Development and Validation of a Chiral HPLC Method for the Quantitation of Methocarbamol Enantiomers in Human Plasma

An isocratic chiral HPLC method was developed and validated for the quantitation of methocarbamol enantiomers in human plasma. Methocarbamol and an internal standard were extracted with ethyl ether. Chiral separation was achieved on coupled Spherisorb CN and Chiralcel OD columns with a mobile phase of ethanol—hexane (30:70, v/v). The detection was by UV at 272 nm. Linearity was established at 0.5–50 μg/ml (r < 0.998). Interday precision and accuracy of the calibration standards were demonstrated by 0.8 to 9.4% coefficients of variance (C.V.) and −5.2 to +3.8% relative error (R.E.). Quality controls showed interday precision and accuracy of 4.4 to 7.2% C.V. and +0.4 to +5.5% R.E. Recovery of methocarbamol enantiomers was 77–84%. No interconversion of the methocarbamol enantiomers was observed during process of storage, extraction nor chromatograph. Reproducibility and stability of the analytical columns were demonstrated.