Validation and Stability Indicating RP-HPLC Method for the Determination of Sildenafil Citrate in Pharmaceutical Formulations and Human Plasma

A simple, selective, accurate reverse phase-high performance liquid chromatographic (RP-HPLC) method was developed and validated for the analysis of sildenafil citrate in pharmaceutical formulations. Chromatographic separation achieved isocratically on a C18 column (Use Inertsil C18, 5μ , 150 mm x 4.6 mm) utilizing a mobile phase of acetonitrile/phosphate buffer (70:30, v/v, pH 7.0) at a flow rate of 0.8 mL/m with UV detection at 228 nm. The retention time was 4.087. The method is accurate (99.15-101.85%), precise (intra-day variation 0.13-1.56% and inter-day variation 0.30-1.60%) and linear within range 0.1-30 μg/mL (R2=0.999) concentration and was successfully used in monitoring left over drug. The detection limit of sildenafil citrate at a signal-to-noise ratio of 3 was 1.80 ng/mL in human plasma while quantification limit in human serum was 5.60 ng/mL. The proposed method is applicable to stability studies and routine analysis of sildenafil citrate in pharmaceutical formulations as well as in human plasma samples.