# A sensitive, aqueous-based spectrofluorimetric approach for the determination of favipiravir in presence of its acid-induced degradation product

## TL;DR

This paper introduces a new, eco-friendly method to accurately measure the antiviral drug favipiravir, even when it degrades.

## Contribution

A novel, aqueous-based, environmentally friendly fluorimetric method for determining favipiravir in the presence of its degradation product.

## Key findings

- The method achieves a linear response for favipiravir concentrations between 5–80 ng/mL.
- Detection and quantification limits are 1.6 ng/mL and 4.8 ng/mL, respectively.
- The method is green and eco-friendly, confirmed by GAPI, AGREE, and RGB12 metrics.

## Abstract

The COVID-19 pandemic has emphasized the critical need for novel therapeutic approaches. Favipiravir (FAV), an antiviral drug primarily used for influenza, has shown promising potential in treating COVID-19 and other RNA viral infections. A precise, reliable, and rapid fluorimetric method was established for the quantification of FAV in pharmaceutical formulations, even in the presence of its acid-induced degradation product. The acid-induced degradation product (ADP) of FAV was prepared through forced degradation, followed by characterization using IR and MS. The method leveraged the intrinsic fluorescence characteristics of FAV, exhibiting a linear response within the concentration range of 5–80 ng/mL at 416.5 nm using the first-order derivative processing. Key methodological parameters were optimized to enhance sensitivity, achieving detection and quantification limits of 1.6 ng/mL and 4.8 ng/mL, respectively. All calibration and fluorimetric measurement steps were performed in distilled water without the use of organic solvents or buffers, making the analytical determination phase entirely aqueous and environmentally benign. This method was effectively applied to FAV in both pure drug and pharmaceutical dosage forms. Compared with previously reported fluorimetric methods, it offers the unique combination of aqueous-based operation, stability-indicating capability, and superior analytical performance. Additionally, its environmental sustainability was evaluated using GAPI, AGREE, and RGB12 metrics, which confirmed its green and eco-friendly attributes.

The online version contains supplementary material available at 10.1186/s13065-026-01724-1.