A Validated Spectrophotometric Method for Determination of Formoterol Fumarate Dihydrate in Bulk and Dosage Form Using Methyl Orange As Ion Pair Reagent

In this study rapid, simple, accurate and sensitive spectrophotometric method has been developed for the determination of formoterol fumarate dihydrate in bulk and dosage forms. The method is based on the formation of yellow coloured ion pair complex due to the reaction of formoterol fumarate dihydrate (FF) and methyl orange (MO) at pH 4. Ion pair complex has a maximum absorption at 428 nm in chloroform and a linear calibration over the range of 4-20 mu g/mL. The slope of the calibration curve was 0.0433, limit of detection was 0.22 mu g/mL and limit of quantification was 0.66 mu g/mL. The proposed method has been applied to the assay of formoterol fumarate dihydrate commercially available capsules. There was no significiant difference between the results obtained by proposed and reference methods in view of accuracy and reproducibility. No interference was observed from common excipients.