Tools for applied soft ionization mass spectrometry
Time: Tue 2021-06-08 10.00
Subject area: Chemistry
Doctoral student: Joakim Romson , Tillämpad fysikalisk kemi
Opponent: Professor Steven Wilson, University of Oslo
Supervisor: Åsa Emmer, Kemi, Tillämpad fysikalisk kemi; Peter Dinér, Organisk kemi
Mass spectrometry (MS) is an important analytical tool. Its most importantadvantages are sensitivity, resolution, and accurate and precise m/zmeasurements. To get the best results from an instrument, the user musthave knowledge of its limitation and requirements.The sensitivity of matrix assisted laser desorption/ionization (MALDI)-MSis dependent on the surface concentration of the sample. In Paper I, ahighly hydrophobic surface coating was developed and applied to MALDItarget plates. This allowed applied sample droplets to dry down ontosmaller areas. Compared to untreated and commercial concentrationplates, the surface treated plates gave on average twice the signal to noisefor peptide analysis.Signal suppression and signal overlap in MS can obscure analyte signals.In Paper II, an automated system for coupling capillary electrophoresis toMALDI-MS was developed. Separation of butterfly spermatophoreproteins into 32 fractions revealed some otherwise not detected oroverlapping MS signals.Calibration is vital for accurate MS measurements. In Paper III, adendrimer-based calibration solution for electrospray ionization (ESI)-MSwas developed, intended for peptide analysis. With a larger number ofsignals in the m/z range of interest, precision, and probably accuracy,improved compared to a commercial calibration solution.In Paper IV, calibration options for ESI-MS were reviewed. Factorsaffecting accuracy and precision, in general and for different instruments,were summarized, and a comprehensive list of calibrants was compiled.Paper V further investigated accuracy and precision in MS, specificallyregarding chemical mass shifts in ion traps. It was shown that clusters andsome adduct ions would be unsuitable for calibration of ion traps, and thatlinear ion traps showed mass shifts similar to spherical ion traps.