The Use of ISOLUTE® HM-N for Rapid Sample Preparation

Importance of the Topic

Effective sample preparation is critical for accurate analysis of lipophilic compounds in complex aqueous matrices such as biological fluids and pharmaceutical formulations. Traditional liquid–liquid extraction methods often require laborious steps and risk emulsion formation. Supported liquid extraction using a diatomaceous earth material offers a streamlined, high-throughput alternative with broad applicability in modern analytical workflows.

Objectives and Study Overview

This study evaluates ISOLUTE HM-N, a chemically inert, modified diatomaceous earth sorbent, for rapid supported liquid extraction (SLE). The primary goals are to assess its aqueous sample capacity, extraction efficiency across a wide pH range, solvent consumption, and applicability to diverse sample types and volumes.

Methodology

The supported liquid extraction procedure comprises three key steps:

• Apply the aqueous sample (up to 75% of the column bed volume) onto the ISOLUTE HM-N column and allow adsorption for 5–15 minutes.
• Introduce a water-immiscible organic solvent (avoiding more than 10% water-miscible components) to elute the retained analytes.
• Collect the purified extracts for downstream analysis by LC-MS/MS, GC-MS, or other techniques.

Column capacity ranges from 0.3 mL to 20 mL of sample, with suggested elution volumes between 3 mL and 40 mL depending on column size.

Instrumentation

The work employs Biotage ISOLUTE HM-N SLE columns and a dedicated gravity rack system made of solvent-resistant polyethylene. The rack accommodates up to twenty 5 mL or ten 20 mL columns and is fitted with stainless steel or optional PTFE needles and stopcock assemblies for high solvent resistance and sample purity.

Main Results and Discussion

ISOLUTE HM-N exhibits high capacity for aqueous phase adsorption and enables efficient liquid–liquid extraction without emulsion formation. The large interfacial surface area accelerates mass transfer, yielding clean extracts. The sorbent is stable in the pH range 1–13, allowing enhanced recovery of ionizable compounds by applying the two-pH-unit rule (e.g., pH 2 for acidic analytes and pH 11 for basic analytes), achieving over 95% extraction efficiency.

Benefits and Practical Applications

• Simplified workflow reduces manual handling and solvent use compared to traditional LLE.
• Broad pH stability supports extraction of both neutral and ionizable analytes.
• Effective with challenging matrices such as viscous fluids, emulsions, and turbid samples.
• Available in multiple formats for high-throughput screening or preparative separations.

Future Trends and Potential Applications

Integration of supported liquid extraction with automated liquid handling systems and direct coupling to mass spectrometry will further enhance throughput and reproducibility. Ongoing developments in diatomaceous earth functionalization and micro-SLE formats are expected to reduce solvent consumption and support sustainable analytical practices.

Conclusion

ISOLUTE HM-N provides a robust, high-capacity supported liquid extraction solution that outperforms traditional liquid–liquid extraction. Its ease of use, wide pH range, and compatibility with automation make it a valuable asset for analytical laboratories seeking efficient sample preparation.