Derivatization of tertiary amphetamines with 9-fluorenylmethyl chloroformate for liquid chromatography: determination of N-methylephedrine

Abstract

The fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC) was evaluated for the derivatization of tertiary amphetamines prior to liquid chromatographic analysis. Conditions for the derivatization were investigated, including the reaction time, the derivatization reagent concentration and the pH, using N-methylephedrine as a model compound. On the basis of these studies, a method for the quantification of N-methylephedrine is presented. The method involves derivatization with FMOC at ambient temperature and separation of the derivatives formed on a LiChrospher C₁₈, 5 μm, 125 × 4 mm id column using acetonitrile–water gradient elution. The proposed procedure shows good linearity, accuracy and reproducibility in the 1.0–25.0 μg mL⁻¹ concentration range. The limit of detection was 0.1 μg mL⁻¹ and the limit of quantification was 0.5 μg mL⁻¹. The utility of the assay was demonstrated by determining N-methylephedrine in water and urine samples.