Novel methods for the rapid spectrophotometric determination of dapsone

Rapid, sensitive and simple spectrophotometric methods for the determination of dapsone are described. The first method is based on the formation of violet coloured azo product by the diazotisation of dapsone (DAP) followed by a, coupling reaction with. iminodibenzyl (IDB) in alcohol medium. The second method makes use of N-bromosuccinimide (NBS) and promethazine hydrochloride (PMH) to form a green coloured product with dapsone in hydrochloric acid medium. Absorbances of the resulting violet and green products are measured at 570 nm and 610 nm respectively and are stable for 24 h and 50 min at 27degreesC respectively. Beer's law is obeyed in the concentration range of 0.1-2.5 mug mL(-1) of DAP (for IDB) and 0.5-5.0 mug mL(-1) of DAP (for NBS) at 570nm and 610 nm respectively. The methods are successfully employed for the determination of dapsone in pharmaceutical preparation and common excipients used as additives in pharmaceuticals do not interfere in the proposed methods. The methods offer the advantages of rapidity, sensitivity and simplicity without the need for extraction or heating. Reaction sequences are described for the formation of products in both the methods.