Simultaneous quantification of promazine hydrochloride and its sulfoxide in pharmaceutical preparations

The use of derivative UV-spectrophotometry is proposed for the simultaneous quantification of promazine hydrochloride in the presence of sulfoxide, and vice versa. For this purpose, mathematical parameters were established for generating derivative spectra of analytes. The determination of promazine was made using the first-order derivative (Delta lambda = 10 nm, second polynomial degree) at 268 nm. The quantification of sulfoxide was achieved by applying third-derivative spectra (Delta lambda = 14 nm, sixth polynomial degree) based on measurements of the amplitude at 342 - 344 nm. An elaborated method was successfully used to determine analytes in commercial promazine pharmaceuticals. The obtained results agreed well with those obtained by the HPLC method.