CONTINUOUS-FLOW SPECTROPHOTOMETRIC DETERMINATION OF SULFADIAZINE BY DIAZOTIZATION WITH IN-SITU PREPARATION OF NITRITE

Nitrite is prepared in situ for the determination of sulfadiazine. The method is based on solid-phase reduction of copperized cadmium of nit rate; the nitrite reagent merges with the sample stream in hydrochlori c acid medium and the resulting mixture is injected into the water car rier, pure distilled water, and then merges with the N-(1-naphthyl)eth ylendiamine reagent and is measured spectrophotometrically at 542.0 nm . The calibration graph is linear over the range 0.5-50 mu g ml(-1) su lfadiazine, mid-range R.S.D.=0.3% (n = 5) and sample throughput 72 h(- 1). The procedure is applied to sulfadiazine determination in a pharma ceutical formulation and to in vitro dissolution studies of two differ ent pharmaceutical formulations. The method makes the frequent prepara tion of the unstable nitrite solution unnecessary; the physical and ch emical characteristics as well as the life-span of the solid-phase rea ctor are also studied.