Ethylammonium Acetate as a Mobile Phase Modifier for Reversed Phase Liquid Chromatography
- 139 Downloads
We have synthesized the low melting hygroscopic ionic liquid ethylammonium acetate (EAA) and characterized a concentrated solution of EAA as a reversed phase mobile phase replacement for organic solvents like methanol. This solution of EAA acts like an organic solvent with a polarity parameter (P’=6.0) similar to methanol (P’=5.1) but less than water (P’=10.2). A test mixture of salicylate, nitrofurantoin, and acetophenone was separated in this order on C1, C4, and C18 columns using an EAA modified aqueous mobile phase. On a C-18 column, the reduction in retention factor for acetophenone from about 20 to 2 as the % EAA is raised from 20–80% is similar to the same trend found using methanol. However, the retention order using methanol is first nitrofurantoin, then salicylate, and finally acetophenone. Log retention factor (k) versus the volume fraction of either EAA or methanol plots were linear indicating the solvent strength parameter for EAA was about 85% of that for methanol. Despite the relatively high viscosity of EAA, plate count values averaged only about 15% less for EAA as compared to methanol using the same mobile phase composition and could be raised by either working at a temperature above ambient or reducing the flow rate. EAA as a modifier allowed for faster separations of water-soluble vitamins on a reversed phase column designed for totally 100% aqueous mobile phases.
KeywordsColumn liquid chromatography Aqueous mobile phase modifier Ethylammonium acetate Water-soluble vitamins
Unable to display preview. Download preview PDF.
- Davis JM, Fox PA (2003) Chem Commun 11:1209–1212Google Scholar
- Adams CJ, Earle MJ, Roberts G, Seddon KR (1998) Chem Commun 19:2097–2098Google Scholar
- Vaher M, Koel M, Karjuland M, (2001) Chromatographia 53:S302–S306Google Scholar
- Yanes EG, Gratz SR, Baldwin MJ, Robison SE, Stalcup AM (2001) Anal Chem 73:3838–3844Google Scholar
- Mwongela SM, Numan A, Gill NL, Agbaria RA, Warner IM (2003) Anal Chem 75:6089–6096Google Scholar
- Mihkel K (2000) Proc Estonian Acad Sci Chem 49:145–155Google Scholar
- Wilkes JS, Zaworotko MJ (1992) J Chem Soc Chem Commun 13:1965Google Scholar
- Gladchikova, Y. N. (1964) Ref Zh Khim Abstract No. 141283Google Scholar
- Poole CF (2003) The Essence of Chromatography, Elsevier, Amsterdam, pps. 302, 303, 369Google Scholar