Determination of amphetamine and methamphetamine in urine by solid phase extraction and ion-pair liquid chromatography–electrospray–tandem mass spectrometry

A method using a solid phase extraction (SPE) and ion-pair liquid chromatography–electrospray–tandem mass spectrometry (LC–ES–MS/MS) was developed for determination of amphetamine (Amp) and methamphetamine (mAmp) in urine samples. A reversed phase C18 column was utilized for LC separation and MS/MS was used for detection. Trifluoroacetic acid was added to the mobile phase as an ion-pairing reagent. MS2 was employed for quantitative determination. In addition, d8-amphetamine and d8-methamphetamine were used as internal standards. An Oasis HLB SPE cartridge, which has hydrophilic and lipophilic functions, was utilized for sample pre-treatment. Recoveries ranging from 97.3 to 102.1% were measured. Good linear ranges, 5–500 ng/ml, for Amp and mAmp were determined. The detection limit of each analytical compound, based on a signal-to-noise ratio of 3, was approximately 1 ng/ml. The applicability of this newly developed method was examined by analyzing several urine samples from drug users.