Determination of dextromethorphan and its metabolite dextrorphan in human urine by capillary gas chromatography without derivatization

Abstract

A sensitive, simple and accurate method was developed for determination of dextromethorphan (DM) and dextrorphan (DT) in human urine by capillary gas chromatography without derivatization. After an oral dose of 30 mg DM, urine samples were collected and extracted, then analyzed on 0.22 mm×17 m HP-1 capillary column. DM and its metabolite DT were analyzed simultaneously with good separation. Docosane was used as the internal standard (I.S.). The detector used was flame ionization detector (FID). There was a linear relationship between peak area ratios of analytes to I.S. and concentration of analytes over the concentration range 0.37–7.38 μmol/l for DM and 0.39–77.8 μmol/l for DT. The recovery was 88.1∼103.9% for DM and 86.7∼96.8% for DT. The within-day and between-day coefficients of variation were less than 7.4 and 7.3% (RSD) for the assay of DM and DT in urine, respectively. The limits of detection (LOD) were 0.30 μmol/l for DM and 0.16 μmol/l for DT. The limits of quantitation (LOQ) were 0.37 μmol/l (RSD<6%) for DM and 0.39 μmol/l (RSD<7%) for DT. The method has been applied to determine the oxidative phenotypes of cytochrome P450 2D6 ( CYP2D6) in a Chinese population with metabolic ratio of DM in human urine.