| Mass spectrometry is a powerful analytical technique used for chemical characterization and can be particularly helpful in confirmatory forensic analysis. Recent research has shown laser desorption/mass spectrometry (LD/MS) effective in the analysis of dyes found in inks on paper. In this thesis, mass spectra obtained from direct UV-laser irradiation of a variety of samples are presented. These samples include currency, postage stamps, fabric, watercolor pigments on paper, black and white photographs, glass, and compounds used in currency protection devices. While other techniques have been used to analyze these samples, LD/MS produces unique data. Both positive-ion and negative-ion mass spectra contain useful and relevant molecular level information about compounds present in the samples. The interpretation of LD/MS mass spectra and the relevance of the results are discussed. LD/MS of organic dyes typically produces intact molecular ions (as well as protonated, sodiated, and deprotonated ions). LD/MS of inorganics produces a variety of cluster ions representing the surface composition of the sample, suggesting the potential for elemental analysis using LD/MS. This thesis demonstrates the value and versatility of LD/MS in chemical characterization. |
