Assay of tramadol in urine by capillary electrophoresis using laser-induced native fluorescence detection

Capillary electrophoresis (CE) with UV laser-induced native fluorescence de tection was developed as a sensitive and selective assay for the direct det ermination of tramadol in human urine without extraction or preconcentratio n. The main problem in CE is the small inner diameter of the capillary whic h causes a low sensitivity with instruments equipped with a UV detector. La ser-induced native fluorescence with a frequency doubled argon ion laser at an excitation wavelength of 257 nm was used for the direct assay of tramad ol in urine to enhance the limit of detection about 1000-fold compared to U V absorption detection. The detection system consists of an imaging spectro graph and an intensified CCD camera, which views an illuminated 1.5 mm sect ion of the capillary. This set-up is able to record the whole emission spec tra of the analytes to achieve additionally wavelength-resolved electropher ograms. In the concentration range of 20 ng/ml-5 mu g/ml in human urine coe fficients of correlation were better than 0.998. Within-day variation deter mined on four different concentrations showed accuracies ranging from 90.2 to 108.4%. The relative standard deviation (RSD) was determined to be less than 10%. Day-to-day variation presented accuracies ranging from 90.9 to 10 3.1% with an RSD less than 8%. (C) 2000 Elsevier Science B.V. All rights re served.