Novel clean-up, concentration and laser desorption/ionization strategies for mass spectrometry

Abstract: Despite valuable advantages of mass spectrometry (MS) techniques they still have drawbacks that need to be overcome, notably their sensitivity to various kinds of interfering substances and associated difficulties involved in detecting signals from analytes present in trace quantities. Thus, high quality analytical data could be acquired by improving sample pre-treatment techniques and/or ionization methods to increase ionization yields and/or avoid the generation of unwanted ions.In the studies this thesis is based upon, a microfluidic electrocapture system capable of trapping charged proteins/polypeptides while non-charged species such as non-ionic detergents are swept out, was used to decrease the concentration of detergent in samples containing soluble and membrane associated proteins/polypeptide. Subsequent mass spectrometric analysis yielded well-resolved mass spectra of the target analytes.In addition, it was found that solid phase extraction (SPE) sorbents such as graphitized carbon black (GCB), can efficiently assist the laser desorption ionization of small molecules without generating any interfering ions which inspired the fabrication of ?-traps and discs. Other matrix-free approaches demonstrated the utility of silicon nitride and oxidized GCB nanoparticles as versatile media for surface-assisted laser desorption ionization (SALDI) of small molecules.In this thesis it is discussed that small molecule analytes such as Polyphenols present in red wine and quaternary protoberberine alkaloids with highly conjugated systems and acidic/permanently charged functional groups can be readily analyzed without any matrix or assisting-surface.In summary, the microfluidic electrocapture, new laser desorption ionization methods and surfaces, as well as integrated SALDI and SPE platforms, introduced in this work extend the MS strategies allowing coverage of a wider range of samples.