[Methodological study on the determination of naftopidil concentration in biological samples by HPLC]

A method was developed for the determination of the novel antihypertensive drug naftopidil in biological samples by HPLC. Metoprolol was used as the internal standard. The analytical column was a stainless steel column filled with 10 micron C18 packing. The mobile phase was a mixture of methanol-acetonitrile-water-0.2 mol.L-1 HAc-0.2 mol.L-1 NaAc (50:45:5:0.9:0.1). Detection was performed at UV 232 nm. Biological samples can be well purified after two extractions with ether. The lowest detection limit was 5 ng.ml-1. The precision and accuracy within-day and day-to-day ranged from 3.17 to 10.88%. The mean recoveries were 79.35% to 95.72%. The results showed that this method was simple, sensitive and good enough to be used in pharmacokinetic study of naftopidil.