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January 01, 2010 (Vol. 30, No. 1)

Automated Plasma Sample Preparation

Use of Total Aspiration and Dispense Monitoring Can Increase Utility of Liquid-Handling Systems

  • Challenging SPE Methods

    Click Image To Enlarge +
    Figure 2. 35 TADM-aspirate curves (A) and 35 TADM-dispense curves (B) obtained during an accuracy-and-precision test

    Labor-intensive methods such as SPE benefit most from the full automation possible with the Microlab Star. An SPE method typically begins with the conditioning of the SPE sorbent with an organic solvent followed by an aqueous one. The plasma sample aliquot is then diluted with a solution containing an internal standard compound and loaded on the SPE sorbent.

    The sorbent is rinsed with at least one solvent to remove proteins, salts, and other interferences. Finally, the analyte(s) of interest are eluted from the SPE sorbent with an organic solvent. These eluents are then evaporated, reconstituted, and analyzed on the LC/MS/MS instrument.

    When this SPE procedure is performed manually, a single analyst can only extract about 70 study samples per day. With automation on the Microlab Star, a single analyst can extract at least three times that many.

    We recently completed the bioanalysis of an approximately 1,300 sample clinical study using fully automated SPE on the Microlab Star, followed by analysis using ultra-performance liquid chromatography with tandem mass spectrometry detection (UPLC/MS/MS). The goal was to quantitate a parent drug along with five metabolites.

    The six analytes have a wide range of physicochemical properties, necessitating the use of multiple UPLC/MS/MS methods to achieve adequate sensitivity (<100 pg/mL). However, we were able to develop a single, fully automated SPE-extraction method utilizing a mixed-mode cation exchange/reversed-phase sorbent. With a single Microlab Star we were able to extract 1,288 samples in four days and complete the UPLC/MS/MS analyses on two UPLC/MS/MS instruments in about seven days. With traditional manual pipetting, the sample prep alone would have taken two weeks. The average QC sample accuracy (95–101%) and precision (≤6%) achieved during study sample analysis are typical of this method’s performance.

    In conclusion, the Hamilton Microlab Star with the TADM feature allows accurate, precise, and traceable plasma pipetting. Using the Microlab Star for fully automated plasma-preparation methods prior to LC/MS/MS analysis has increased our throughput at least threefold without any sacrifice in method performance, allowing us to deliver results to our clinical trials customers much faster.

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