Ionic Liquids as Porogens in the Microwave-Assisted Synthesis of Methacrylate Monoliths for Chromatographic Application

Brenda Singco, Chen-Lan Lin, Yi-Jie Cheng, Yung-Han Shih, Hsi-Ya Huang

Anal Chim Acta. 2012 Oct 9;746:123-33.

PMID: 22975189

Abstract:

Several imidazolium-based ionic liquids (ILs) with varying cation alkyl chain length (C(4)-C(10)) and anion type (tetrafluoroborate ([BF(4)](-)), hexafluorophosphate ([PF(6)](-)) and bis(trifluoromethylsulfonyl)imide ([Tf(2)N](-))) were used as reaction media in the microwave polymerization of methacrylate-based stationary phases. Scanning electron micrographs and backpressures of poly(butyl methacrylate-ethylene dimethacrylate) (poly(BMA-EDMA)) monoliths synthesized in the presence of these ionic liquids demonstrated that porosity and permeability decreased when cation alkyl chain length and anion hydrophobicity were increased. Performance of these monoliths was assessed for their ability to separate parabens by capillary electrochromatography (CEC). Intra-batch precision (n=3 columns) for retention time and peak area ranged was 0.80-1.13% and 3.71-4.58%, respectively. In addition, a good repeatability of RSD(Retention time)=<0.30% and ~1.0%, RSD(Peak area)=<1.30% and <4.3%, and RSD(Efficiency)=<0.6% and <11.5% for intra-day and inter-day, respectively exemplify monolith performance reliability for poly(BMA-EDMA) fabricated using 1-hexyl-3-methylimidazolium tetrafluoroborate ([C(6)mim][BF(4)]) porogen. This monolith was also tested for its potential in nanoLC to separate protein digests in gradient mode. ILs as porogens also fabricated different alkyl methacrylate (AMA) (C4-C18) monoliths. Furthermore, employing binary IL porogen mixture such as 1-butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim][BF(4)]) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(4)mim][Tf(2)N]) successfully decreased the denseness of the monolith, than when using [C(4)mim][Tf(2)N] IL alone, enabling a chromatographic run to be performed with 1:1 ratio produced baseline separation for the analytes. The combination of ILs and microwave irradiation made polymer synthesis very fast (~10min), entirely green (organic solvent-free) and energy saving process.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP244193508	1-Hexyl-3-methylimidazolium tetrafluoroborate		244193-50-8	Price