Sensitive quantification of atomoxetine in human plasma by HPLC with fluorescence detection using 4-(4,5-diphenyl-1H-imidazole-2-yl) benzoyl chloride derivatization.

The first HPLC-fluorescence method for the determination of atomoxetine in human plasma was developed and validated. Atomoxetine was derivatized with 4-(4,5-diphenyl-1H-imidazol-2-yl) benzoyl chloride (DIB-Cl) under mild conditions, and separated isocratically on a C18 column using a HPLC system with fluorescence detection (lambdaex: 318 nm, lambdaem: 448 nm). A linear calibration curve was obtained over the concentration range 1-1000 ng/mL (r=0.999). The limit of detection (S/N=3) was 0.3 ng/mL. The relative standard deviations of intra-day and inter-day variations were < or =8.30% and 7.47%, respectively. This method is rapid, sensitive, and suitable for both basic and clinical studies of atomoxetine.