Automated Solid Phase Extraction (SPE) Method Development using Oasis Mixed Mode Sorbent Selection Plate

Importance of the Topic

Modern quantitative LC-MS analysis of biological matrices demands efficient sample cleanup to remove interfering components and protect analytical instruments. Mixed-mode solid phase extraction (SPE) offers versatile retention mechanisms for simultaneous removal of matrix interferences and enrichment of target analytes. Automating SPE method development accelerates optimization, reduces manual errors and ensures reproducible results in high-throughput laboratories.

Objectives and Study Overview

This study demonstrates the automated development of mixed-mode SPE methods using the Oasis 2x4 sorbent selection plate. The goal was to leverage four distinct mixed-mode sorbents and two standard protocols to identify optimal extraction conditions for a set of analytes in spiked human plasma. The workflow was implemented on the Andrew+ pipetting robot to compare performance and time savings against manual processing.

Methodology

The established Oasis 2x4 method involves loading samples on plates containing four mixed-mode sorbents, followed by a wash and elution protocol. Automation was achieved using the Andrew+ pipetting robot programmed via the browser-based OneLab software. The setup included:

• Three single- and multi-channel pipettes (10-300 µL, 5-120 µL, 50-1200 µL).
• A SPE vacuum manifold and deepwell microplate for sorbent plate handling.
• Reservoirs, tip racks and a 50 mL conical tube for reagent storage.

Instrumentation

Post-extraction quantitation was performed on a Waters ACQUITY UPLC I-Class system coupled to a Xevo TQ-S mass spectrometer. Multiple reaction monitoring in both positive and negative ionization modes enabled sensitive measurement of target analytes.

Main Results and Discussion

Automation of the 2x4 sorbent selection workflow reduced method development time from over four hours manually to under one hour using Andrew+. High reproducibility was demonstrated across eight replicates of four analytes in human plasma. The streamlined process minimized pipetting errors and consistent vacuum control improved elution efficiency.

Benefits and Practical Applications

Automating SPE method development offers several advantages:

• Significant time savings, enabling rapid screening of sorbent conditions.
• Improved reproducibility by eliminating manual variability.
• Scalability for high-throughput bioanalysis and QA/QC laboratories.
• Reduced training requirements and operator dependency.

Conclusion

The integration of the Oasis 2x4 sorbent plate with the Andrew+ pipetting robot provides a fast, reliable and user-friendly platform for mixed-mode SPE method development. This approach streamlines workflow, enhances data quality and frees analytical scientists to focus on data interpretation rather than manual protocol steps.

Future Trends and Applications

Future developments may include further integration with online LC-MS systems, advanced software algorithms for automated condition selection and expansion to other sorbent chemistries. The trend toward fully automated sample preparation will support increasingly complex matrices and large sample cohorts in pharmaceutical, clinical and environmental analytics.