Variation of anionic moieties of dicationic ionic liquid GC stationary phases: Effect on stability and selectivity

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Dicationic ionic liquids (DILs) are emerging as advanced stationary phases for high-temperature gas chromatography (GC).
• Their unique properties offer potential advantages over traditional phases for specific analytical challenges.

Purpose of the Study:

• To synthesize and characterize 14 novel DILs with fluorosulfonyl derivatized anions and two dications.
• To evaluate their thermophysical properties, polarity, and selectivity for GC applications.
• To assess their performance in analyzing biodiesel and bacterial fatty acid methyl esters (FAMEs).

Main Methods:

• Synthesis of 14 DILs based on two dications and seven fluorosulfonyl derivatized anions.
• Evaluation of thermophysical properties: melting point, viscosity, and thermal stability.
• GC column preparation and evaluation using Rohrschneider-McReynolds constants and FAME equivalent chain lengths.

Main Results:

• 13 DILs exhibited optimal properties for GC column preparation.
• DILs with symmetrical fluoroalkylsulfonyl and trifluorosulfonate anions demonstrated high polarity.
• Compared to polyethylene glycol phases, DILs reduced retention of apolar compounds and increased retention of polar compounds.
• Unique selectivities were observed for unsaturated FAMEs, polyaromatic hydrocarbons, and bacterial FAMEs.

Conclusions:

• The synthesized DILs represent a promising class of polar stationary phases for GC.
• Their tunable properties allow for unique selectivity, particularly for polar and unsaturated compounds.
• Successful application in biodiesel and bacterial FAME analysis highlights their practical utility.