Spectrophotometric Determination of Furosemide in Pharmaceuticals Using Permanganate

Abstract

Based on the reduction of permanganate by furosemide (FUR) in either acidic or basic
medium, two simple, sensitive and cost-effective methods were proposed for the determination
of FUR in bulk drug and in formulations. In method A, FUR was treated with a measured excess
of permanganate in acid medium and the unreacted oxidant was measured at 550 nm, whereas
in method B the reaction was carried out in alkaline medium and the resulting manganate was
measured at 610 nm. In method A, the amount of permanganate reacted corresponds to the
FUR content and the absorbance was found to decrease linearly with the concentration; while in
method B, the absorbance increases with concentration. Under optimum conditions, working
ranges was 3.0-24.0 µg ml
-1
and 1.25-20.0 µg ml
-1
by method A and method B, respectively. The
calculated molar absorptivities are 9.06 × 10
3
and 1.36 × 10
4
L mol
-1
cm
-1
for method A and
method B, respectively, with corresponding Sandell sensitivity values of 0.0365 and 0.0243 µg
cm
-2
. The limits of detection (LOD) and quantification (LOQ) have also been reported. Accuracy
and precision for the assay were determined by calculating the intra-day and inter-day at three
concentration levels; the intra-day RSD was < 2.7% and the accuracy was better than 2.8%
(RE). The methods were successfully applied to the determination of FUR in tablets and
injections dosage forms; either in monopreparations of FUR or in combination with amiloride
HCl. The results tallied well with the label claim and were statistically compared with those of a
reference method by applying the Student’s t-test and F-test. The accuracy was further
ascertained from placebo and synthetic mixture analysis and also from spike-recovery method.