Solid-phase microextraction (SPME) is a popular sample preparation technique that involves the preconcentration of analytes from a variety of matrices, often without the need for sample pre-treatment. Our group has been focusing on the practical and fundamental aspects of SPME, particularly in the development of highly selective sorbent coatings using polymeric ionic liquids (PILs). The ability to alter the chemical composition of these materials by the means of synthesis or by employing different cation/anion combinations has produced coatings that exhibit superior selectivity for target analyte(s) in various sample matrices.
We have developed an on-fiber UV co-polymerization route to chemically immobilize crosslinked PILs on various SPME supports. The method requires no organic dispersive solvent and is much more rapid compared to traditional SPME fiber preparation methods. Additionally, the crosslinked PIL-based SPME coatings possess excellent thermal and mechanical stability, and are applicable in both headspace and direct-immersion SPME. In one application, polar crosslinked PIL-based SPME coatings were developed for the extraction of polar analytes from complex water samples. Excellent analytical performance and good recovery of these analytes can be obtained using these novel coatings, even after multiple direct-immersion experiments. We are also studying PIL-based bucky gel sorbent coatings in which single-walled carbon nanotubes (CNTs) have been successfully dispersed within the IL prior to free-radical polymerization (see figure below). The high surface area, high mechanical strength, and high thermal stability of CNTs make them particularly attractive when making PIL-hybrid coatings for SPME. Compared to the neat PIL-based sorbent coating, the PIL bucky gel sorbent coatings demonstrated higher extraction efficiency for polycyclic aromatic hydrocarbons. On-going work in our lab is focused on using SPME as a platform to study the way in which molecules interact with carbon nanotubes.