Development of RP-HPLC, HPTLC and UV-Visible Spectrophotometry Methods

Six methods RP-HPLC, RP-HPTLC/densitometry and UV-Spectrophotometry (first order amplitude, first order AUC, second-order amplitude and second order AUC) have been developed for the determination of tadalafil in bulk and pharmaceutical formulation. RP-HPLC and RP-HPTLC/Densitometry methods are found to be accurate, precise, rugged and robust. Both these methods are adequately sensitive. The only limitation of RP-HPLC and RP-HPTLC/densitometry method is their cost. For RP-HPLC study, Design Expert software ver. 8.0.4 was used to study robustness parameter, which showed that method is robust. From results of ANOVA and analysis of response surfaces plots; it can be concluded that responses, y1 (Retention time) and y2 (Tailing factor) are robust for x1, x2, and x3; however, for y3(Theoretical plates) x1, x2, and x3 affect considerably. All four UV-Spectrophotometric methods are simple, accurate, precise and least calculations are involved for estimation of concentrations of the drug. No interference of the excipients was observed in any one of the methods during tablet assay. All the developed methods can be used for routine analysis of tadalafil in the pharmaceutical formulation.