ISOLUTE® SLE+ User Guide (Supported Liquid Extraction)

Importance of the Topic

Supported liquid extraction (SLE) using ISOLUTE® SLE+ provides an efficient, reproducible approach to sample preparation for biological fluids. By immobilizing aqueous samples on a diatomaceous earth support and eluting analytes into a water-immiscible solvent, SLE eliminates emulsion issues and delivers cleaner extracts, lower limits of quantitation and improved reproducibility for LC-MS/MS and GC-MS workflows.

Objectives and Overview

This guide describes the development of SLE methods with ISOLUTE® SLE+ plates and columns, covering the extraction mechanism, removal of proteins and phospholipids, automation strategies, method development for different analyte classes, scalability and troubleshooting.

Methodology

SLE follows a three-step load-wait-elute protocol: aqueous sample application, dispersion and absorption on the SLE support, then partitioning into an organic solvent (e.g. MTBE, ethyl acetate, dichloromethane or hexane). pH adjustment with volatile buffers (formate, acetate, ammonium hydroxide) optimizes extraction of acidic, neutral and basic compounds. Typical loading volumes range from 10 µL to 10 mL per format, with elution performed under gravity and a brief vacuum or positive pressure pulse to maximize recovery.

Instrumentation Used

• Biotage® Extrahera™ automated eight-channel workstation for SLE, SPE, protein precipitation and phospholipid depletion methods.
• Biotage® VacMaster™ vacuum manifolds (96, 10, 20 positions) and PRESSURE+ positive-pressure manifolds (96, 48-well) for manual processing.
• Biotage® SPE Dry 96 and SPE Dry 96 Dual microplate concentrators for high-throughput evaporation.
• TurboVap® and TurboVap® LV automated systems for solvent removal and sample concentration.

Main Results and Discussion

ISOLUTE® SLE+ consistently removed >95% of phospholipids and proteins, outperforming protein precipitation and dedicated depletion cartridges. Recoveries greater than 80% were achieved for tricyclic antidepressants, β-blockers, endogenous steroids, NSAIDs and fat-soluble vitamins. Scalability tests from 200 µL to 10 mL formats showed uniform performance. Automation with the Extrahera system reduced processing time by approximately one third versus manual methods.

Contributions and Practical Use

• Delivers cleaner extracts with minimal matrix effects for LC-MS/MS quantitation.
• Eliminates emulsions and manual mixing steps common to traditional LLE.
• Supports rapid method development via standardized pH and solvent screens.
• Integrates seamlessly with manual and automated workflows, increasing throughput.
• Handles a wide analyte polarity range through pH control and ion-pair strategies.

Future Trends and Applications

Advances may include further miniaturization of formats, new solvent systems tailored to emerging analytes, integration with high-resolution and ambient ionization mass spectrometry, and expanded use in metabolomics, clinical diagnostics and environmental monitoring.

Conclusion

ISOLUTE® SLE+ supported liquid extraction offers a robust, versatile and automation-friendly platform for high-purity sample preparation. Its efficient removal of proteins and phospholipids, broad analyte compatibility and scalability make it an essential tool for modern analytical laboratories.

References

No external references cited.