Incorporation of eggshell waste in the preparation of carbon quantum dot nanoprobes for the determination of COVID-19 antiviral drug; molnupiravir

Abstract

New carbon quantum dots (CQDs) with multi-doped elements from eggshell biomass waste have been employed as a direct, fast, green, and selective probe for the fluorometric determination of molnupiravir, a COVID-19 antiviral drug. For the first time, the eggshell@CQDs were prepared through a simple, single-step microwave heating process that only took 90 s. Upon excitation at λex 340 nm, the resulting CQDs exhibited a maximum bluish fluorescence emission at λem 408 nm. Molnupiravir was found to quench the native fluorescence of the prepared CQDs in a quantitative manner, based on a static mechanism by forming a non-emissive complex. The spectrofluorometric method designed for molnupiravir detection was validated per the International Council for Harmonization (ICH) requirements. The proposed fluorescent probe showed good linearity for molnupiravir detection over a range of 2.5–70 µg/mL, with percent recoveries ranging from 99.53 % to 101.79 % and %RSD (relative standard deviation) less than 1 %. The eggshell@CQDs were successfully employed to determine molnupiravir levels in marketed hard capsules, yielding good percent recoveries and repeatability. The developed approach was found to be greener than the published HPLC/UV approach, as assessed by the analytical eco-scale, green analytical procedure index (GAPI), and analytical greenness metric approach (AGREE). Furthermore, this approach highlights the potential of synthesizing CQDs from natural biomass, specifically low-value biomass waste such as eggshells.