Experimental design approach for development of spectrofluorimetric method for determination of favipiravir; a potential therapeutic agent against COVID-19 virus: Application to spiked human plasma

Abstract

The present work describes development of rapid, robust, sensitive and green spectrofluorimetric method for determination of favipiravir (FAV). Different factors affecting fluorescence were carefully studied and Box Behnken Design was applied to optimize experimental parameters. The proposed method is based on measuring native fluorescence of FAV in 0.2 M borate buffer (pH 8.0) at 432 nm after excitation at 361 nm. There was a linear relationship between FAV concentration and relative fluorescence intensity over the range 40-280 ng/mL with limit of detection of 9.44 ng/mL and quantitation limit of 28.60 ng/mL. The method was successfully implemented for determination of FAV in its pharmaceutical formulation with mean % recovery of 99.26 ± 0.87. Moreover, the high sensitivity of the method allowed determination of FAV in spiked human plasma over a range of 48-192 ng/mL. The proposed spectrofluorimetric method was proved to be eco-friendly according to analytical eco-scale.

Keywords: COVID-19 virus; Experimental design; Favipiravir; Human plasma; Pharmaceutical analysis.

Graphical abstract

Fig. 1

Chemical structure of favipiravir (FAV).

Fig. 2

Excitation and emission spectra of 120 ng/mL FAV, where (A) is the excitation of FAV, (A’) is the emission of FAV, (B) is blank excitation and (B’) is blank emission.

Fig. 3

(a) Effect of different solvents on RFI of FAV, (b) Effect of different buffers on RFI, and (c) Effect of different surfactants on RFI of FAV.

Fig. 4

Box Behnken Design Results (a) contour plot, (b) 3D response surface plot, (c) interaction plot and (d) Desirability plot.