Spectrophotometric and High Performance Liquid Chromatographic Methods for the Determination of Dapsone in a Pharmaceutical Preparation

The detailed investigation of a sensitive and selective spectrophotometric method for the determination of dapsone; based on the oxidative coupling reaction of dapsone drug with pyrocatechol in the presence of potassium periodate in acidic medium to form an intense, stable, purple-red coloured water-soluble dye, which shows a maximum absorption at 509 nm. Beer's law obeyed over the range of 10-500 g /25 ml, i.e,0.4-20 ppm with a molar absorptivity of 1.05104l.mol-1.cm-1and Sandell's sensitivity index of 0.0235 g.cm-2,a relative standard deviation of 2.60 to 1.05%; and limit of detection, (LOD) of 0.1735 g.ml-1.; and (LOQ) of 0.5785g.ml-1. And the method does not require temperature control or solvent extraction. HPLC technique has been also developed for the measurement of dapsone. The analysis was achieved on a C18 column using water and acetonitrile in the ratio of 50:50 (V:V) as a mobile phase at a flow rate equals to 0.5 ml / min. and the detection was done spectrophotometrically at 297 nm. A linear relationship is obeyed over the range 0.5-20 ppm with a relative standard deviation (RSD) 1.53 to 0.83% and relative error -0.3 to +1.1 %. Both methods were applied successfully to the assay of dapsone in pharmaceutical preparation (Tablet).