Colorimetric determination of ethambutol hydrochloride

A precise colorimetric procedure is proposed for estimation of ethambutol hydrochloride, based on reaction of the drug with 2,4-dinitro-1-fluorobenzene under stipulated conditions. The yellow chromophore is quantitated spectrophotometrically at 376 +/- 1 nm. The relationship between absorbance and drug concentration was linear within a range of 5-40 micrograms/mL. The method is suitable for the analytical control of ethambutol HCl and its formulations.