Analysis of Morpholinium Ionic Liquid Cations by Hydrophilic Interaction Columns Coupled with Indirect UV Detection

Abstract

A method was developed for the separation and detection of morpholinium ionic liquid cations by hydrophilic interaction column combined with indirect ultraviolet detection using imidazolium ionic liquids as ultraviolet absorbents in high-performance liquid chromatography. The effects of the ultraviolet absorbents, organic solvents, and the pH value of the aqueous solution in the mobile phase for the determination of morpholinium cations were investigated by using a hydrophilic column with carbamoyl group as the analytical column. The retention and detection behavior of morpholinium cations was discussed. The suitable chromatographic conditions were 0.8 mmol/L 1-ethyl-3-methyl-imidazolium tetrafluoroborate aqueous solution (pH 3.5 adjusted with acetic acid)/acetonitrile (45/55, v/v) as the mobile phase and a detection wavelength of 210 nm. Under these conditions, the baseline separation of N-methyl-N-ethyl-morpholinium cation ([MEMo] + ) and N-methyl-N-propyl-morpholinium cation ([MPMo] + ) was successfully achieved in 15 min. The detection limits of [MEMo] + and [MPMo] + were 0.595 and 0.531 mg/L, respectively. Relative standard deviations were less than 0.2%. This method has been successfully applied to the analysis of morpholinium ionic liquid samples synthesized in chemical laboratories, which is simple, reliable, and practical.

Ionic liquids as mobile phase additives for determination of thiocyanate and iodide by liquid chromatography

“…In recent years, the applications of ILs in the fields of GC stationary phases [12], LC stationary phases [13][14][15][16][17][18] and mobile phase additives [19,20] have received increasing attention. There are some reports on the analysis of organic substances such as alkaloids [21][22][23][24][25] and metal ions [26][27][28] by using ionic liquids as mobile phase additives, but there are few reports on the analysis of anions [29,30] which needs to be further studied extensively.…”