Validation of a GC/MS method for the determination of tramadol in human plasma after intravenous bolus.

Tramadol quantitative determination by gas chromatography-mass spectrometry (GC/MS) using nefopam hydrochloride as internal standard (IS) and two calibration curves because of the large range of concentration attended in the plasmatic samples is described. Plasma samples drawn from subjects in postoperative period treated with two different initial intravenous (iv) bolus of tramadol (50 and 100 mg) followed by tramadol at the same infusion rate (12 mg h(-1)) are analysed. We operated for the qualitative analysis in Scan mode while for the quantitative analysis in SIM mode, selecting the ion m/z 58 for tramadol and m/z 179 for IS. The limit of detection (LOD) was 0.01 microg ml(-1) and the limit of quantification was 0.04 microg ml(-1).