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, an d vice versa. For this purpose, mathematical parameters were established fo r generating derivative spectra of analytes. The determination of promazine was made using the first-order derivative (Delta lambda = 10 nm, second po lynomial 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 elaborat ed method was successfully used to determine analytes in commercial promazi ne pharmaceuticals. The obtained results agreed well with those obtained by the HPLC method.