Multimode Gradient Elution in Reversed-Phase Liquid Chromatography: Application to Retention Prediction and Separation Optimization of a Set of Amino Acids in Gradient Runs Involving Simultaneous Variations of Mobile-Phase Composition, Flow Rate, and Temperature

Abstract

The theory of multimode gradient elution in liquid chromatography involving combined gradients of the mobile-phase composition with flow rate and column temperature is presented, and a very simple stepwise method that allows for the calculation of the elution time of a sample solute under all gradient conditions is proposed. The theory is successfully applied to the separation of 12 o-phthalaldehyde derivatives of amino acids in eluting systems modified by acetonitrile. Average errors below 2.9% have been found in the retention prediction using the above method, which is supported by adequate models and algorithms capable of describing the chromatographic behavior of solutes upon changes in the separation factors, such as the modifier content, flow rate, and temperature.

Stationary-Phase Optimized Selectivity Liquid Chromatography: Development of a Linear Gradient Prediction Algorithm

“…Multiple approaches and algorithms were developed in the past in order to predict retention times under linear gradient conditions. − In all approaches, other parameters and aspects beside eq have to be considered. A mandatory parameter is thereby the dwell time, t dwell .…”

“…Furthermore, arbitrary decisions about sample components are eliminated, and accurate predictions of all retention times and selectivity factors can be obtained. The use of discontinuous or numerical integration approaches is currently well established in the chromatographic field. − …”

“…The use of discontinuous or numerical integration approaches is currently well established in the chromatographic field. [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]…”

Expressions for Multilinear Combined pH/Organic Solvent Elution of Ionizable Analytes in Reversed-Phase HPLC

“…High-performance liquid chromatography (HPLC) is a fundamental technique used in quantitative and qualitative applications, and numerous attempts have been made in order to model the retention at either isocratic or gradient conditions. − The most common gradient technique is the mobile phase gradient elution. However, especially for ionogenic analytes, the most crucial chromatographic parameter is the mobile phase pH, since it changes their dissociation degree.…”