Spectrophotometric determination of furosemide as its Fe(III) complex in pharmaceutical preparations

Application of ion pair complexes to design novel potentiometric membrane sensors for direct determination of frusemide in pharmaceuticals

Background

Fabrication of two membrane sensors using two acidic indicators among sulphonthalein dyes, namely bromophenol blue (BPB) and bromocresol green (BCG), and their use as indicative electrodes for the quantification of frusemide (FUR) is presented. The ion pair complexes of FUR with BPB or BCG are used to prepare the membranes in THF solvent, PVC matrix and dibutyl phthalate (DBP) as plasticizer and subsequently to fabricate FUR-BPB (Sensor I) and FUR-BCG (Sensor II) sensors.

Results

Sensors I and II are employable to determine 2.4 × 10-5–2.4 × 10-3 mol/L FUR at operative pH of 3.71. The calibration curve between the potentials against the concentration of FUR yielded the slopes of 58.73 ± 1 and 57.66 ± 1 mV/decade, respectively, using Sensors I and II, and this confirmed the Nernstian behaviour. Satisfactory correlation was obtained between the measured potentials and FUR concentration with the proposed sensors, and this was revealed by regression coefficient values of 0.9987 and 0.9980 for Sensors I and II, respectively. The LOD (limit of detection) values were calculated and reported for both the sensors. The experimental parameters were optimised to yield acceptable characteristics of both the sensors in the context of performance. The role of excipients of tablets and interferences were assessed by standard addition protocol. The obtained results confirmed the ineffective role of excipients of tablets and foreign species used as interferents.

Conclusion

The designed sensors were validated to confirm the accurate, precise, robust and rugged functioning in determining FUR. The mean of recovered FUR, close to 100%, revealed the acceptable and effective functioning of the proposed sensors. Excellent results were obtained by FUR tablets’ analysis using both the sensors.

Successive ratio subtraction as a novel manipulation of ratio spectra for quantitative determination of a mixture of furosemide, spironolactone and canrenone

Furosemide and spironolactone are commonly prescribed antihypertensive drugs. Canrenone is the main degradation product and main metabolite of spironolactone. Ratio subtraction and extended ratio subtraction spectrophotometric methods were previously applied for quantitation of only binary mixtures. An extension of the above mentioned methods; successive ratio subtraction, is introduced in the presented work for quantitative determination of ternary mixtures exemplified by furosemide, spironolactone and canrenone. Manipulating the ratio spectra of the ternary mixture allowed their determination at 273.6nm, 285nm and 240nm and in the concentration ranges of (2-16μgmL^-1), (4-32μgmL^-1) and (1-18μgmL^-1) for furosemide, spironolactone and canrenone, respectively. Method specificity was ensured by the application to laboratory prepared mixtures. The introduced method was ensured to be accurate and precise. Validation of the developed method was done with respect to ICH guidelines and its validity was further ensured by the application to the pharmaceutical formulation. Statistical comparison between the obtained results and those obtained from the reported HPLC method was achieved concerning student's t-test and F ratio test where no significant difference was observed.

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-sulphamoylanthranillic acid), which makes use of UV detection, a C18, reversed-phase column, and micellar mobile phases of sodium dodecyl sulphate (SDS) and 1-propanol at pH 3 buffered with phosphate system. The most adequate experimental conditions to handle furosemide solutions in the analytical laboratory are studied. The mixture of furosemide and its degradation products which are formed 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 hydrolytic 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, capsules, injectables and drops). The validity of the procedure was checked by analysing 27 pharmaceuticals commercialised in several countries. The label claim percentages and coefficients of variation were in the 95-102% and 0.05-1.3% ranges, respectively. The results showed that the procedure is suitable for routine analysis of the diuretic.