Determination of pramipexole (U-98,528) in human plasma by high-performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry.

A highly sensitive and selective HPLC-MS-MS method was developed for the determination of pramipexole in human plasma. The analytes, pramipexole and BHT-920 (internal standard), were extracted from plasma at basic pH with methyl tert.-butyl ether (MTBE). MTBE was evaporated to dryness and reconstituted in 100 microliters of (95:5) methanol-water. Chromatographic separation was achieved on a Zorbax SB-CN column with a mobile phase of (15:5:80) water-0.1 M ammonium acetate-methanol. The analytes were detected utilizing HPLC in conjunction with atmospheric pressure chemical ionization (APCI) tandem mass spectrometry (MS-MS). The assay was linear in the concentration ranges of 50 to 5000 pg/ml. The analysis of pooled quality controls (150, 750, and 3000 pg/ml) demonstrated excellent precision with relative standard deviations (R.S.D.) (n = 18) of 7.2%, 5.3% and 5.2%, respectively. The method is accurate with all intra-day (n = 6) and overall (n = 18) mean values being less than 11.7% from theoretical.