IR resonance-enhanced organic detection with two-step laser desorption time-of-flight mass spectrometry
We explore resonance-enhanced sample analysis with a prototype two-step laser desorption time-of-flight mass spectrometer (L2MS) to characterize the dependence of resonant desorption on the L2MS detection sensitivity. In L2MS, desorption and ionization of analyte is separated into two distinct steps: an IR laser desorbs surface material and a UV laser ionizes analyte from the resulting neutral plume. Desorption of analyte, including trace organic species, may be increased by coupling the wavelength of the desorption laser to IR absorption features associated with vibration transitions of minerals or organic functional groups. We demonstrate this effect on minerals relevant to icy bodies, doped with the aromatic amino acid tryptophan, and find a correlation between the optimal L2MS desorption laser wavelength for organic detection and the presence of vibrational transitions in the mineral substrate. We present the unique organic detection capabilities of the L2MS, and demonstrate the value of exploiting this resonant-enhanced desorption effect to optimize the detection of organics on other planetary bodies.