well as possible deeper understanding of the ESI process.