Investigation of critical factors for the resolution of SR695, a key impurity, from efavirenz in the reversed-phase assay of efavirenz dosage forms.

An investigation of the critical factors effecting the resolution of SR695 from efavirenz in the assay of efavirenz by reversed-phase HPLC was performed. This study was implemented to address the inability of a subset of the Zorbax SB-CN columns used in this method to adequately perform this separation, which were otherwise indistinguishable from columns of this type that could. In this study, column temperature, detector time-constant, pre-gradient isocratic hold-time, pre-column mixing volume, column, and HPLC type were considered.