New simple, rapid, and accurate spectrophotometric techniques for sulphanilamides assay in combination drugs have been elaborated. The method is based on the formation of coloured products of sulphanilamides diazonium salt azoсoupling with heterocyclic azo reagent 4-(2-thiazolylazo)-resorcinol (TAR) in alkaline medium (pH 9.5) with the following measurement of their absorbance at λmax = 615 nm. Formed products are stable for 1 hour at room temperature. Effective molar absorptivities at absorbance maximum 615 nm for disazo dyes were ~ 104 M-1 cm-1. Linear ranges for sulphanilamides determination were 0.5−30.0 μg mL-1. The developed method was used for the suphanilamides determination in tablets, powder, solutions, suspensions and ointments.
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