A micellar HPLC method for simultaneous determination of methocarbamol in three different tablets using single run; application to human plasma and evaluation of the method greenness

Methocarbamol is a well-known centrally acting skeletal muscle relaxant and is usually combined with analgesics like paracetamol, diclofenac and ibuprofen for treatment of musculoskeletal pain. A new approach based on applying green analytical procedures was proposed using micellar chromatographic method for the quantification of methocarbamol in three different combined dosage forms with isocratic mobile phase system in a single run in about 11 min. The separation was performed on C ₈ column (250 mm × 4.6 mm i.d., 5-μm particle size)with micellar mobile phase consisting of (0.12 M)sodium dodecyl sulfate, (15%)n-propanol, 0.02 M orthophosphoric acid, 0.3% triethylamine, adjusted to pH 6. The eluents were monitored by UV detection at 220 nm. The linearity of the method was acceptable over the concentration ranges of 5–200 μg/mL for methocarbamol, 5–80 μg/mL for paracetamol and 5–100 μg/mL for both diclofenac and ibuprofen. Also, the method was extended to determine methocarbamol in spiked human plasma. The validation of the developed method was evaluated based on ICH guidelines acceptance criteria for linearity, accuracy, precision and robustness. Moreover; the greenness profile of the proposed method was assessed and compared with the published HPLC methods using the analytical Eco-scale as an assessment tool.