Date of Award


Degree Type


Degree Name

Master of Science




Dr. Robert H. Lipson

Second Advisor

Dr. John F. Corrigan

Third Advisor

Dr. J. Peter Guthrie


Since its inception over two decades ago matrix-assisted laser/desorption ionization (MALDI) mass spectrometry (MS) using either ultraviolet (UV) or infrared (IR) lasers, has become an important tool for the analysis of molecules of chemical and biological interest. Primarily, this is because MALDI-MS is a relatively "soft methodology which allows the ionization and detection of intact analytes with minimal fragmentation. Although MALDI mass spectrometry using visible wavelength lasers has been less studied it is expected to have several advantages over UV-MALDI and IR- MALDI. Many macromolecules of interest absorb UV-light but are transparent at visible wavelengths. In principle, visible-MALDI should be softer than UV-MALDI. Like UV- MALDI, visible-MALDI is also expected to require lower pulse energies than IR- MALDI. Furthermore, readily available pulsed visible laser sources such as the solid- state frequency-doubled Nd:YAG laser (532 nm output) are becoming relatively inexpensive and have longer operational lifetimes compared to standard UV devices. This thesis describes an exploration of possible organic molecules that can absorb 532 nm laser light and serve as matrices. Two classes of compounds considered: pyrromethene and Rhodamine laser dyes. The experiments carried out established that the Rhodamine (R) 610 laser dye is relatively stable; that is, it exhibits minimal fragmentation under 532 nm laser irradiation, and can ionize a selection of analytes. The chloride salt of R610 yielded the cleanest spectra making it a particularly good MALDI matrix candidate for detecting small molecular weight analytes. R575, a neutral laser dye, was found to be an effective absorber in binary matrices. Analyte ionization was achieved by combining this specific laser dye with either a proton donor (HC1 or CHCA), proton acceptor (NaOH), or alkali donor (NaTFA). A detection sensitivity as low as ~12 femtomole was determined using R575 as a component of an acidic or basic binary matrix.



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