Exploring better column selectivity choices in ultra-high performance liquid chromatography using quality by design principles.

An older method for amlodipine was reworked with the goal to reduce the analysis time of 60min below 6min. To select the best column for short and robust analysis, 9 different UHPLC column chemistries were investigated using 3-dimensional resolution spaces based on 12 experiments using modelling software. The main variables used were gradient time (tG), temperature (T) and the pH of eluent A. The best critical resolution was calculated and located in a 3-dimensional space in an automated fashion and the corresponding best experiments were carried out. The work (9×12=108 runs) was finished with an UHPLC instrument in less than 24h. The comparison between predictions and real experiments showed an excellent correlation with differences typically less than 0.04min (<3s) in average, although the set points were located at quite different conditions on gradient times, pH's and temperatures for the individual columns. All columns could perform the required baseline separation at their individual best working points with satisfactory results.