Characterization of bio-organic and inorganic chemistries using Laser-based Mass Spectrometry

This thesis contributes to the field of in-situ analytical chemistry by further expanding the measurement capabilities of a miniature laser ablation/ionization mass spectrometer (LIMS). The current version of LIMS used in this thesis was developed for in-situ space applications and represents the space-ready prototype of original size and figures of merit. The thesis expands on analytical problems related to the accurate measurement, classification, and identification of mass spectra registered from early (primitive) life and various minerals of inorganic origin. The investigated subjects cover specific aspects of ion generation in time-of-flight mass spectrometry, signal processing, and machine learning, applied to the large mass spectrometric data. The thesis outlines effective solutions for unsupervised characterization of compounds using graph theory and relational data analysis. The current state of space exploration places the identification of signatures of life on Mars among the biggest challenges of our time and represents the frontier of science. The challenge of unambiguous and deterministic identification of biogenicity of the given sample (of unknown origin) is an outstanding problem that requires identification of the range of biological signatures (biosignatures) on the micrometer scale and demands the presence of unique patterns and characteristics that as a whole indicate biological processing. This thesis explores the quality of chemical information that could be gathered from Precambrian microscopic fossils (microfossils) using three different wavelengths of the femtosecond laser radiation used as an ion source in the current LIMS system. The thesis discusses various aspects of mass spectrometric imaging and classification of spectra using the graph-theoretic approaches. Furthermore, the implementation of spectral similarity (proximity) networks will showcase the potential for the deterministic identification of bio-organic and inorganic chemistries. The current results provided in this thesis show high utility and perhaps, yet uncovered potential and importance of LIMS as an analytical method that can be used in future space exploration programs