One titrimetric and two spectrophotometric methods are described for the determination of ketotifen fumarate (KTF) in bulk drugand in tablets using cerium(IV) as the oxidimetric agent. In titrimetry (method A), the drug was treated with a measured excess of cerium(IV) in H2SO4 medium and after a standing time of 10 min, the surplus oxidant was determined by back titration with iron(II). The spectrophotometric procedures involve addition of a known excess of cerium(IV) to KTF in acidmedium followed by the determination of unreacted oxidant by reacting with either p-dimethyl amino benzaldehyde and measuring the resulting colourat 460 nm(method B) or o-dianisidine and subsequent measurement of the absorbance of coloured product at 470nm (method C).Titrimetric assay is based on a 1 : 2 reaction stoichiometry between KTF and cerium(IV) and the method is applicable over 2–18mgrange. In spectrophotometry, regression analysis of Beer’s law plots showed a good correlation in 0.4–8.0 and 0.4–10.0 gm L−1KTF ranges for method B and method C, respectively, and the corresponding molar absorptivity coefficients are calculated to be 4.0×104and 3.7 × 104 Lmol−1 cm−1.
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