Development and validation of novel analytical methods for estimation of doxofylline in bulk and dosage forms

Three simple, sensitive and accurate spectrophotometric methods (A, B and C) were developed to determine doxofylline in bulk and in its dosage forms. Method A is based on charge-transfer complex formation of the drug with p-chloranilic acid. Method B involves the formation of colored chloroform extractable ion-pair complex of the drug with bromophenol blue under acidic condition. Method C is based on ternary complex formation of the drug with molybdenum(V) thiocyanate binary complex. The colored products are quantitated spectrophotometrically at 540, 390 and 690 nm by methods A, B and C, respectively. The variables, which affected the reactions were carefully studied and optimized. The linear ranges for the proposed methods were 4-32 μg/mL (method A & B) and 2-16 μg/mL (method C). Analytical performance of the methods was statistically validated. The proposed methods were successfully applied to the analysis of doxofylline in its dosage forms and were found to be comparable with that of reference method.