Gas chromatographic–mass spectrometric analysis of d-limonene in human plasma

d-Limonene shows carminative and cholagogue effects and is used in treatment of gallstone, cholecystitis and angiocholitis. A simple method was developed to determine the concentration of d-limonene in human plasma. d-Limonene and internal standard (naphthalane, C10H18) were extracted with n-hexane and then injected to GC–MS. Calibration curves were linear (r = 0.9990, n = 6) in the range of 2–500 ng/ml for d-limonene in human plasma. Limit of detection and quantification were 0.5 and 2 ng/ml, respectively. This rapid and specific method was applied to the clinical pharmacokinetic investigation of d-limonene.