DOPED GELATIN FILMS AS A MODEL MATRIX FOR MOLECULAR SECONDARY ION MASS-SPECTROMETRY STUDIES OF BIOLOGICAL SOFT-TISSUE

Porcine gelatin films doped with a number of biological compounds at v arious concentrations and prepared by spin-casting have been used as m odel biological tissue matrices for studying organic ion emission in m olecular secondary ion mass spectrometry. For many compounds, portions of the working curves were found to be linear over several orders of magnitude in concentration. Detection limits for the analyzed compound s were in the parts per million range for several organic salt compoun ds but high (0.1 wt%) for others. Owing to the presence of a significa nt chemical background, the poorest detection limits were generally ob tained from compounds with low molecular weights. Secondary ion yield matrix effects, indicated by a reduction in ionization efficiency at h igher concentrations, were observed for several organic salt compounds .