SPECTROPHOTOMETRIC DETERMINATION OF DRUGS IN PHARMACEUTICAL FORMULATIONS WITH N-BROMOSUCCINIMIDE AND CELESTINE BLUE

Simple, sensitive and selective methods are proposed for the spectroph otometric determination of drugs, viz., tetracycline HCl, nifurtimox, ethionamide, propranolol HCl and isonicotinic acid hydrazide, based on their reactivity with N-bromosuccinimide (NBS). The method involves t he addition of excess NBS of known concentration in the presence of 0. 25 M HCl and the unreacted NBS is determined by the measurement of the decrease in the absorbance of the dye celestine blue (lambda(max) 540 nm), which was found to be the most suitable of several dyes tested. This method was applied for the determination of drug contents in phar amaceutical formulations and enabled the determination of the drugs in microgram quantities (0.2 to 5 mu g/ml). Standard deviations were typ ically less than or equal to 0.5 mg per dose (RSD 0.1-1.0%). No interf erences were observed from excipients and the validity of the method w as tested against reference method. Recoveries were 99.8-101.1%.