Comparison of protein precipitation, turbulent flow and automated on-line solid phase extraction, as plasma sample preparation techniques for the determination of compound I by LC-MS-MS

Compound I is a novel subtype-selective 5-HT1 receptor antagonist currently under pre-clinical investigation. A theoretical increase in sensitivity of about 4 times over the plasma protein precipitation method by the two on-line extraction systems tested should be expected due to the introduction of 100% of the analyte onto the column with both the on-line systems. The comparison of these three methods showed that the real gain in sensitivity was 4 times with Prospekt2(TM) and 2 times with TurboFlow(TM). This might be explained by the different mobile phases used combined with different recoveries. Due to the improved chromatography, the higher sensitivity and lower carry-over observed for this compound, the Prospekt2(TM) system was chosen in order to validate an analytical procedure for the quartitation of I in rat plasma followed by LC-MS-MS.