Ultrasensitive First Derivative Synchronous Spectrofluorimetric Approach for the Concurrent Quantification of COVID-19-2024 Treatment Combination Dextromethorphan and Guaifenesin in Different Matrices: Compliance With Greenness and Practicality Metrics

The COVID-19-2024 is one of the most frequently occurring illnesses worldwide. One of the symptoms of COVID-19 is sever cough. This study presents a novel first derivative synchronous spectrofluorimetric method that is rapid, highly sensitive, cost-effective, and environmentally safe for determining two coformulated anticough drugs, dextromethorphan and guaifenesin, simultaneously. At 281.5 and 297.4 nm, respectively, the fluorescence of guaifenesin and dextromethorphan was measured. The dilution solvent was methanol, and the wavelength difference (Δλ) was 20 nm. The method verified good linearity (r > 0.999) for both dextromethorphan (10.0–200.0 ng mL⁻¹) and guaifenesin (30.0–800.0 ng mL⁻¹) within the intended concentration ranges. The findings showed that the suggested method had a high degree of sensitivity, with detection limits for guaifenesin and dextromethorphan being 8.64 and 1.81 ng mL⁻¹, respectively. For both analytes, the intraday and interday precisions were less than 0.81% RSD. With low percentage RSD values and high percentage recoveries, the developed method was successfully used to estimate the aforementioned medications in dosage forms and human plasma samples simultaneously. The CACI tool evaluated the method's economy, usefulness, and applicability, whereas MoGAPI and AGREE metrics verified its exceptional eco-friendliness and greenness. The procedure was thoroughly verified in compliance with ICH Q2 (R2) standards.