title: Determination of tramadol and O-desmethyltramadol in human plasma by high-performance liquid chromatography with mass spectrometry detection.
abstract: A new simple, sensitive and selective liquid chromatography coupled with mass spectrometry (LC/MS) method for quantification of tramadol and its active metabolite O-desmethyltramadol in human plasma was validated. The tramadol and its metabolite were separated on a reversed phase column (Zorbax SB-C18, 100 mm x 3.0 mm I.D., 3.5 microm) under isocratic conditions using a mobile phase of a 10:90 (v/v) mixture of acetonitrile and 0.2% (v/v) trifluoroacetic acid in water. The flow rate was 1 ml/min at the column temperature 45 degrees C. In these chromatographic conditions, the retention times were 2.3 min for O-desmethyltramadol and 3.5 min for tramadol, respectively. The detection of both analytes was in SIM mode using an ion trap mass spectrometer with electrospray positive ionisation. The monitored ions were m/z 264 for tramadol and m/z 250 for its metabolite. The sample preparation was very simple and rapid and consisted in plasma protein precipitation from 0.2 ml plasma using 0.2 ml solution of perchloric acid 7%. Calibration curves were generated over the range of 2-300 ng/ml for both analytes with values for coefficient of correlation greater than 0.998 and by using a weighted (1/y) quadratic regression. The values of precision and accuracy for tramadol at quantification limit were less than 10.9% and 5.1, respectively, both for within- and between-run. For O-desmethyltramadol, precision and accuracy at quantification limit were 10.1% and -9.9% for within-run determinations and 6.7% and 10.4% for between-run determinations, respectively. The mean recovery for both analytes was 96%. Both tramadol and its metabolite demonstrated good short-term, long-term, post-preparative and freeze-thaw stability. This is the first reported method for analysis of tramadol and O-desmethyltramadol in human plasma that uses protein precipitation as sample processing procedure. The method is very simple and allows obtaining a very good recovery of both analytes. The validated LC/MS method has been applied to a pharmacokinetic study of 50 mg tramadol tablets on healthy volunteers.
authors.affiliation: Faculty of Pharmacy, University of Medicine and Pharmacy Iuliu Hatieganu, Emil Isac 13, RO-400023, Cluj-Napoca, Romania.
authors.forename: Laurian
authors.initials: L
authors.lastname: Vlase
authors.forename: Sorin E
authors.initials: SE
authors.lastname: Leucuta
authors.forename: Silvia
authors.initials: S
authors.lastname: Imre
mesh_terms: D000284:Administration, Oral; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization; D013997:Time Factors; D014147:Tramadol / Q000031:analogs & derivatives* / Q000097:blood* / Q000378:metabolism
chemical_list: C080580:O-demethyltramadol; D014147:Tramadol