Analysis of Components of Ionic Liquids on Zodiac HST TH Column

Ionic liquids are salts that exist in a liquid state at or near room temperature. These compounds are typically composed almost entirely of ionic species, with over 99.99% of the liquid in an ionic rather than molecular form. Room-temperature ionic liquids commonly feature bulky cations such as substituted imidazolium and a wide range of organic or inorganic anions like chloride, iodide, tetrafluoroborate, hexafluorophosphate, bistriflimide, triflate, and tosylate. Due to their unique properties, ionic liquids are frequently employed as solvents in organic synthesis.

When isolating products from ionic liquids, it becomes necessary to analyze residual ionic liquid content. Traditional chromatography techniques are often ineffective for this purpose due to the contrasting ionic and hydrophobic characteristics of the cationic and anionic components.

A robust and universal method for analyzing ionic liquids has been developed using the Zodiac HST TH mixed-mode HPLC column. This column, featuring embedded positive and negative ionic groups, allows simultaneous retention and separation of both cationic and anionic components based on a combination of ionic and hydrophobic interactions. The method is suitable for the quantitative analysis of a wide range of ionic liquids containing both organic and inorganic ions.

Retention time of the basic component can be effectively tuned by adjusting pH, while more strongly anionic or hydrophobic counter-ions may require higher buffer concentrations for optimal separation. Detection can be achieved using UV, ELSD, or LC/MS, making this approach versatile for various applications in analytical and preparative workflows.