Ionic liquid-mediated bis[(3-methyldimethoxysilyl)propyl] polypropylene oxide-based polar sol-gel coatings for capillary microextraction.

Two ionic liquids (IL), namely, 1-methyl-3-octylimidazolium chloride (MOIC) and trihexyltetradecylphosphonium tetrafluoroborate (TTPT) were used to prepare polar and nonpolar sol-gel coatings for capillary microextraction (CME). Bis[(3-methyldimethoxysilyl)propyl] polypropylene oxide (BMPO), containing sol-gel active terminal methoxysilyl groups and polar propylene oxide repeating units, was used to prepare polar sol-gel hybrid organic-inorganic coatings. Hydroxy-terminated poly(dimethyl-co-diphenylsiloxane) was used as the sol-gel active organic component for nonpolar sol-gel hybrid coatings. Compared to a sol-gel BMPO coating prepared without IL, the sol-gel BMPO coatings prepared with the use of both of these ILs provided more efficient extraction as is evidenced by more pronounced GC peak areas. The MOIC-mediated sol-gel BMPO coating provided larger GC peak areas compared to the TTPT-mediated sol-gel BMPO coating. Scanning electron microscopy results suggested that MOIC provided a more porous morphology of the sol-gel BMPO extraction media compared to that prepared with TTPT. Thus, individual ILs can affect the porosity of sol-gel materials to different degrees. Overall, the sol-gel BMPO coating prepared with the ILs could extract nonpolar to polar analytes directly from aqueous samples. Detection limits were on the order of nanograms per liter (1.9-330.5 ng/L) depending on the analyte class. Furthermore, the MOIC-mediated sol-gel BMPO coating demonstrated high thermal stability (330 degrees C), solvent resistance, and fast extraction equilibrium (10-15 min) for polar and moderately polar analytes.