MEPS as a rapid sample preparation method to handle unstable compounds in a complex matrix: determination of AZD3409...

The aim of the present investigation is to develop a simple, fast, and sensitive method for the determination of a new candidate drug, AZD3409, in rat, dog, and human plasma samples. AZD3409 is stable in aqueous solutions at low pH (< 4) but not in whole blood or in plasma. In rat plasma at 25 degrees C, more than 90% of the compound is degraded within 40 min. When 20 mg of NaF and 50 microL of protease inhibitor cocktail are added to 1.0 mL of rat blood, AZD3409 is stable for up to about 90 min. Due to the instability of AZD3409, microextraction in packed syringe (MEPS) is used as an online and fast sample-preparation method, followed by liquid chromatography-tandem mass spectrometry (LC-MS-MS) for the quantitation of this compound in plasma samples. In MEPS, the sampling sorbent is 1 mg of polystyrene polymer packed in a 250-microL syringe. When the plasma sample (50-250 microL) is withdrawn through the syringe by an autosampler, the analyte is adsorbed to the solid phase. The analyte is then eluted with an organic solvent such as methanol or the LC mobile phase (20-50 microL) directly into the instrument's injector. MEPS is rapid and easy to use. The lower limit of quantitation for AZD3409 is established to be 0.024 microM. The accuracy of the quality-control samples ranged from 89% to 102%, and the precision (C.V.%) had a value of 11-16% for the plasma samples. The calibration curve in plasma is obtained in the concentration range 0.022-9.0 microM. The coefficients of determination (R2) for plasma samples were > or = 0.998 for all runs. The present method is used for the analysis of rat and dog plasma samples.