Spectrophotometric determination of astemizole

Four simple and sensitive spectrophotometric methods for the determination of astemizole (AZ) in pure samples and pharmaceutical formulations are described. They are based on the oxidation of astemizole with excess N-bormosuccinimide (NBS) and determination of the unconsumed NBS with, metol-sulphanilamide (method A, lambda(max): 520 nm) or celestine blue (method B, lambda(max): 540 nm); or by the reduction of Folin-ciocalteu reagent (method C, lambda(max): 720 nm); or by the formation of a chloroform-soluble, coloured ion-association complex between the drug and azocarmine G (AG) at pH 1.5 (method D, lambda(max); 540 nm). The results obtained are reproducible with a coefficient of variation of less than 1.0%.