The behavior of some phenothiazines and their demethylated derivatives in reversed-phase liquid chromatography.

Three selected phenothiazines and their demethylated derivatives are chromatographed on different C18 bonded reversed-phase liquid chromatography columns. A quadratic equation fits the relationship log k versus the organic modifier percentage. When acetonitrile is the organic modifier, the demethylated derivative is eluted before the parent compound, whereas it is eluted after when methanol is the organic modifier. The log kw values are therefore different. Selectivity between the metabolite and the parent compound is higher with methanol.