Band deformation in non-isocratic liquid chromatography

• Sources of peak deformation in solvent gradient were analyzed.
• Gradient shape distortion due to adsorption of mobile phase components was illustrated.
• Effect of column thermal heterogeneity on band deformation was shown.
• Equilibrium Theory and experimental data were used to elucidate the underlying mechanisms.

Peak deformation is a plague in both analytical and preparative chromatographic separations. The phenomenon may be particularly pronounced in non-isocratic separations, which involve solvent or temperature gradient. Solvent gradient can be exploited for column loading as well as elution of sample components. In the former case the solvent environment of the sample is different than the mobile phase, whereas in the latter one the mobile phase composition is varied during chromatographic elution. Temperature gradient can be used to alter adsorption behavior of eluities in temperature-sensitive chromatographic systems. It may also arise from column thermal heterogeneity caused by viscous friction of the mobile phase or improper thermostatting of the column.In this review we described typical sources of peak tailing in non-isocratic chromatography including solvent and temperature gradients, and elucidated underlying mechanisms of this phenomenon. The analysis was supported by theoretical predictions based on equilibrium theory, dynamic simulations, and experimental illustrations.