Abstract
A flow injection spectrophotometric method based on furosemide reaction with potassium permanganate is described. A flow system using as carrier a 3.0 x 10-4 mol/l potassium permanganate solution was developed. This system used a 50 cm sample loop and a 100 cm reactor, which was kept at 50°C. The permanganate flow rate was 2.2 ml min-1. The analytical signal was the bleaching of the carrier solution, caused by the reaction between furosemide and potassium permanganate. The detection at 550 nm presented a linear range from 1.0 to 6.0 x 10-4 mol/l, with a calibration equation equals to y = 587.5x + 0.09 (in which r = 0.995, n = 6), the limit of detection (3σ/slope) was 1.1 x 10-5 mol/l. The proposed method was applied to commercial samples from three different brands, as tablets and ampoules. It presented an adequate analytical frequency (40 measurements per hour), with results according to the labeled values.
