IMAGING OF THIN-LAYER CHROMATOGRAMS USING MATRIX ASSISTED LASER DESORPTION/IONIZATION MASS-SPECTROMETRY/

A new approach for directly coupling thin-layer chromatography (TLC) w ith matrix-assisted laser desorption/ ionization mass spectrometry is introduced. To avoid excessive analyte spreading along a TLC plate, a matrix layer was first generated on a different substrate, from which it was transferred to the plate. The transfer was accomplished by pres sing the matrix onto a previously wetted TLC plate. Successful direct imaging of silica gel TLC plates with high spatial resolution (250-500 mu m) and high sensitivity has been demonstrated for several compound s, including rhodamine B, guinea green B, bradykinin, and angiotensin II, using nanogram quantities of analyte, The ultimate spatial resolut ion was estimated to be similar to 50 mu m due to matrix heterogeneity and the minimum laser beam diameter required to produce good signal i ntensity. The current protocol induced minimal analyte planar diffusio n (similar to 0.5 mm) and resulted in an absolute detection limit in t he picogram range.