Polymeric ionic liquids as CO(2) selective sorbent coatings for solid-phase microextraction.

Two polymeric ionic liquids (PIL) were synthesized and employed as sorbent coatings in solid-phase microextraction (SPME) for the selective extraction of CO(2). The two coatings, poly(1-vinyl-3-hexylimidazolium) bis[(trifluoromethyl)sulfonyl]imide [poly(VHIM-NTf(2))] and poly(1-vinyl-3-hexylimidazolium) taurate [poly(VHIM-taurate)], exhibited varied selectivity toward CO(2) due to functional groups within in the PIL that imparted different mechanisms of CO(2) capture. Extraction efficiencies were compared to those of two commercial SPME fibers [poly(dimethylsiloxane) (PDMS) and Carboxen-PDMS]. The poly(VHIM-NTf(2)) PIL fiber exhibited comparable extraction efficiency at high CO(2) pressure compared to the Carboxen-PDMS fiber, even though the PIL-based fibers possessed much smaller film thicknesses. Calibration curves generated in pure CO(2) showed that the sensitivity of the poly(VHIM-NTf(2)) coating was comparable to that of the Carboxen-PDMS fiber with both PIL-based fibers exhibiting larger linear ranges and higher extraction-to-extraction reproducibility. The storage ability for selected fibers was examined and revealed that the PIL-based coatings exhibited superior capability in retaining the CO(2) sorbate on the fiber under different storage conditions, particularly for the poly(VHIM-taurate) PIL which reversibly captures CO(2) as a carbamate salt.