Determination of some sulphonamides by sequential injection analysis with chemiluminescence detection

Determination of a group of sulphonamides (sulphanilamide, sulphacetamide, sulphathiazole, sulphadimidine, sulphafurazole, sulphamethoxypyridazine, sulphaguanidine) using sequential injection analysis (SIA) technique with chemiluminescence (CL) detection has been devised. The CL signal was emitted during the oxidation of sulphonamides by potassium permanganate in sulphuric acid medium. The lab-made SIA system consisted of a 2.5ml Cavro syringe pump, eight-port Vici Valco selection valve and a lab-modified Spectra-Physics FS 970 fluorescence detector. It was controlled by a PC with use of originally compiled LabVIEW®supported software. Concentration, volume of reagents and flow rate were optimised by a simplex method. A number of enhancers was tested to increase the CL signal. The optimum conditions and sequence of injected zones for sulphanilamide (model substance) were: 0.1M glutaraldehyde 45?l, sample 50?l; 0.5M H2SO4 45?l; 1mM KMnO4 46?l and 100?ls-1 flow rate. The transient CL signal (lambda=" border=0 src="/.dejavu/.tact/lib1/art410/pcdata/html_gif/charset.gif/bmd.gif"390nm) was recorded after a single reversal of the flow. Calibration curves relating the intensity of CL (peak heights) to the concentration of the analytes were curvilinear (of the second polynomial order) with rectilinear sections typically in the range ~0.01-0.5mM sulphonamide. The sample throughput was 120h-1. The proposed method has been applied for the assay of sulphacetamide and sulphafurazole in pharmaceutical dosage forms. The SIA results did not show any statistically significant difference from those obtained by titrimetry according to USP XXIV.