Rapid Mixed-Mode SPE Method Development Using the Oasis® μElution Sorbent Selection Plate

Importance of the Topic

Rapid screening and optimization of solid phase extraction (SPE) methods is essential in pharmaceutical bioanalysis to achieve high recovery, low matrix effects, and efficient workflows. Mixed-mode SPE combines multiple interaction mechanisms in a single sorbent, allowing broad analyte coverage and improved selectivity. The Oasis® μElution Sorbent Selection Plate provides an integrated platform for parallel evaluation of four mixed-mode sorbents, accelerating method development and reducing solvent consumption.

Objectives and Study Overview

This application note describes a streamlined approach for mixed-mode SPE method development using the Oasis Method Development μElution Plate. Key goals include:

• Screening four sorbent chemistries (MCX, WAX, WCX, MAX) in a single experiment
• Applying two standardized protocols to evaluate neutral, acidic, and basic pharmaceuticals
• Demonstrating the workflow with abrocitinib and enzalutamide as model analytes

Methodology and Instrumentation

The workflow employs a 2×4 well μElution plate containing four Oasis mixed-mode sorbents. The generic protocol steps are:

• Conditioning each well with organic and aqueous solvents
• Loading plasma samples spiked with target analytes
• Washing to remove matrix interferences
• Eluting two fractions: a neutral or non-ionic fraction followed by a mixed-mode fraction

The microelution format minimizes solvent volumes and eliminates evaporation steps. Quantitative analysis is performed by LC-MS/MS, ensuring sensitive detection of the pharmaceutical compounds.

Main Results and Discussion

Recovery and selectivity data indicate that the MCX sorbent provided the best overall performance:

• Abrocitinib: 92% recovery in the neutral fraction (Elute 1) on MCX
• Enzalutamide: 106% recovery in the mixed-mode fraction (Elute 2) on MCX

Other sorbents (WAX, WCX, MAX) yielded moderate recoveries, illustrating the need for mixed-mode screening to identify the optimal chemistry. Matrix effects were low across all sorbents, highlighting the clean-up efficiency of the protocol.

Benefits and Practical Applications

The mixed-mode μElution approach offers several advantages:

• High throughput: simultaneous evaluation of four sorbents in one plate
• Reduced development time: only two generic protocols are required
• Solvent and sample savings: microelution format minimizes volumes
• Robust performance: high recoveries and low matrix effects for diverse analytes

This method is ideal for early-stage method development in pharmaceutical and bioanalytical laboratories.

Future Trends and Opportunities

Advancements likely to enhance mixed-mode SPE include:

• Integration with automated liquid handling for fully walk-away workflows
• Expansion of sorbent chemistries to target emerging analyte classes
• Miniaturization and online SPE coupling directly to LC-MS instruments
• Data-driven selection of sorbent protocols using machine learning

Conclusion

The Oasis Method Development μElution Plate enables rapid, parallel screening of mixed-mode sorbents, delivering high analyte recovery and clean extracts in a single experiment. The approach streamlines bioanalytical SPE method development, offering significant time and resource savings.

References

Trudeau M., Lee M. Rapid Mixed-Mode SPE Method Development Using the Oasis® μElution Sorbent Selection Plate. Waters Corporation, Application Brief, July 2024.