Spectrofluorometric Determination of Tiotropium Bromide by Ion Pair Extraction Using 9, 10 Dimethoxyanthracene-2-sulphonate Sodium

Abstract

A rapid, simple and specific fluorometric procedure is described for the analysis of the anticholinergic drug, tiotropium bromide (TIO) in bulk and in capsule formulation. The method is sensitive and is based on the reaction of this drug as a quaternary ammonium compound with the fluorogenic reagent 9, 10-dimethoxyanthracene-2-sulphonate (DMOAS) as counter ion in acidic medium and the proposal of the reaction pathway was postulated. The hydrophobic ion-pair formed was extracted in dichloroethane and measured spectrofluorometrically at 450 nm after excitation at 385 nm. The fluorescence intensity-concentration plot was rectilinear over the ranges of 7-30 ng m1-1 y=mx+b, r2=0, 9991 (m =12.054; b =156.27).The detection limit was 0.0326 ng ml-1 based upon United States Pharmacopeia (USP 2002). The different parameters affecting the reaction pathway were studied and optimized. The proposed method was successfully applied to the analysis of tiotropium capsules. No interference was observed from pharmaceutical excepients such as lactose.