Determination of haloperidol and reduced haloperidol in human serum by liquid chromatography after fluorescence labeling based on the Suzuki coupling reaction

A simultaneous method for the determination of haloperidol (HP) and its metabolite, reduced haloperidol (RHP), in human serum was developed by means of high-performance liquid chromatography (HPLC) with fluorescence detection. Suzuki coupling reaction with a fluorescent arylboronic acid, 4-(4,5-diphenyl-1H-imidazol-2-yl)phenylboronic acid (DPA), was employed to convert HP and RHP into highly fluorescent compounds. HP and RHP were extracted from human serum by liquid-liquid extraction with a mixture of n-hexane and isoamyl alcohol (99:1, v/v) and subsequently labeled by reaction with DPA. Separation of DPA derivatives of HP and RHP was performed on a silica column with a mixture of acetonitrile and H2O (90:10, v/v) containing triethylamine and acetic acid as a mobile phase. The proposed method allowed sensitive detection of HP and RHP in human serum with a detection limit (at a signal to noise ratio of 3) of 0.22 and 0.20 ng/mL, respectively. The applicability of the method for therapeutic drug monitoring (TDM) was demonstrated by analyzing human serum samples from schizophrenic patients receiving HP.