Oasis HLB Cartridges and 96-Well Plates

Significance of the Topic

Solid phase extraction with hydrophilic-lipophilic-balanced polymeric sorbents has become indispensable for isolating acidic, neutral, and basic compounds across clinical, environmental, food, and industrial applications. The universal Oasis HLB sorbent combines N-vinylpyrrolidone and divinylbenzene to deliver exceptional retention capacity, pH stability from 1 to 14, and compatibility with a broad solvent range.

Objectives and Overview

This manual outlines best practices for sample pretreatment and optimized SPE workflows using Oasis HLB cartridges and 96-well plates. The goals are to achieve high recoveries (>85%), low variability (<5% RSD), and method robustness for diverse matrices such as plasma, urine, soil, beverages, and large-volume water samples.

Methodology and Instrumentation

Sample pretreatment varies by matrix:

• Biological fluids: dilute 1:1 with acidified or basified water, spike internal standards, clarify by centrifugation.
• Solid materials: homogenize, extract with aqueous or organic solvent, adjust pH or exchange solvent as needed.
• Aqueous samples: adjust pH, remove particulates by filtration or centrifugation.
• Non-aqueous liquids: dilute with aqueous buffers and co-solvents for reversed-phase or mixed-mode SPE.

Key SPE steps include conditioning with methanol, equilibration in water, sample loading at ≤1 mL/min, sequential washes (e.g., 5% MeOH, pH-adjusted solvents), and elution with organic modifiers.

Instrumentation:

• Oasis HLB cartridges or 96-well plates
• Adjustable vacuum manifold (5" Hg)
• Centrifuge (up to 8,000 × g)
• Solvent reservoirs for methanol, water, acid/base modifiers
• Evaporation/reconstitution unit

Key Results and Discussion

The generic SPE method provides broad applicability, high recoveries, and consistent performance. A two-dimensional optimization strategy—varying pH and organic solvent concentration—enables cleaner extracts by selectively retaining target analytes while removing interferences. A 20-bottle optimization exemplifies the process: sequential base and acid washes yield recoveries >90% for model compounds.

Benefits and Practical Applications

Oasis HLB offers:

• Enhanced retention of polar and nonpolar analytes
• Resistance to extreme pH and solvent conditions
• High throughput with 96-well plate formats and µelution
• Scalable workflows for small and large volume samples

Future Trends and Potential Applications

Emerging directions include integration with automated robotics, online SPE-LC-MS/MS hyphenation, microelution for ultra-low volume samples, and data-driven method development using chemometric or machine-learning approaches. Novel sorbents with tailored mixed-mode interactions will further expand selectivity.

Conclusion

Waters Oasis HLB sorbent provides a versatile, robust SPE platform for acidic, neutral, and basic analytes across diverse matrices. By fine-tuning pH and solvent composition, analysts can achieve high recoveries, improved reproducibility, and streamlined workflows for routine and research laboratories.

Reference

• Waters Corporation. Oasis HLB Cartridges and 96-Well Plates Care and Use Manual; April 2014.