Determination of some sulphonamides by sequential injection analysis with chemiluminescence detection Original Research Article

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 2.5 ml 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: 0.1 M glutaraldehyde 45 μl, sample 50 μl; 0.5 M H2SO4 45 μl; 1 mM KMnO4 46 μl and 100 μl s−1 flow rate. The transient CL signal (λ≥390 nm) 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 ≈0.01–0.5 mM sulphonamide. The sample throughput was 120 h−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.