Novel coupling reagents for the sensitive spectrophotometric determination of nimesulide in pharmaceutical...

Novel coupling reagents are used for the sensitive spectrophotometric determination of nimesulide (NIME) in either pure form or in its pharmaceutical preparations. The methods are based on the diazotisation of reduced NIME, followed by either coupling with alcoholic iminodibenzyl (IDB) in acid medium to give a deep blue coloured product (lambda(max) of 600 nm) or coupling with 3-aminophenol (AP) in acid medium to produce an orange red coloured product (lambda(max) of 470 nm). Both the methods are highly reproducible and have been applied to a wide variety of pharmaceutical preparations and the results compare favourably with the reported method. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed methods.