Determination of ABT-089 in human plasma by high performance liquid chromatography using in situ precolumn derivatization with 7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole

ABT-089 is a potent, selective neuronal cholinergic channel modulator with cognition enhancing activity in several animal paradigms. A simple and sensitive chromatographic method for the specific determination of ABT-089 in human plasma has been developed and validated. The method utilizes in situ precolumn fluorescence derivatization of the sample with 7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-F) prior to liquid-liquid extraction followed by reverse phase HPLC and fluorescence detection (lambda(ex) 495 nm, lambda(em) 533 nm). The described method significantly simplifies sample preparation. The derivatized product was separated from interference using a YMC ODS-AQ, 5 microm, 250x4.6 mm i.d. column using a mobile phase consisting of 30:5:65 (v:v:v) acetonitrile/methanol/aqueous buffer at a flow rate of 0.75 ml min(-1). The aqueous buffer consisted of 0.01 M tetramethylammonium perchlorate, 0.1% (v:v) trifluoroacetic acid, pH 3.0. An Alltech Absorbosphere CN, 5 microm, cartridge guard column was also used before the analytical column. Plasma samples were alkalinized with 0.1 M NaHCO3, 300 microl of a 1 mg ml(-1) ethanolic solution of NBD-F was added and the samples were heated in a water bath for 10 min at 50 degrees C. The samples were then extracted with tert-butylmethylether, evaporated to dryness and then reconstituted in mobile phase. For 1 ml of plasma, a limit of quantitation (LOQ) of 1.6 ng ml(-1) was obtained. The method was linear from 1.6 to 836 ng ml(-1). Inter and intra-day assay RSD (n = 6) were less than 9%. Accuracy determinations showed the quality control samples to range between 88-114% of the theoretical concentration.