ONLINE DERIVATIZATION INTO PRECOLUMNS FOR THE DETERMINATION OF DRUGS BY LIQUID-CHROMATOGRAPHY AND COLUMN-SWITCHING - DETERMINATION OF AMPHETAMINES IN URINE

A chromatographic system for the on-line derivatization of drugs using column switching is described. The system uses a 20 mm x 2.1 mm i.d. precolumn packed with a unmodified ODS stationary phase. This column i s used for sample cleanup and enrichment of the analytes. Next, the tr apped analytes are derivatized by injection of the derivatization reag ent into the precolumn. Finally, the derivatives are transferred to th e analytical column for their separation under reversed-phase conditio ns. The influence of several parameters such as the reaction time, the amount of derivatization reagent, or the system design has been studi ed using some amphetamines as model compounds and three derivatization reagents: sodium 1,2-naphthoquinone-4-sulfonate, o-phthaldialdehyde, and 9-fluorenylmethyl chloroformate. The potential of the described ap proach is illustrated by determining amphetamine and methamphetamine i n untreated urine at ambient temperature.