Determination of donepezil hydrochloride in human plasma and pharmaceutical formulations by HPLC with fluorescence detection

A sensitive, isocratic reversed-phase high performance liquid chromatographic method involving fluorescence detection was developed for the determination of donepezil hydrochloride in tablets and in human plasma. Pindolol was used as an internal standard. Good chromatographic separation was achieved by using an analytical column C18. The system operated at room temperature using a mobile phase consisting of methanol, phosphate buffer (0.02 mol L^-1) and triethyl amine (pH 3.5) (55: 45: 0.5, V/V/V) at a flow rate 0.9 mL^-1 min. The analyte and internal standard were extracted from human plasma via liquid-liquid extraction. The proposed method was validated for sensitivity, selectivity, linearity, accuracy and precision. The calibration curve was linear over the range of 5-2000 ng mL^-1 of donepezil with detection limit of 1.5 ng mL^-1. Intra- and inter-day relative standard deviations were less than 2.5 %. The method was found to be suitable for quality control of donepezil hydrochloride in bulk drug as well as in human plasma.