Spectrofluorimetric methods for the determination of mirabegron by quenching tyrosine and L-tryptophan fluorophores: Recognition of quenching mechanism by stern volmer relationship, evaluation of binding constants and binding sites.

Green spectrofluorimetric methods have been adopted for the determination of Mirabegron (MG) in pure drug and pharmaceutical dosage form. The developed methods based on fluorescence quenching of tyrosine and L-tryptophan amino acids fluorophores by the effect of Mirabegron as a quencher. Experimental conditions of the reaction were studied and optimized. The Fluorescence quenching (ΔF) values were proportional to the concentration range of MG 2-20 µg/ml for the tyrosine-MG system in buffered media pH 2 and 1-30 µg/ml for L-tryptophan-MG system pH 6. Good correlation coefficients with low detection limits of 0.163 and 0.234 µg/ml for the two systems respectively. Method validation was applied according to ICH guidelines. The cited methods were successively applied for MG determination in tablet formulation. No statistically significant difference between the results of the cited and the reference methods regarding t and F tests. The proposed spectrofluorimetric methods are simple, rapid, eco-friendly and can contribute to MG's methodologies in quality control labs. Stern-Volmer relationship, the effect of temperature, quenching constant (Kq), and UV spectra were studied to identify the mechanism by which the quenching might occur. The results demonstrated that fluorescence quenching of tyrosine was a dynamic quenching process and L-tryptophan was static. The double log plots were constructed to determine the binding constants and binding sites. The greenness profile of the developed methods has been assessed by Green Analytical procedure index (GAPI) and Analytical Greenness Metric Approach (AGREE).

Validated spectrofluorimetric methods for the determination of apixaban and tirofiban hydrochloride in pharmaceutical formulations.

Apixaban and Tirofiban Hydrochloride are low molecular weight anticoagulants. The two drugs exhibit native fluorescence that allow the development of simple and valid spectrofluorimetric methods for the determination of Apixaban at λ ex/λ em=284/450nm and tirofiban HCl at λ ex/λ em=227/300nm in aqueous media. Different experimental parameters affecting fluorescence intensities were carefully studied and optimized. The fluorescence intensity-concentration plots were linear over the ranges of 0.2-6µgml-1 for apixaban and 0.2-5µgml-1 for tirofiban HCl. The limits of detection were 0.017 and 0.019µgml-1 and quantification limits were 0.057 and 0.066µgml-1 for apixaban and tirofiban HCl, respectively. The fluorescence quantum yield of apixaban and tirofiban were calculated with values of 0.43 and 0.49. Method validation was evaluated for linearity, specificity, accuracy, precision and robustness as per ICH guidelines. The proposed spectrofluorimetric methods were successfully applied for the determination of apixaban in Eliquis tablets and tirofiban HCl in Aggrastat intravenous infusion. Tolerance ratio was tested to study the effect of foreign interferences from dosage forms excipients. Using Student's t and F tests, revealed no statistically difference between the developed spectrofluorimetric methods and the comparison methods regarding the accuracy and precision, so can be contributed to the analysis of apixaban and tirofiban HCl in QC laboratories as an alternative method.