SIMULTANEOUS DETERMINATION OF METHOCARBAMOL AND IBUPROFEN IN THEIR BINARY MIXTURES USING HPLC METHOD WITH FLUORESCENCE DETECTION: APPLICATION TO COMBINED TABLETS

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A new simple, rapid, and sensitive reversed-phase liquid chromatographic method was developed and validated for the simultaneous determination of methocarbamol (MET) and ibuprofen (IBU) in their combined dosage form. The separation of these compounds was achieved within 7.0 min on a CLC Shim-pack C8 column (250 × 4.6 mm, 5-µm particle size) using isocratic mobile phase containing a mixture of methanol and 0.05 M dihydrogen phosphate buffer (75:25, v/v) at pH 6.5. The analysis was performed at a flow rate of 1.0 mL/min with fluorescence-detection at 295 nm after excitation at 224 nm. The selectivity, linearity of calibration, accuracy, intra- and inter-day precision and recovery were examined as parts of the method validation. The concentration–response relationship was linear over a concentration range of 0.05–0.50 µg/mL for MET and 0.03–0.50 µg/mL for IBU with a limit of detection 3.8 ng/mL and 1.6 ng/mL for MET and IBU, respectively. The proposed method was applied for the simultaneous determination of the two studied drugs in their combined tablets with average recoveries of 100.75 ± 1.01% and 99.25 ± 1.16% for MET and IBU, respectively. The results were favorably compared to those obtained by the USP reference methods.