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Column equilibration effects in gradient elution in reversed-phase liquid chromatography.
A Pappa-Louisi1, P Nikitas, P Agrafiotou
1Laboratory of Physical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece. apappa@chem.auth.gr
Journal of Chromatography. A
|June 27, 2006
Summary
This study investigates column equilibration in reversed-phase liquid chromatography (RPLC) for amino acids. Deviations between predicted and actual retention times were observed, leading to a proposed correction method for gradient elution theory.
Area of Science:
- Analytical Chemistry
- Chromatography Science
Background:
- Reversed-phase liquid chromatography (RPLC) is crucial for analyzing amino acids.
- Gradient elution in RPLC requires precise column equilibration for accurate retention times.
Purpose of the Study:
- To evaluate column equilibration effects in RPLC using linear and stepwise gradients.
- To investigate deviations between theoretical and experimental retention times for underivatized amino acids.
- To propose a method for correcting retention time discrepancies in gradient elution.
Main Methods:
- Application of fundamental equations for linear and stepwise gradient elution in RPLC.
- Analysis of underivatized amino acid mixtures in aqueous mobile phases modified with 2-propanol, acetonitrile, and methanol.
- Examination of column equilibration effects and retention time deviations.
Main Results:
- Systematic deviations between experimental and calculated retention times were observed across all mobile phase modifiers.
- Deviations were most prominent with 2-propanol, reduced with acetonitrile, and negligible with methanol.
- Discrepancies occurred shortly after mobile phase composition changes and diminished exponentially over approximately 5 minutes.
Conclusions:
- Column equilibration significantly impacts retention time accuracy in RPLC gradient elution.
- A method is proposed to correct calculated retention times based on observed experimental deviations.
- Understanding these discrepancies is vital for improving chromatographic resolution and data reliability.