Published:Journal of Chromatographic Science,
ISSN 0021-9665Volume
38, Number 11, November 2000, pp. 503-511
Characterizing
the Selectivity of Stationary Phases and Organic Modifiers in Reversed-Phase
High-Performance Liquid Chromatographic Systems by a General Solvation Equation
Using Gradient ElutionChau
My Du1,*, Klara Valko2, Chris Bevan2, Derek Reynolds2, and Michael H. Abraham1
1 Department of Chemistry, University College London, 20 Gordon Street, London
WC1H 0AJ, U.K. and 2Physical Sciences, GlaxoWellcome Medicines Research Centre,
Stevenage, Herts SG1 2NY, U.K.
Retention
data for a set of 69 compounds using rapid gradient elution
are obtained on a wide range of reversed-phase stationary phases and organic
modifiers. The chromatographic stationary phases studied are Inertsil (IN)-ODS,
pentafluorophenyl, fluoro-octyl, n-propylcyano, Polymer (PLRP-S 100), and hexylphenyl.
The organic solvent modifiers are 2,2,2-trifluoroethanol (TFE); 1,1,1,3,3,3-hexafluoropropan-2-ol
(HFIP); isopropanol; methanol (MeOH); acetonitrile (AcN); tetrahydrofuran; 1,4-dioxane;
N,N-dimethylformamide; and mixed solvents of dimethylsulfoxide (DMSO) with AcN
and DMSO with MeOH (1:1). A total of 25 chromatographic systems are analyzed
using a solvation equation. In general, most of the systems give reasonable
statistics. The selectivity of the reversed phase-high-performance liquid chromatographic
(HPLC) systems with respect to the solute’s dipolarity–polarity, hydrogen-bond
acidity, and basicity are reflected in correspondingly large coefficients in
the solvation equation. We wanted to find the most orthogonal HPLC systems,
showing the highest possible selectivity difference in order to derive molecular
descriptors using the gradient retention times of a compound. We selected eight
chromatographic systems that have a large range of coefficients of interest
(s, a, and b) similar to those found in water–solvent partitions used previously
to derive molecular descriptors. The systems selected are IN-ODS phases with
AcN, MeOH, TFE, and HFIP as mobile phase, PLRP-S 100 phase with AcN, propylcyano
phase with AcN and MeOH, and fluorooctyl phase with TFE. Using the retention
data obtained for a compound in the selected chromatographic systems, we can
estimate the molecular descriptors with the faster and simpler gradient elution
method.
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