Determination of Felodipine in Bulk Drug and its Dosage Formulations using Bromophenol Blue and Bromothymol Blue as Reagents

Two simple, rapid and inexpensive methods based on visible spectrophotometry have been developed for the determination of felodipine in pure form and in dosage forms with two acidic dyes [Bromophenol Blue (BPB) and Bromothymol Blue (BTB)] as the reagents. The proposed methods were based on the formation of ion-pair color complexes between the drug and the two acidic dyes in an acidic buffer. The ion-pair complexes formed, which has an absorption maximum at 420 and 424nm, and were quantitatively extracted into chloroform. All experimental variables for both the proposed methods were studied and optimized. Statistical analysis of the experimental results indicated that the proposed methods were precise and accurate. Excipients used as additives in pharmaceutical formulations did not interfere in the proposed procedures. The proposed procedures were successfully applied to the determination of the bulk drug and its pharmaceutical formulations.