Colorimetric determination of astemizole in bulk and in its pharmaceutical dosage forms using flow injection

A continuous flow spectrophotometric method for determining 0.5-100 micrograms ml-1 of astemizole in pure and in dosage forms is suggested. It depends on forming a pinkish orange product which can be quantified spectrophotometrically at 495 nm. The coloured product was due to the action of N-bromosuccinimide on astemizole in alkaline medium and in the presence of a cetyltrimethylammonium bromide micellar medium. The procedure is automated and solutions can be analysed at a rate of 167 h-1 with a relative error of about 1.25%. The limit of detection is 0.5 microgram ml-1 (approximately 1.09 x 10(-6) M). The method is evaluated by a recovery study and by the analysis of commercial formulations.