Validation of an HPLC method for sildenafil citrate analysis in human plasma samples

A simple, precise, rapid and accurate HPLC method for the determination of sildenafil citrate (SLD) in human plasma has been developed based on previous reports, to offer an alternative way to detect and quantify SLD and also to improve some characteristics of the validation process. Chromatography was carried out on a C18 reversed-phase column, using a mixture of acetonitrile: ammonium acetate (0.3 M pH 6.8) (1:1 v/v) as the mobile phase at a flow of 0.750 mL/min. Diazepam was used as an internal standard (IS) and detection was by UV at 240 nm. Samples were extracted with 200 microl of 0.1 M Na2CO3 and 5 mL of diethyl ether: dichloromethane (60:40). Retention times of SLD and IS were 4.8 and 7.1 min, respectively; total run time was 10 min. The linear range of SLD was found to be 20 - 1000 ng/mL. Limit of quantitation (LOQ) and limit of detection (LOD) were calculated to be 10 and 20 ng/mL, respectively. An improved percentage recovery of analyte is reported, showing a fast and reproducible approach to detect SLD in plasma human sample. The method was validated for its linearity, precision, accuracy, recovery, stability and specificity.