Simultaneous determination of illicit drugs in human urine by liquid chromatography mass spectrometry

The method for simultaneous determination and confirmation of illicit drugs (e.g., methamphetamine, amphetamine, ephedrine, methylephedrine, morphine, morphine-3-glucuronide, morphine-6-glucuronide, 6-acetylmorphine, cocaine, and benzoylecgonine) in human urine by thermospray liquid chromatography-mass spectrometry (LC-MS) was studied. The LC-MS separation was performed on a reversed phase column (L-column ODS; 150 mm x 4.6-mm i.d.) using a gradient mobile phase system of 100mM ammonium acetate for 1 min then linear ramps to 100mM ammonium acetate including 40% acetonitrile at 20 min. Extraction was conducted by solid-phase extraction using a Sep- pak C18 cartridge. The drugs were eluted with 2 mL of 40% acetonitrile in 100mM ammonium acetate, pH3 (adjusted with acetic acid), from the cartridge. A 50-μL volume of the eluate was injected into the LC-MS. The recoveries by this extraction were 88 to 99%. The mass spectra of methamphetamine, amphetamine, ephedrine, methylephedrine, morphine, 6-acetylmorphine, cocaine, and benzoylecgonine showed the quasi-molecular [M+H]+ ion as the base peak, whereas morphine-3-glucuronide and morphine-6-glucuronide showed [MH-glucuronide]+ ion as the base peak. The calibration graphs were linear and reproducible. Detection limits of these drugs ranged from 2 to 40 ng/mL by selected ion monitoring (SIM) mode and from 50 to 400 ng/mL by scan mode. The coefficients of variation for the analysis of these drugs ranged from 4.5 to 9.5% at a concentration of 0.4 μg/mL (n = 10).