Selectivity differences for C18 and C8 reversed-phase columns as a function of temperature and gradient steepness I.: Optimizing selectivity and resolution

Four experimental runs where temperature T and gradient time t(G) are varied allow the computer-prediction of reversed-phase liquid chromatographic (RPLC) separation for different combinations of temperature and gradient time. This in turn can provide significant changes in selectivity and a resulting optimization of separation. If this procedure is repeated for different columns, additional control over selectivity and resolution becomes possible. The simultaneous variation of T and t(G) for columns from different sources was studied for two samples, as a means of evaluating the general advantage of this approach for RPLC method development. Changes in relative retention with T were found to be approximately constant for different values of t(G) and for different RPLC columns; similarly, changes in relative retention with t(G) were roughly independent of changes in temperature or the column. The latter relationships can be useful in matching ("tracking") peaks between runs during method development based on the present approach, as well as for other applications discussed in here and in Part II. (C) 2000 Elsevier Science B.V. All rights reserved.