Imaging analysis and selected sequence monitoring of small peptides using planar chromatography/secondary ion mass...

Mixtures of enkephalins and bradykinins contained on silica gel thin-layer chromatograms were imaged by secondary ion mass spectrometry. Spatial profiles of the sample distribution in the chromatographic plane were determined using a precision manipulator that moves the sample into and out of the primary beam generated in a liquid metal gallium source. For instance, spatial profiles are conveniently measured by monitoring the protonated molecule [M + H]+ of each compound or, in a selected-sequence monitoring experiment, by monitoring a sequence ion common to the members of each peptide group. The latter experiment is useful for quick location and identification of a class of peptides separated by planar chromatography, including thin-layer chromatography and electrophoresis.