Application of promethazine hydrochloride as a chromogenic reagent for the spectrophotometric determination of certain sulphonamide drugs

Abstract

The oxidative coupling reaction of promethazine · HCl with primary aromatic amines was applied to the determination of seven pharmaceutical sulphonamides. A mixture of an acidic solution (3.5% acetic acid) of the sulphonamide and the chromogenic reagent was treated with hypochloriteion. The wavelength of maximum absorption is 610 nm, the molar absorptivities range from 1.57×104 to 1.89×104 l mole−1 cm−1 and Sandell sensitivities range from 0.00972 to 0.0136 μg cm−2. A linear correlation was found between absorbance at λmax and concentration. The procedures developed for bulk sulpha drugs and some of their pharmaceutical preparations are rapid, accurate, precise and comparable to the Bratton-Marshall procedure.