Label‐Free Spectrofluorometric Method for Simultaneous Estimation of Methocarbamol and Aspirin in Biological and Pharmaceutical Matrices: Whiteness and Greenness Evaluation

A combination of methocarbamol and aspirin is commonly used for the treatment of acute musculoskeletal pain, such as low back and neck pain. Simultaneous analysis of these analytes in dosage forms and biofluids using rapid, sensitive, and selective methods would be highly beneficial. Herein, we report the first direct, label-free spectrofluorometric method for simultaneously quantifying methocarbamol (MET) and aspirin (ASP) in coformulated tablets and spiked human urine. The method utilizes excitation at 274 nm with independent emission detection at 300 nm for MET and 402 nm for ASP, using methanol as the diluting solvent. The assay was rectilinear over ranges of 0.10-0.80 μg/mL for MET and 0.05-0.50 μg/mL for ASP with detection limits of 14.9 and 10.6 ng/mL for MET and ASP, respectively. The method was validated in compliance with ICH regulations. The approach was applied efficiently to assay both analytes in their tablets and spiked human urine with high % recoveries (98%-103%) and low RSD (1.7%-3.3%). In addition, the sustainability and practicality of the developed method were assessed using the RGB-12 whiteness algorithm, indicating the whiteness of the developed method. The method's greenness was also confirmed using three greenness metrics that showed excellent eco-friendliness of the developed method.