Spectrophotometric Determination of Some Sulphonamide Drugs via oxidative coupling with Phenothiazine and Benzoyl peroxide using flowinjection technique

Abstract

A novel flow injection Spectrophotometric method is described for the determination of
microgram amounts of sulphonamides in aqueous and biological samples. The method is
based on the oxidative coupling reaction of phenothiazine with sulphonamide drugs in the
presence of benzoyl peroxide as oxidising agent. Intense bluish-green, water soluble stable
dye was obtained which has a maximum absorption at 614 nm. Linear calibration graphs were
obtained for different sulphonamides with a molar absorptivities of 3250-4720 1. mol'' cm "
and a relative standard deviation of better than 0.84 %. The proposed method has proved to be
highly sensitive (detection limit range 0.30-0.63 p g ml-1 sulphonamide) and accurate
(recovery % was 97.9-100.2 %)).
Optimum concentrations of chemical reactants, physical instrumental conditions and effects
of interferences from certain additives have been investigated. The nature of the coloured
produced dye and its stability constant were determined. The method was applied successfully
for the determination of sulphonamide drugs in pharmaceutical preparations, blood and urine
samples.