Preparation and application of ionic liquid-coated fused-silica capillary fibers for solid-phase microextraction

A simple and cost effective solid-phase microextraction device has been developed. Fused-silica capillaries were etched with ammonium hydrogen difluoride prior to coating with an ionic liquid. For comparison, both a bare fused-silica capillary and one pretreated with a Nafion membrane were coated with the ionic liquid. All three coated capillaries were employed for the head space microextraction of polycyclic aromatic hydrocarbons (PAHs) which were then separated with an established GC system. Efforts to optimize the extraction process indicated that the etched fiber displayed the most efficient extraction, giving not only highly reproducible extraction results but also greater extraction efficiency. The Nafion membrane-supported fiber was inferior to the etched fiber, while the untreated fused-silica had the lowest extraction efficiency. The Nafion membrane contains negatively charged sulfonate groups, and the increase in ionic liquid binding was due to electrostatic attractive forces. However, due to the hydrophobic interactions of the PAHs with the polymer matrix in the Nafion membrane, a more complex adsorption/desorption mechanism might reduce the efficiency. The established method was successfully applied for the analysis of PAHs released from burning of mosquito coil incense.