On 18 August at 12:15 Artur Gornischeff will defend his thesis “Study of ionization efficiencies for derivatized compounds in LC/ESI/MS and their application for targeted analysis” for obtaining the degree of Doctor of Philosophy (Chemistry).
Riin Rebane (PhD), UT Institute of Chemistry
Prof. Tuulia Hyötyläinen, University of Örebro Ülikool, Sweden
Liquid chromatography electrospray ionization (tandem) mass spectrometry LC/ESI/MS(MS) is the most versatile and powerful analytical method for analyzing hundreds of analytes from various different matrices in very low quantities. Until today, majority of studies, methods and application still use standard substances to quantitatively determine analytes in question. The aim of this doctoral thesis was to provide solution to eliminate standard substances for targeted analysis of derivatized compound for analysis carried out with LC/ESI/MS/MS.
First, the method of logIE measurement for derivatized amino acids was developed it was studied how derivatization changes ionization efficiency (IE) in the ESI source. Results showed that in most cases, derivatization enhances IE. In addition, logIE values obtained in this work were also linked to previously measured logIE scales in order to further broaden these scales.
During the method development and application of the new logIE measurement system using the chromatographic column, it was compared how different ionization sources and eluents would correlate with each other in respect of logIE. In case of ESI source, a high correlation (R2=0.71 and 0.79) was observed and in this case, logIE values measured in flow-injection mode would be highly beneficial to assess sensitivity for chromatographic method with either solvent.
Since most practical applications nowadays use MS/MS analysis, the next aim was to evaluate the correlation of measured logIE values with response factors (logRF) in MS/MS and apply these values to estimate analyte concentration without standard substances in different matrices. This method showed good correlation between logIE and logRF values, which were both used for estimating amino acid concentration in beer, wine and tea. Both estimates (logIE and logRF) showed very high correlation compared to concentrations obtained with a calibration curve method. Therefore, it was concluded that this approach would be useful tool to make a targeted scan very effective for many analytes together to evaluate their concentration, by which it is possible to distinguish counterfeit drinks from the original ones.
As demonstrated, standard free quantitation for targeted MS/MS analysis is possible. It will open lots of possibilities for a wide area of different application to perform such analysis. This application could possibly be expanded to other reagents and analytes which in turn widens even more range of use such approach.
Link of defense: Microsoft Teams