Temperature Pulsing for Controlling Chromatographic Resolution in Capillary Liquid Chromatography Tim J. Causon,† Hernan J. Cortes,†,‡ Robert A. Shellie,† and Emily F. Hilder*,† †
Australian Centre for Research on Separation Science, School of Chemistry, University of Tasmania, Private Bag 75, Hobart, Tasmania, Australia, 7001 ‡ HJ Cortes Consulting LLC, Midland, Michigan 48642, United States S Supporting Information *
ABSTRACT: In this study we introduce the implementation of rapid temperature pulses for selectivity tuning in capillary liquid chromatography. Short temperature pulses improved resolution in discrete sections of chromatograms, demonstrated for ion-exchange chromatography (IC) and hydrophilic interaction chromatography (HILIC) modes. Using a resistively heated column module capable of accurate and rapid temperature changes, this concept is first illustrated with separations of small anions by IC using a packed capillary column as well as a series of nucleobases and nucleosides by HILIC using a silica monolithic column with zwitterionic functionality (ZIC-HILIC). Both positive (increasing temperature) and negative temperature pulses are demonstrated to produce significant changes in selectivity and are useful approaches for improving resolution between coeluted compounds. The approach was shown to be reproducible over a large number of replicates. Finally, the use of temperature gradients as well as other complex temperature profiles was also examined for both IC and HILIC separations.
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he role of temperature in controlling selectivity for liquid chromatography (LC) has been historically viewed as less useful than variation of the eluent strength (e.g., the amount of organic modifier). However, numerous studies using modern instrumentation and stationary phases with improved thermal stability have demonstrated the benefits of elevated temperatures and temperature control for LC.1−4 Although most of these studies have focused on the use of elevated temperatures
