COLORIMETRIC METHOD FOR THE SIMULTANEOUS DETERMINATION OF CHLORPHENOXAMINE HYDROCHLORIDE AND ANHYDROUS CAFFEINE IN PURE AND DOSAGE FORMS WITH ROSE-BENGAL

A rapid, simple and sensitive colorimetric method for the simultaneous determination of chlorphenoxamine HCl and anhydrous caffeine was deve loped, based on charge-transfer complex formation of the drugs with ro se bengal in basic media of pH 9.0. The chlorphenoxamine HCl (I) compl ex was measured at 588 nm whereas anhydrous caffeine (II) was measured at 551 nm. The optimal experimental parameters for colour production were studied. Beer's law was obeyed in the concentration ranges 2-40 a nd 2-34 mu g ml(-1) for I and II, respectively. The Ringbom optimum co ncentration ranges were 3-36 and 3-30 mu g ml(-1) for I and II, respec tively. The results obtained showed good recoveries of 100.2 +/- 1.5 a nd 99.7 +/- 1.3% with relative standard deviations of 0.37 and 0.47% f or I and II, respectively. Applications of the method to representativ e pharmaceutical dosage forms are presented and the validity assessed by applying the standard addition technique.