On 22. August 2019 at 13.15 Jaanus Liigand will defend his doctoral thesis ”Standard substance free quantification for LC/ESI/MS analysis based on the predicted ionization efficiencies”.
senior Research Fellow, Anneli Kruve-Viil, UT
professor Jonathan Martin, University of Stockholmi, Sweden
Liquid chromatography electrospray ionization mass spectrometry (LC/ESI/MS) is a widely applied analytical technique. Furthermore, it is more and more applied in non-target analysis enabling to obtain a more complete picture of biological and chemical processes occurring in living organisms and environment. Standard substances are needed to obtain quantitative information from LC/ESI/MS analysis.
The ultimate aim of my doctoral thesis is to provide a solution to overcome the need of standard substances and to quantify compounds detected and identified with LC/ESI/MS. I propose an approach of estimating the concentration of detected and identified compounds in LC/ESI/MS analysis using predicted electrospray ionization efficiencies and using the ionization efficiency to convert LC/ESI/MS signals to the concentrations of compounds.
To achieve this, I studied the influence of compound structure to ionization efficiency on a large set of compounds. Furthermore, I studied the effect of chromatographic eluent to ionization efficiency covering most widely used organic modifiers, additives and pH. Thirdly, the effect of instrumentation on ionization efficiency was studied and finally the model was developed. Moreover, I developed an approach named shortly Quantem to provide standard substance free quantification in LC/ESI/MS analysis that accounts for specific sample (analytes and matrix) and specific method (eluents used, gradient program and instrumentation). The developed Quantem approach is made available as a software to LC/ESI/MS community.