Post‐chromatographic TOF‐SIMS identification of diterpenes

Abstract

AbstractMixture of two diterpenes was separated by thin layer chromatography (TLC) on different substrates and then analysed with time‐of‐flight secondary ions mass spectrometry (TOF‐SIMS). Abietic (AA) and gibberellic acids (GA) were separated on three different chromatographic thin layers: monolithic silica chromatographic ultra‐thin layer (A), aluminium backplate modified silica gel thin layer (B) and commercially available Raman spectrometric thin layer (C). GA is more polar and is stronger retained near the start of layer while AA moves with mobile phase front (ethanol–water, 40:60, v/v). Primary detection with UV lamp was possible only for AA. TOF‐SIMS macroscans of chromatographic thin layer surfaces have been collected for most intensive positive or negative charged ions. The most applicable TOF‐SIMS analytical signal response was obtained from analytes separated on monolithic silica and aluminium backplate modified thin layer surface. Thin layer produced for on‐line Raman spectroscopy is only partially suitable for TOF‐SIMS analysis and this substrate does not support construction of negative ions macroscans. The suitability of the substrates for post‐chromatographic TOF‐SIMS analysis was found in order: Raman spectroscopy thin layers < monolithic silica < and aluminium backplate modified surface—for negative ion macroscans. For positive‐ion macroscans formation, the order is as follows: Raman spectroscopy layer < aluminium backplate modified surface < and monolithic silica. The results obtained from these analyses should be applied in future coupling of TOF‐SIMS with microcolumn high‐performance liquid chromatography (µHPLC), online. TOF‐SIMS was chosen for its outstanding capabilities in molecular surface analysis and surface imaging, in particular, of mono‐, di‐, seskviterpenes. Copyright © 2006 John Wiley & Sons, Ltd.