Rapid and accurate determination of chlorpheniramine maleate, noscapine hydrochloride and guaiphenesin in binary mixtures by derivative spectrophotometry.

Rapid and accurate binary mixture resolution of chlorpheniramine maleate-noscapine hydrochloride and chlorpheniramine maleate-guaiphenesin, was performed. Derivative spectrophotometry, by the zero-crossing measurements, was used due to the drugs closely overlapping absorption spectra. Neither sample pretreatment nor separation were required. Linear calibration graphs of first derivative values at 268.0 and 261.0 nm for chlorpheniramine-maleate-noscapine hydrochloride and at 273.2 and 261.0 nm for chlorpheniramine-guaiphenesin were obtained vs. concentration with negligible intercept on the y-axis. Thus, the derivative spectrophotometry method was applied to the determination of these drugs in binary mixtures obtaining selectivity, accuracy and precision.