Separation of ternary systems of hydrophilic ionic liquid with miscible organic compounds by RPLC with refractive index detection

• Published in: Journal of separation science 2008-04, Vol.31 (6-7), p.1060-1066
• Main Authors: Zhang, Dongli, Deng, Yuefeng, Li, Chuanbi, Chen, Ji
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Ionic liquids; Other chromatographic methods; Relative standard deviation; Resolution; RPLC-RI
• ISSN: 1615-9306; 1615-9314
• DOI: 10.1002/jssc.200700634

A rapid and simple analytical method was developed for the simultaneous and quantitative determination and separation of hydrophilic imidazolium ionic liquids (ILs) (1-butyl-3-methylimidazolium chloride, [C₄mim]Cl; 1-hexyl-3-methylimidazolium chloride, [C₆mim]Cl; 1-octyl-3-methylimidazolium chloride, [C₈mim]Cl; 1-allyl-3-methylimidazolium chloride, [Amim]Cl; or 1-allyl-3-methylimidazolium bromide, [Amim]Br) with miscible ethyl acetate and EtOH and their mixtures using reverse phase liquid chromatography coupled with refractive index detection (RPLC-RI). The influence of 60 to 100% (volume percentage) methanol in the mobile phase on the IL systems ([C₄mim]Cl, [C₆mim]Cl, [C₈mim]Cl, [Amim]Br, or [Amim]Cl)-ethyl acetate-EtOH was investigated. The optimum mobile phase for the system [C₈mim]Cl-ethyl acetate-EtOH, [C₄mim]Cl-ethyl acetate-EtOH, [Amim]Br-ethyl acetate-EtOH and [Amim]Cl-ethyl acetate-EtOH was methanol/water (60:40, v/v), and methanol/water (70:30, v/v) for [C₆mim]Cl-ethyl acetate-EtOH. Under optimum mobile phase conditions for each system, the RSD of the retention time ranged from 0.02 to 0.04%, and the RSDs of the peak area percent ranged from 0.23 to 1.85%, which showed good reproducibility of the RPLC-RI method. The RPLC-RI method can determine IL, ethyl acetate, and EtOH simultaneously in 5 min, and the analytes, especially IL, can be eluted completely. The results show that the RPLC-RI method can be used to separate and determine ILs in mixtures with organic compounds simultaneously and quantitatively.