COMBINED USE OF TEMPERATURE AND SOLVENT STRENGTH IN REVERSED-PHASE GRADIENT ELUTION .2. COMPARING SELECTIVITY FOR DIFFERENT SAMPLES AND SYSTEMS

A change in temperature (T) or gradient steepness (b) can result in ch anges in reversed-phase selectivity (alpha). The magnitude of these ch anges in alpha will vary with ether separation conditions (column, pH, etc.) and with sample type. In this paper, selectivity changes as a f unction of T and b are discussed and a simple treatment that allows ch anges in selectivity to be compared quantitatively for different sampl es and HPLC conditions is developed. Following papers in this series w ill apply this theory to arrive at conclusions concerning the use of t emperature and gradient steepness in HPLC method development. The pres ent treatment assumes that gradient-steepness selectivity (measured by the parameter S) does not change significantly with temperature. Data for a wide range of compound types and conditions are provided in sup port of this assumption.