Analysis of fluorescein isothiocyanate derivatized amphetamine and analogsin human urine by capillary electrophoresis in chip-based and fused-silicacapillary instrumentation

Amines can easily be derivatized with fluorescein isothiocyanate isomer I ( FITC) and analyzed by capillary electrophoresis (CE) using alkaline buffers with or without dodecyl sulfate micelles. This paper reports the CE analys is of FITC-derivatized amphetamine, methamphetamine, 3,4-methylenedioxymeth amphetamine and beta-phenylethylamine in human urine using chip-based and f used-silica capillary instrumentation with laser-induced fluorescence detec tion. Data obtained via direct labeling of fortified urine are compared to those generated after FITC labeling of urinary extracts that were prepared by solid-phase extraction using a copolymer phase. For a urine volume of 5 mL with a "spiked amine": FITC ratio of 1:250, the latter approach was foun d to provide a sensitivity that Is relevant for toxicological drug screenin g and confirmation (about 200 ng/mL urine). With direct labeling of 10 mu L urine that was alkalinized and diluted for derivatization, the limit of id entification was determined to be about 10 mu g/mL, a value that is too hig h for practical purposes. Compared to fused-silica capillaries, electrophor esis in microstructures is shown to provide faster separations and higher e fficiencies without loss of accuracy and precision.