Centennial Honors College
Western Illinois University
Undergraduate Research Day 2014
Poster Presentation
Adsorption Isotherms of Basic Drugs on Reversed Phase Liquid Chromatography
Using Ionic Liquids as Mobile Phase Additives
Bryin Davis and Lauren Ward
Faculty Mentor: Tarab Ahmad
Chemistry
Residual silanol groups in Reversed phase liquid chromatography cause band tailing
and asymmetrical peaks especially for basic compounds. Ionic liquids are used as
mobile phase additives in reversed phase high performance liquid chromatography RPHPLC to block the silanol activity. Therefore, they improve the peak shapes and they
remove the peak tailing. The retention mechanism of basic compounds on RPLC in the
presence of ionic liquids is not known yet. Therefore, we are using in this study
adsorption isotherms to determine the type of the interaction between the analytes,
stationary phase and the ionic liquids by studying the adsorption isotherms.
Determination of adsorption isotherms is an important step in the computer optimization
of separations. It is useful also to predict the band profiles in liquid chromatography
which reduces the cost, solvent consumption and the time needed for the separations.
Adsorption isotherms are also useful in studying the retention mechanism in liquid
chromatography. In this study, the adsorption isotherms of basic drugs are determined
on reversed phase liquid chromatography using an aqueous solution of an ionic liquid
and acetonitrile.
Adsorption isotherm data were collected using frontal analysis
experiments. The adsorption data for Amitripytline and Nortryptyline are modeled by biLangmuir and Langmuir models without and with using ionic liquids as mobile phase
additives respectively. The models were validated by calculating the band profiles using
the parameters of the isotherms. There was a good match between the experimental
and the overloaded band profiles