Analysis of Linear Regressions Applied to Water‐Methanol Eluents Modified with Ionic Liquid

Abstract

Five equations, two linear (Soczewinski and Langmuir‐type) and three multiple linear have been applied for investigation of the influence of 1‐butyl‐3‐methylimidazolium tetrafluoroborate ionic liquid modifier on the retention eluent composition relationships in reversed‐phase high performance liquid chromatography. In the experiment, five solutes belonging to amino acids, namely N‐carbobenzyloxy‐D‐phenylalanine, D‐tryptophan, and orthro‐, meta‐, and para‐isomers of amino benzoic acid were tested. Statistical evaluation of models of chromatographic retention was performed and discussed. This study shows that Soczewinski and Langmuir‐type equations are able to describe chromatographic retention of molecules which do not form stable ions in the aqueous, relatively precisely. At the same time, these models are not applicable for the description of N‐CBZ‐D‐phenylalanine retention, which exists in the water solution as anion and more complex models, considering that interactions between ionizable sample and eluent are required. Multiple linear regressions with two variables (methanol and ionic liquid modifier contents) improve significantly the description of N‐CBZ‐D‐phenylalanine retention.

Keywords:

• RP‐HPLC
• Retention model
• Mobile phase composition
• Modifier
• Ionic liquid

Acknowledgment

The authors are grateful for financial support from the Center for Advanced Bioseparation Technology, Inha University.