Furosemide assay in pharmaceuticals by Micellar liquid chromatography: study of the stability of the drug

A simplified high-performance liquid chromatographic procedure is described for the determination of furosemide (4-chloro-N-furfuryl-5-sulphamoylanthr anillic acid), which makes use of UV detection, a C-18 reversed-phase colum n, and micellar mobile phases of sodium dodecyl sulphate (SDS) and 1-propan ol at pH 3 buffered with phosphate system. The most adequate experimental c onditions to handle furosemide solutions in the analytical laboratory are s tudied. The mixture of furosemide and its degradation products which are fo rmed upon light exposition was resolved with a mobile phase of 0.04 M SDS-2 % propanol. Separation of furosemide from its common impurities and the hyd rolytic product, 4-chloro-5-sulphamoylanthranillic acid, was also possible. A mobile phase of larger elution strength, such as 0.06 M SDS-8% propanol was preferred to assay furosemide in several dosage forms (tablets, capsule s, injectables and drops). The validity of the procedure was checked by ana lysing 27 pharmaceuticals commercialised in several countries. The label cl aim percentages and coefficients of variation were in the 95-102% and 0.05- 1.3% ranges, respectively. The results showed that the procedure is suitabl e for routine analysis of the diuretic. (C) 2000 Elsevier Science B.V. All rights reserved.