New approaches to coupling TLC with TOF-SIMS

A new hyphenated technique that enables coupling of thin-layer chromatography (TLC) with time-of-flight secondary-ion mass spectrometry (TOF-SIMS) has been used for identification of gibberellic acid, as model analyte. TOF-SIMS has outstanding capabilities for molecular surface analysis, trace metal determination on surfaces, and surface imaging. When TLC and TOF-SIMS are coupled on-line, the chromatographic thin layer must be modified to avoid TOF-SIMS background signal activity from the chromatographic material or solvents used. Two different types of TLC plate were used for coupling with TOF-SIMS. The first was an aluminum backed plate modified to form a universal porous TLC-TOF-SIMS coupling interface. The second was a commercially available plate with a monolithic silica layer. Low TOF-SIMS background signal intensity, surface homogeneity, and integral analyte transfer characterize this novel TLC-TOF-SIMS interface. TOF-SIMS images of the TLC surfaces with separated gibberellic acid were used for identification purposes. SIMS enables analyte detection with high mass resolution at a level of concentration not achieved by other methods. The system described can easily be coupled with dynamic microcolumn high-performance liquid chromatography (mu HPLC).