Sensitive spectrophotometric determination of vardenafil HCl in pure and dosage forms

The present work aims to develop and validate a simple, rapid, cost-effective, sensitive and extractive spectrophotometric methods for the determination of phosphodiesterase type 5-inhibitor; vardenafil HCl (VARD) in pure and in dosage forms.

The developed methods are based on the formation of ion-pair complexes between vardenafil HCl and dyes, namely, bromocresol green (BCG), bromocresol purple (BCP), bromophenol blue (BPB), bromothymol blue (BTB) and eriochrom black T (EBT) in acidic buffer solutions. Different factors affecting the reactions between VARD and the dyes were studied and optimized.

The formed complexes were extracted with methylene chloride and measured at 418, 410, 415, 417 and 520nm using BCG, BCP, BPB, BTB and EBT, respectively. The beer's law was obeyed in the ranges 1.0-10, 1.0-16, 0.5-8.0, 2.0-20 and 1.0-14μgmL^-1 for BCG, BCP, BPB, BTB and EBT, respectively under the optimum conditions. The composition of the ion-pairs was found 1:1. The molar absorptivity's, Sandell's sensitivity, limits of detection and the limits of quantification were calculated. Other method validation parameters, such as accuracy, intra-day and inter-day precision, robustness, ruggedness and selectivity, have been evaluated.

The proposed methods have been applied successfully for the analysis of vardenafil HCl in pure and dosage forms. The reliability of the methods was further ascertained by performing recovery studies using the standard addition method. Statistical comparison of the results with the reported method was performed by applying student's t- and F-tests and no significant statistical differences were obtained.