Systematic investigations of peak distortions due to additives in supercritical fluid chromatography.

•Mechanistic modelling of separation of basic drugs accounting for additive effects.•Amine additives generally sharpen solute peaks but may also deform preparative peaks.•Deformed solute peaks due to co-elution with additive perturbation zones.•Amine additives can promote multilayer adsorption causing deformed solute peaks.•Stronger multilayer tendency using primary amine additives compared higher order.