Determination of menthol in plasma and urine of rats and humans by headspace solid phase microextraction and gas chromatography–mass spectrometry

A method for the determination of menthol and menthol glucuronide (M-G) after enzymatic hydrolysis in plasma and urine of rats and humans was developed using headspace solid phase microextraction and gas chromatography–mass spectrometry in the selected ion monitoring mode (HS-SPME/GC–MS). The assay linearity for plasma ranged from 5 to 1000 ng/ml. The limit of quantification (LOQ) in plasma was 5 ng/ml. The intra- and inter-day precision for menthol and M-G were ≤18.1% R.S.D. at the LOQ and ≤4.0% at higher concentrations. Menthol and M-G were determined in rat and human plasma and urine after administration of menthol.