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

Abstract 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 chromatogrpahy, including thin‐layer chromatography and electrophoresis.