Simultaneous spectroscopic analysis of methocarbamol with its impurity guaifenesin: assessment of greenness, blueness and whiteness applying different sustainability tools

This work introduces an eco-friendly spectrophotometric approach for the simultaneous quantification of methocarbamol (MET) and its impurity product guaifenesin (GUF), based on measuring the second derivative amplitudes of each drug in presence of the other, using zero-crossing technique. The second derivative amplitudes were measured at 208.0 nm and at 207.5 nm for MET and GUF, respectively. The proposed method showed good linearity over the concentration ranges of 1.0–110.0 and 1.0–90.0 µg/mL for MET and GUF, respectively with corresponding correlation coefficient of 0.9997 and 0.9999. The detection and quantitation limits for MET were found to be 0.021 and 0.064 µg/mL, respectively, while GUF corresponding values were 0.013 and 0.041 µg/mL. The method was successfully applied for determining MET and GUF in its dosage forms with high selectivity. The developed method produced comparable results to those obtained by the published reference methods in terms of precision and accuracy. A comprehensive assessment was carried out to evaluate the suggested method’s economic feasibility, practicality, and environmental sustainability compared to previously reported techniques. This comprehensive assessment leveraged several state-of-the-art tools, including the analytical Eco-scale, Green Analytical Procedure Index (GAPI), Analytical GREEnness (AGREE), Multi-Color Assessment, Analytical Green Star Area (AGSA) and Blueness Assessment Graphical Index tools. The suggested approach exhibited favorable quadrant profiles in GAPI assessment, along with higher AGREE, AGSA and Eco-scale scores, all of which confirmed their eco-friendliness.