Laser Desorption Mass Spectrometry of Complex Biomolecules at High Laser Power Density

The laser microprobe mass analyzer LAMMA® 500 originally designed for the extremely sensitive tracing of elements and molecules in microsamples and tissue obviously comprises soft ionization characteristics allowing the mass spectrometric analysis of ther-molabile, non-volatile high-molecular-weight biomolecules [1] . The possibilities and limitations of getting information on molecular weight and chemical structure are demonstrated with the aid of positive and negative ion LD mass spectra of two free lipid A samples isolated from Proteusmirabilis bacteria which were grown at different temperatures. Furthermore, a model of the laser-induced desorption process from organic solids is derived based on the experimental experience with LAMMA 500 applied to a large number of chemically different compounds and on the influence of laser power density and sample conditions (geometry, compactness).