Application of solid-phase extraction in the determination of U-82217 in rat serum, urine and brain

The techniques of solid-phase extraction (SPE) were applied in the analytical method development for the determination of U-82217, 3-(5-cyclopropyl-1,2,4-oxadiazol-3-yl)-5-[(4-methoxyphenyl)methyl] -imidazo[1,5-a]quinoxalin-4(5H)-one, in rat serum, urine and brain. Samples of serum, urine or brain homogenate containing U-82217 were loaded on C18 SPE columns and eluted with acetonitrile (300 microliters). The prepared samples were analyzed by reversed-phase HPLC using an ODS column with a mobile phase of acetonitrile-water (45:55, v/v) containing 0.12% of acetic acid (pH 6.0 +/- 0.1). The UV absorbance of the column effluent was monitored at a wavelength of 318 nm. The absolute extraction recovery from serum, urine and brain samples was ca. 90%. Linear calibration graphs were obtained over the ranges 5 ng/ml-20 micrograms/ml (serum), 20 ng/ml-20 micrograms/ml (urine) and 50 ng/g-200 micrograms/g (brain). The intra- and inter-assay precision and accuracy were all found to be < 13% at the concentrations evaluated. The strategy in SPE development and the application of this method to the determination of U-82217 in rat serum and brain for a pharmacokinetic study are also discussed.