6533b7d7fe1ef96bd12682af

RESEARCH PRODUCT

Enhanced flow-injection–chemiluminometric determination of sulphonamides by on-line photochemical reaction

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Abstract The viability of the tandem photochemical reaction-chemiluminescence detection has been studied for an heterogeneous group of sulphonamides (sulphamethoxazole, sulphadiazine, sulphamerazine, sulphamethoxypyridazine, sulphacetamide, sulphadimidine, sulphanilamide, sulphathiazole and sulphaguanidine) using sulphamethoxazole (whose chemiluminescent behaviour has not been previously reported) as a test substance. The ‘on-line’ photochemical-reaction of sulphonamides provides an enhancing influence on the chemiluminometric response of the drugs during their oxidation by potassium permanganate in sulphuric acid medium (sulphamethoxazole, sulphacetamide, sulphadimidine and sulphanilamide increase their chemiluminometric response by a factor≥10). The determination is performed in a FI-assembly by using a photoreactor consisting of a 670 cm×0.5 mm i.d. long piece of PTFE tubing coiled around a 8 W low-pressure mercury lamp. Linear calibration graphs were obtained over a concentration range of 2–3 orders of magnitude, typically in the range ≈0.06–8 μg ml−1 (sulphamethoxazole, sulphacetamide, sulphadimidine, sulphanilamide, sulphathiazole, sulphaguanidine); and in the range ≈0.08–100 μg ml−1 (sulphadiazine, sulphamerazine and sulphamethoxypyridazine). Limits of detection were between 30 μg l−1 (for sulphanilamide) and 80 μg l−1 (for sulphadiazine, sulphamethoxypyridazine, sulphadimidine and sulphaguanidine). The sample throughput was 60 h−1 in all cases. The assessment of the photodegradation step on the molecular structure of sulfonamides was established by recording UV and fluorimetric spectra. The viability of an on-line photochemical reaction-fluorimetric determination of sulphathiazole and sulphadimidine was confirmed. The method was also applied to the determination of dissolution profiles of commercially available formulations of solid oral administration of sulfamethoxazole. The empirical profiles were adjusted by regression using the three-parameters plot method.