Oasis Cartridges and 96-Well Plates

Importance of the Topic

Solid-phase extraction (SPE) is a cornerstone of modern analytical chemistry, enabling reliable cleanup and concentration of complex samples prior to instrumental analysis. The Oasis family of polymer-based SPE sorbents combines hydrophilic and lipophilic properties in a water-wettable matrix, delivering consistent performance over a wide pH and solvent range. By simplifying workflows, reducing sample-to-sample variability, and improving recovery of acidic, basic, and neutral analytes, Oasis cartridges and 96-well plates address critical needs in pharmaceutical, food safety, environmental, and clinical testing.

Objectives and Overview

This manual provides end-to-end guidance for using Oasis HLB, PRiME HLB, MCX, MAX, WCX, WAX, and mixed-mode sorbents in cartridge and plate formats. It outlines generic and targeted SPE protocols for a range of matrices—biological fluids, foods, soils, beverages, oils, and environmental waters. Key goals include:

• Presenting standardized sample pre-treatment recommendations.
• Describing conditioning, loading, washing, elution, and troubleshooting steps for each sorbent chemistry.
• Offering optimization strategies based on pH and organic composition.
• Detailing specialized methods for multi-residue contaminant analysis, peptides bioanalysis, and PFAS monitoring.

Methodology and Instrumentation

Protocols follow a step-wise SPE workflow: conditioning (optional for water-wettable sorbents), sample loading, wash(s), and elution. Generic methods for Oasis HLB use 5% methanol washes and methanol or stronger solvents (acetonitrile, ethyl acetate) modified with acid or base. The 2-step pass-through PRiME HLB protocol employs high-organic loading and a single wash to remove phospholipids, yielding cleaner extracts in fewer steps. Mixed-mode MCX and WAX sorbents use pH control and successive washes to separate ionizable analytes. Method optimization uses a two-dimensional “20-bottle” approach, varying pH and methanol percentage to maximize selectivity. Sample pre-treatment may include dilution with acid/base buffers, centrifugation, homogenization, QuEChERS salts, or hexane partitioning for oils. Instrumentation typically involves vacuum or positive-pressure manifolds, centrifuges, mixers/vortexers, evaporators, and LC-MS/MS or GC-MS systems.

Main Results and Discussion

Oasis sorbents deliver:

• High recoveries (>85%) and low RSD (<5%) across a broad polarity range.
• Exceptional retention of polar compounds even if beds run dry.
• Water-wettable properties that eliminate conditioning/equilibration steps in PRiME variants.
• Efficient removal of matrix interferences, including >99% phospholipid clearance from biological extracts.
• Reproducible flows in cartridges, 96-well and µElution plates for high-throughput workflows.

Specialized methods described include multiresidue drug and pesticide workflows in food, mycotoxin analysis in grains, peptide bioanalysis using PST µElution, and PFAS monitoring with WAX and dual-phase WAX/GCB sorbents meeting regulatory requirements.

Benefits and Practical Applications

By integrating Oasis SPE into analytical routines, laboratories achieve:

• Streamlined sample prep with simplified protocols and reduced solvent consumption.
• Robust cleanup for challenging matrices in pharmaceutical, food safety, clinical, and environmental laboratories.
• High throughput capabilities using 96-well and µElution formats compatible with automation.
• Enhanced sensitivity and reproducibility in LC-MS/MS and GC-MS analyses.

Future Trends and Opportunities

Emerging needs in trace analyte monitoring, biologic drug development, and regulatory compliance will drive further innovation in SPE chemistries and formats. Potential developments include:

• Miniaturized and microfluidic SPE devices for ultra-low volume samples.
• Integration with online SPE-LC and automated platforms for real-time monitoring.
• New sorbent chemistries targeting next-generation contaminants and biomolecules.
• Expansion of PFAS and peptide analysis kits to meet tightening regulations and sensitivity demands.

Conclusion

The Oasis portfolio offers a versatile toolbox for effective sample preparation across diverse analytical challenges. Its water-wettable, high-capacity sorbents and simplified protocols promote reproducible, high-recovery extractions while minimizing method development time. Adopting Oasis SPE technologies enables laboratories to elevate data quality, throughput, and compliance in complex analyses.

Reference

Waters Corporation. Care and Use Manual for Oasis Cartridges and 96-Well Plates. 2024.