An appraisal of the chemical and thermal stability of silica based reversed-phase liquid chromatographic stationary phases employed within the pharmaceutical environment.

Mobile phase pH and temperature are major factors in determining retention, selectivity and chromatographic performance of ionizable compounds. This imposes a requirement that stationary phases must ideally be stable in both acidic and basic conditions coupled with good thermal stability, in order to be able to chromatograph these compounds in either their ionized or ion-suppressed modes. The development of a range of new high and/or low pH stable silica based RPLC stationary phases (including sub-2 μm fully porous and sub-3 μm fused core-shell materials), which are specially designed for the analysis of ionizable compounds and their chemical and thermal stability is reviewed. The ability to utilize both pH and temperature as selectivity variables allows the chromatographer to exploit a much wider method development design space including previously prohibited alkaline conditions. This greatly increases the probability of satisfying the desired chromatographic selectivity and performance criteria.