Date of Award


Degree Type


Degree Name

Master of Science




Dr. Robert H. Lipson


Matrix-free desorption/ionization on porous silicon (DIOS) has been used in this work to detect low molecular weight compounds by mass spectrometry. Post-ionization of neutral particles is a promising alternative technique for improving parent ion yields, particularly if gaseous neutrals can be ionized using a single photon ionization (SPI) source. In this thesis the high sensitivity of VUV laser SPI was combined with the excellent desorption capabilities of DIOS for the first time. This method is labeled SPI-DIOS-MS. First, a home-built apparatus combining electrochemical etching with laser irradiation was developed to produce microcolumn arrays on Si surfaces as a matrix-free DIOS-MS substrate. These surfaces have longer storage times, and are more damage-resistant to repeated laser exposure during DIOS-MS experiments than porous Si surfaces formed by galvanostatic etching alone. Second, four low-molecular-weight analytes with masses ranging from 360 Da to 2093 Da were analyzed to examine the potential application of silicon microstructured arrays as substrate for DIOS-MS. The lowest limitation of DIOS-MS detection for one of the compounds, the peptide Dalargin, was found to be 0.32 ± 0.04 pmol. Lastly, Dalargin was selected as a prototypical analyte for SPI detection using a VUV laser having a 118 nm (10.5 eV) output. The analyte signal showed an approximately 80% enhancement over its DIOS signal without post-ionization.



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