Stereoselective determination of methadone and the primary metabolite EDDP in human plasma by automated on-line extraction and liquid chromatography mass spectrometry.
A sensitive stereoselective bioanalytical liquid chromatographic assay with mass spectrometric detection (LC-MS) was developed and validated for the on-line extraction and quantification of R- and S-methadone and the primary metabolite R- and S-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) from human plasma. Deproteinized plasma was injected directly onto a small C8 column, washed and then back-flushed using a column switching valve and a second pump onto an alpha1-acid glycoprotein analytical column, and enantioselective separation achieved using a mobile phase gradient of methanol and ammonium formate. Analytes were validated over a range of 0.1-25 ng/ml R- and S-EDDP and 0.1-100ng/ml R- and S-methadone, respectively. Unweighted standard curves were linear over this concentration range (regression coefficients > 0.999). Quality control samples were evaluated at 1, 5, 12.5 ng/ml R- and S-EDDP and 1, 10, 50 ng/ml R- and S-methadone. Intra- and inter-day accuracy was >95%, and intra- and inter-day coefficients of variation were less than 10% for all analytes and concentrations. This assay represents the only method currently available which combines on-line extraction and achieves chiral separation of both methadone and EDDP from plasma, and offers improvements in sensitivity over existing methods.
Whittington
Dale
D
Department of Anesthesiology, University of Washington, Box 356540, 1959 NE Pacific St. RR-442, Seattle, WA, USA.
Sheffels
Pam
P
Kharasch
Evan D
ED
D001331:Automation; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D008691:Methadone / Q000097:blood*; D011759:Pyrrolidines / Q000097:blood*; D012680:Sensitivity and Specificity
D011759:Pyrrolidines; D008691:Methadone; C010724:2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine