| AVS 60th International Symposium and Exhibition | |
| Applied Surface Science | Monday Sessions |
| Session AS-MoA |
| Session: | Analyses Using Novel Ion Beams |
| Presenter: | Y. Cui, University of Illinois at Chicago |
| Authors: | Y. Cui, University of Illinois at Chicago C. Bhardwaj, University of Illinois at Chicago S. Milasinovic, University of Illinois at Chicago R. Gordon, University of Illinois at Chicago L. Hanley, University of Illinois at Chicago |
| Correspondent: | Click to Email |
Matrix assisted laser desorption ionization and secondary ion mass spectrometry are the two dominant mass spectrometric imaging methods, but signal stability in the former degrades when spatial resolution increases, while the latter can suffer from extensive fragmentation that complicates peak identification. Laser desorption with ultrashort pulses can remove material from a solid with minimal damage to the remaining sample [Milasinovic, et al., Anal. Chem. 84 (2012) 3945]. Furthermore, laser desorbed neutrals can undergo soft postionization by vacuum ultraviolet (VUV) radiation for subsequent detection by MS. Here, we demonstrate the small molecule imaging capability of this method on intact microbial biofilms. Baker’s yeast and E. coli biofilms grown on polycarbonate membranes were studied using a previously reported instrument [Cui, et al., Rev. Sci. Instrum. 83 (2012) 093702] equipped with a long Rayleigh range focusing lens and a VUV postionization source [Bhardwaj, et al., Anal. Bioanal. Chem. (2012) http://dx.doi.org/10.1007/s00216-012-6454-0]. Comparisons were made between laser desorption using direct ionization and VUV postionization. The effects of nanosecond vs. femtosecond desorption pulse lengths were also compared. The results from fs and ns pulses were similar, differing mostly in their relative peak intensities, presumably because of the dependence of the desorption mechanism on laser pulse length. Different delays between the desorption and VUV lasers were also investigated. The imaging capability was demonstrated using baker’s yeast and E. coli cocultured biofilms. Results showed significant differences between films containing yeast, E. coli, and a mixture. Although these capabilities were applied here to intact biological samples, they can be extended to a wide variety of materials including polymers, metals, semiconductors, and insulators.