Selectivity differences for C-18 and C-8 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 varie d allow the computer-prediction of reversed-phase liquid chromatographic (R PLC) separation for different combinations of temperature and gradient time . This in turn can provide significant changes in selectivity and a resulti ng optimization of separation. If this procedure is repeated for different columns, additional control over selectivity and resolution becomes possibl e. The simultaneous variation of T and t(G) for columns from different sour ces was studied for two samples, as a means of evaluating the general advan tage of this approach for RPLC method development. Changes in relative rete ntion with T were found to be approximately constant for different values o f t(G) and for different RPLC columns; similarly, changes in relative reten tion with t(G) were roughly independent of changes in temperature or the co lumn. The latter relationships can be useful in matching ("tracking") peaks between runs during method development based on the present approach, as w ell as for other applications discussed in here and in Part II. (C) 2000 El sevier Science B.V. All rights reserved.