Solid-phase extraction in amphetamine and methamphetamine analysis of urine

A systematic evaluation that compares the recoveries of methamphetamine and amphetamine from spiked urine using C8, C18, strong cation exchanger (SCX), and C8-SCX mixed procedures (solid-phase extraction) is reported. Optimized experimental conditions including pH of the sample, solvent composition, and urine concentration for different solid-phase extraction sorbents were studied. The largest recoveries--greater than 86% for methamphetamine and greater than 88% for amphetamine--were achieved with a mixed adsorbent (C8-SCX) and mixed elution solvent CH2Cl2-i-propanol-NH4OH (78:20:2) at pH 6. The concentration of the urine matrix did not affect the extraction efficiency. The detection limits of methamphetamine and amphetamine in urine were obtained at 0.03 and 0.07 micrograms/mL, respectively, using gas chromatographic-mass spectrometric analysis operated in the electron impact mode.