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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.

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According to Lenz's law, the magnetic field from the oscillating magnetic probe will induce out-of-plane surface magnetic domains (SMDs) from the in-plane magnetization at the locally tapped points on a ferromagnetic La(0.7)Sr(0.3)MnO3 (LSMO) thin film. It was possible to control and manipulate the out-of-plane SMDs by varying the tapping intervals and changing the scanning direction. We also found that the anisotropic stresses from the out-of-plane SMDs caused the appearance of large-area straight striped domain structures on the order of several micrometers. Smaller oscillating magnetic probe tapping intervals produced larger periods (or widths) of the straight striped domain structure.