Nano-electrospray ionization of the negative ions caused by adding esters, aldehydes and ketones in a mobile phase flow

Radić, Martina (2016) Nano-electrospray ionization of the negative ions caused by adding esters, aldehydes and ketones in a mobile phase flow. Diploma thesis, Faculty of Science > Department of Chemistry.

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Abstract

For a wide variety of biological compounds (peptides, proteins, DNA, RNA, carbohydrates),negative ion formation by electrospray ionization is energetically less favorable than positive ion formation in mass spectrometer ion source. One of the reasons is inability to maintain stable electrospray in negative ion mode. Formation and analysis of negative ions of peptides and proteins is of great importance in proteomics research, as they would significantly improve amino acid sequence analysis of proteins and analysis of their posttranslational modifications. Previous research showed favorable effects of formaldehyde on the negative-ion formation of selective androgen receptor modulators. It is assumed that other aldehydes, ketones and esters would have similar effect because their reaction mechanism in acidic medium is similar to the reaction mechanism of formaldehyde. Hybrid T-wave quadrupole time-of-flight mass spectrometer (T-wave Q-TOF MS) was used for the study of nano electrospray formation of negative ions of peptides and proteins. Preselection of the negative-ion enhancers (aldehydes, ketones and esters) showed that the greatest effect on negative-ion formation had 2,2-dimethylpropanal, ethyl methanoate and 2-oxo-2-phenylethanal. The selected negative-ion enhancers were added postcolumn at a flow rate of 0,4 μL min-1 to a mobile phase flow to enhance ionization. Results showed that formation of negativeions of peptides and proteins in ESI-MS was achieved by addition of micromolar quantities of the mentioned negative-ion enhancers to the mobile phase flow.

Item Type: Thesis (Diploma thesis)
Keywords: electrospray ionisation, formaldehyde, mass spectrometry, negative-ion enhancers, negative mode
Supervisor: Cindrić, Mario and Gruić Sovulj, Ita
Date: 2016
Number of Pages: 73
Subjects: NATURAL SCIENCES > Chemistry
Divisions: Faculty of Science > Department of Chemistry
Depositing User: Branka Maravic
Date Deposited: 10 Mar 2016 13:49
Last Modified: 10 Mar 2016 13:49
URI: http://digre.pmf.unizg.hr/id/eprint/4582

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