Methadone d9

Reference substances furosemide, torasemide, atenolol, bisoprolol and metoprolol were obtained from Sigma-Aldrich GmbH (Steinheim, Germany). Hydrochlorothiazide (HCT), canrenone and nebivolol, as well as the deuterated internal standards (IS) ketamine-d₄, haloperidol-d₄, diazepam-d₅, quetiapine-d₈, oxazepam-d₅ and methadone-d₉ were purchased from LGC Standards GmbH (Wesel, Germany). HCT-d₂ was obtained from Toronto Research Chemicals (North York, Canada).
Acetonitrile was obtained from Karl Roth GmbH (Karlsruhe, Germany) and ethyl acetate from AppliChem (Darmstadt, Germany). Further chemicals and solvents used were supplied by Sigma-Aldrich GmbH (Steinheim, Germany). All reagents and solvents were either of analytical or LC grade.

Racemic methadone (1 mg/mL in Methanol) and methadone-D9 (100 μg/mL in Methanol) were obtained from LGC (Wesel, Germany). Methanol was obtained from JT Baker (Deventer, Netherlands), and acetone, methylene chloride, dichloromethane, propanol-2, acetic acid, ammonia, and sodium dihydrogen phosphate were obtained from Merck (Darmstadt, Germany). All reagents were analytical reagent grade. Bond-Elut Certify cartridges were supplied by Agilent Technologies (Santa Clara, CA, USA).