Development and validation of a procedure for the determination of minoxidil in hair-regrowth formulations using two variants of capillary zone electrophoresis

A high performance capillary electrophoresis method was developed and validated for purity assessment of minoxidil bulk drug and for determination of minoxidil in Rogaine®. The principal use of the method was in analyzing illicit minoxidil-containing hair-regrowth samples. Although validated for Rogaine, the procedure proved equally viable on illicit minoxidil-containing preparations. The developed method fulfilled the goal of providing an orthogonal technique to HPLC for confirmation of the presence of minoxidil in these imitations. The method was validated on two instruments, one utilizing EK injection, the other gravity injection. It is selective for minoxidil, which is separated from known process impurities and the single degradation impurity. Validation figures of merit for linearity/recovery (accuracy) and precision were in accordance with current expectations for method validation.