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

The fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC) was evaluate d for the derivatization of tertiary amphetamines prior to liquid chromatog raphic analysis. Conditions for the derivatization were investigated, inclu ding the reaction time, the derivatization reagent concentration and the pH , using N-methylephedrine as a model compound. On the basis of these studie s, a method for the quantification of N-methylephedrine is presented. The m ethod involves derivatization with FMOC at ambient temperature and separati on of the derivatives formed on a LiChrospher C-18, 5 mu m, 125 x 4 mm id c olumn using acetonitrile-water gradient elution. The proposed procedure sho ws good linearity, accuracy and reproducibility in the 1.0-25.0 mu g mL(-1) concentration range. The limit of detection was 0.1 mu g mL(-1) and the li mit of quantification was 0.5 mu g mL(-1). The utility of the assay was dem onstrated by determining N-methylephedrine in water and urine samples.