We have developed a fluorescence detection-liquid chromatography (HPLC-FL) method that involves sample pretreatment by solid-phase dispersive extraction (SPDE) and solid-phase fluorescence derivatization for the simple and rapid analysis of methamphetamine (MA) in urine. This method uses a reversed-phase polymeric solid-phase gel to clean up analytes in SPDE, followed by fluorescence derivatization with 9-fluorenylmethyl chloroformate (FMOC) in the solid-phase. The optimal conditions for SPDE and solid-phase fluorescence derivatization were obtained when J-SPEC PEP was used as the solid-phase gel and 0.5 mmol/L FMOC in 50 mmol/L borate buffer solution (pH 10) was used as the fluorescence derivatization reagent. The recovery experiment of MA in urine yielded a clean chromatogram with no interfering peaks, demonstrating the validity of our method; the recoveries were 83.6% when spiked at a low concentration level (100 ng/mL) and 80.7% when spiked at a high concentration level (1000 ng/mL). Compared with the conventional liquid-phase method, the reaction product (FMOC-MA) of solid-phase fluorescence derivatization had higher stability. Reaction rate constants were calculated by changing the temperature conditions, and physicochemical parameters, including activation energy and activation entropy involved in the degradation reaction, were obtained from the Arrhenius plot and analyzed thermodynamically. Taken together, our results suggest that the HPLC-FL method with SPDE and solid-phase fluorescence derivatization for sample pretreatment provides a simple and rapid means of analyzing MA in urine samples.
Keywords: 9-fluorenylmethyl chloroformate; HPLC; methamphetamine; solid-phase dispersive extraction; solid-phase fluorescence derivatization.