Analysis of Small Biomolecules by Esi- and Maldi-Mass Spectrometry

Abstract

This thesis describes the use of mass spectrometric methods based upon electrospray ionization, ESI, and (matrix-assisted) laser desorption/ionization, (MA)LDI, for the quantitative analysis of small biomolecules. Structure analysis when required, was obtained through tandem mass spectrometry (MS/MS). The Girard type reagent, 4-hydrazino-4-oxobutyl tris(2,4,6 trimethoxy)phenyl phosphonium bromide, in combination with the solid phase derivatization technique, is used to selectively prepare a pre-ionized malondialdehyde derivative to be analyzed by MALDI or LDI. The in situ derivatization and isolation minimize interferences from other components in biological samples. The combination of pre-ionization and aromatic functionalities allows for laser induced ionization without the need of matrix. The combination of these techniques provides an avenue for development of automation to produce a high throughput method of analysis. Chapter 3 involves the study of the complexation of diols to the oxovanadium ion. The oxovanadium (IV) complex of ethylene glycol is used as a reference to study the complexation of other diols and amines with the vanadyl ion. The ES spectra of various diols studied produce intense signals for the mixed and the analyte complexes, indicating effective complexation of the analytes with the vanadyl ion. Oxovanadium (IV) is observed to be more selective for complexation to diols than amines. This eliminates the possibility of interference from N-containing ligands to the detection of diols by the reference complex. The electrospray spectrum is used for quantitation and the tandem mass spectrometry spectrum for structure confirmation. The MS/MS spectrum also assists the identification of the diols by the structural differences within their isomers. The equilibrium constant of a set of diols was determined and its calibration curve were constructed. This study produces an alternative method to detect and quantify diols in aqueous solutions and blood samples.