A novel sample pretreatment method using supercritical fluids for the analysis of atmospheric environmental samples by means of time‐of‐flight secondary ion mass spectrometry

A novel sample pretreatment method was developed for time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis of organic matter in environmental particles. This method employs the supercritical fluid extraction (SFE) technique. In SFE, the extraction efficiencies of aliphatic and aromatic compounds are largely different from each other at a certain fluid condition, e.g. pressure and temperature. Two-step SFE (two fluid conditions) of diesel exhaust particles (DEPs) showed that n-alkanes and polycyclic aromatic hydrocarbons (PAHs) can be separately extracted by changing both the fluid pressure and temperature from low to high. This selective extraction was applied to the sample preparation of TOF-SIMS analysis, where n-alkanes are ‘unwanted’ constituents if PAHs are the analytical targets. The obtained TOF-SIMS spectrum of the particles after SFE was simplified and the mass peaks of PAHs were easily assigned, because n-alkanes were selectively removed in the SFE pretreatment. Copyright © 2006 John Wiley & Sons, Ltd.