Used primarily in pharmaceutical research as a metabolite of fluphenazine, an antipsychotic agent. It serves as a reference standard in analytical testing to assess the metabolism, stability, and impurity profiles of fluphenazine in drug formulations. Commonly employed in HPLC and mass spectrometry studies to identify and quantify metabolic byproducts in biological samples. Also relevant in studies evaluating the pharmacokinetics and bioavailability of phenothiazine derivatives.