Temperature effects on retention in reversed phase liquid chromatography

Multivariate experimental designs have been used to examine the effects of temperature, % organic mobile phase modifier, mobile phase pH, and stationary phase upon retention in reversed phase chromatography using packed capillary columns. Model compounds were naphthalene, acenaphthene, ibuprofen, butylparaben, diethyl phthalate, monoethyl phthalate, amitriptyline, propranolol, amphetamine, all-trans-retinol, 13-cis-retinol, and DL-leucine-DL-phenylalanine. Second to % organic modifier, the temperature exerted the greatest effect upon the retention of neutral compounds. The pH also had a major effect for acidic and basic compounds, for which the temperature was important for retention control at low and high pH for acids and bases, respectively. The type of stationary phase was not found to exert a significant effect for any of the tested compounds. A reversed temperature effect was found for the dipeptide leucine-phenylalanine at low pH and high % acetonitrile, resulting in increased retention at elevated temperatures. In all other cases, the retention decreased with increasing temperature.