Application of ionic liquids in high performance reversed-phase chromatography

Comparison and evaluation of five types of imidazole-modified silica adsorbents for the removal of 2,4-dinitrophenol from water samples with the methyl group at different positions of imidazolium ring

The objective of this work was to improve the understanding the influence of the methyl group at different positions of imidazolium ring on the adsorption behaviors of imidazole-modified silica adsorbents. Five adsorbents named as SilprImCl, SilprM₁ImCl, SilprM₂ImCl, SilprM₄ImCl and SilprM₁M₂ImCl were synthesized using imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole and 1,2-dimethylimidazole, respectively. These adsorbents were characterized by scanning electron microscope, infrared spectra, thermogravimetric analysis, elemental analysis and BET analysis. Firstly, phenol, 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP) and 2,4-dinitrophenol (2,4-DNP) were used as adsorbates to investigate the selectivity of SilprImCl and its adsorption capacities followed the order of 2,4-DNP≫4-NP>2-NP≫3-NP>phenol. Therefore, 2,4-DNP was used to investigate the adsorption behaviors of the five adsorbents. It was inferred that the adsorbents are of primary anion-exchange and electrostatic nature. The electrostatic nature was affected significantly by the methyl group at different positions of imidazolium ring. The adsorbed amounts of 2,4-DNP decreased in the order of: SilprM₁M₂ImCl≈SilprM₁ImCl>SilprM4ImCl>SilprM₂ImCl>SilprImCl. The adsorption-elution experiments indicated that 2,4-DNP can be removed from aqueous solutions by a SilprM₄ImCl packed column and the recovery of 91.6% was obtained. The adsorbent could be regenerated and reused ten times at least by simple washings with HCl and water in turn.

Use of an immiscible diluent in ionic liquid / ion pair LC for the assay of an injectable analgesic

Injectable solutions used in treatment of intense pain are based on combinations of active ingredients such as metamizole sodium (MTZ), pitofenone hydrochloride (PTF) and fenpiverine bromide (FPB). The simultaneous chromatographic assay of such combinations poses difficulties due to their structural variety, highly polar character, and wide concentration ranges (500 mg mL−1 for MTZ, 2 mg mL−1 for PTF and 0.02 mg mL−1 for FPB). Fast hydrolysis of MTZ on aqueous dilution causes additional problems due to impurity (MTC) formation. Sodium hexane sulphonate (10 mM) was used as ion pairing agent for PTF, FPB and MTC in a mobile phase consisting of 48/52 (v/v) methanol and aqueous 0.2% triethylamine at pH=3. The ionic liquid 1-butyl-1-methyl-pyrrolidinium tetrafluoroborate (10 mM) was used as mobile phase additive to preserve the MTZ peak symmetry. The minor active ingredient FPB was selectively extracted into 1-octanol by ion pair formation with picric acid. A 20 µL aliquot of the organic layer was directly injected into the column.

Ionic liquid applications in peptide chemistry: synthesis, purification and analytical characterization processes

This review aims to provide a comprehensive overview of the recent advances made in the field of ionic liquids in peptide chemistry and peptide analytics.

New chiral imidazolium ionic liquids from isomannide

New chiral bis and mono-imidazolium ionic liquids derived from isomannide were synthesized. The structural features of the chiral organic cations impart a special arrangement of the chiral cavity. The new chiral chloride salts of isomannide derivatives are pivotal compounds for the synthesis of different organic ionic liquids. After metathesis different anions were associated to the chiral cations providing a new class of chiral ionic liquids.