A Dual-Mode Spectrophotometric and Fluorescent Probe Based on Lignin-Derived Carbon Dots for the Detection of Atorvastatin Calcium in a Bulk Powder and a Commercial Product

Recently, dual-mode techniques have garnered considerable attention and have been shown to be effective approaches for biomedical analysis and environmental monitoring. A novel and simple dual-mode spectrophotometric and fluorometric probe based on lignin-derived carbon dots (LCDs) was developed to detect atorvastatin calcium (ATS) in a bulk powder and its commercial product. The synthesized LCDs exhibit exceptional fluorescence characteristics and are highly soluble in water while maintaining reasonable stability. The average particle size of the LCDs was 3.42 ± 1.03 nm. The characterization of the produced LCDs indicated a structure resembling graphene oxide with the presence of several functional groups. The developed LCDs show a good fluorescence quantum yield of 32.2%. The fluorescence of the LCDs is quenched by ATS at an emission wavelength of 315 nm after excitation at 275 nm through dynamic and static quenching mechanisms. The optimal reaction conditions for the dual-mode reaction were a pH of 9 and 0.05 mL of the LCDs, which were measured after 3 min at 30 °C by spectrophotometry, followed by 7 min at 20 °C by fluorometric methods. According to the spectrophotometric results, the response of ATS was linear in the range of 4.0-100.0 µg/mL, while according to the fluorometric results, the dynamic range was 3.0-50.0 µg/mL. The limits of detection (LODs) and the limits of quantification (LOQs) were 0.97 µg/mL and 2.95 µg/mL for the fluorometric method, respectively. The nanoprobe effectively analyzed ATS in medication samples and yielded good results.