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A novel 96-well screen filter plate (patent pending) has been invented to eliminate a time-consuming and labor-intensive step in preparation of in vivo study samples--to remove blood or plasma clots. These clots plug the pipet tips during a manual or automated sample-transfer step causing inaccurate pipetting or total pipetting failure. Traditionally, these blood and plasma clots are removed by picking them out manually one by one from each sample tube before any sample transfer can be made. This has significantly slowed the sample preparation process and has become a bottleneck for automated high-throughput sample preparation using robotic liquid handlers. Our novel screen filter plate was developed to solve this problem. The 96-well screen filter plate consists of 96 stainless steel wire-mesh screen tubes connected to the 96 openings of a top plate so that the screen filter plate can be readily inserted into a 96-well sample storage plate. Upon insertion, the blood and plasma clots are excluded from entering the screen tube while clear sample solutions flow freely into it. In this way, sample transfer can be easily completed by either manual or automated pipetting methods. In this report, three structurally diverse compounds were selected to evaluate and validate the use of the screen filter plate. The plasma samples of these compounds were transferred and processed in the presence and absence of the screen filter plate and then analyzed by LC-MS/MS methods. Our results showed a good agreement between the samples prepared with and without the screen filter plate, demonstrating the utility and efficiency of this novel device for preparation of blood and plasma samples. The device is simple, easy to use, and reusable. It can be employed for sample preparation of other biological fluids that contain floating particulates or aggregates.

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We have investigated various sample chromatographic extraction and sample preparation methods for liquid chromatography mass spectrometry analysis in order to increase the throughput of various in vivo and in vitro assays in support of drug discovery. The results indicated that direct plasma injection, although certainly faster than conventional protein precipitation for sample preparation, had problems associated with column longevity and overall robustness. Frequently a single study could not be completed without column replacement. On-line solid phase extraction, on the other hand, compared well with off-line solid phase extraction, using our LC extraction column design, as contamination of the extraction column was minimized by back flushing using the Gilson syringe pump. Finally, on-line solid phase extraction for support of Caco-2 permeability studies worked very well for both single components and mixtures as the matrix was much simpler, presenting fewer contamination problems.