Improved Sample Pretreatment Using Offline Supercritical Fluid Extraction

Importance of the Topic

Pretreatment of solid samples is a critical step in analytical workflows to isolate target constituents prior to separation analysis. Supercritical fluid extraction (SFE) leverages the unique properties of supercritical CO2—high diffusivity, low viscosity, mild operating conditions and rapid phase removal—to deliver high extraction efficiency with minimal solvent use and reduced risk of analyte degradation.

Goals and Study Overview

This work introduces the Nexera UC SFE pretreatment system for offline SFE, detailing its operational principles and demonstrating its performance in extracting fat-soluble vitamins and residual pesticides from complex samples. The study aims to evaluate extraction efficiency, repeatability and integration with downstream analytical techniques.

Methodology and Instrumentation

The SFE process employs supercritical CO2 above its critical point (31.1 °C, 7.38 MPa), optionally modified with methanol or ethanol to adjust polarity. The Nexera UC SFE system automates four main steps:

• Vessel delivery and heating to set temperature (40–80 °C)
• Static extraction under constant pressure
• Dynamic extraction through the sample vessel using a back-pressure regulator and trap column
• Elution of extracted analytes with organic solvent and fraction collection

The system accommodates up to 48 vessels (0.2–5 mL) via a rack changer, all controlled from a LabSolutions workstation. Trap columns (ODS) and fraction collectors facilitate recovery for LC/MS, GC/MS, SFC or NMR analysis.

Main Results and Discussion

• Vitamin E extraction: d-α-tocopherol from supplement capsules was recovered at 102–106 % (theoretical 0.74 mg/mL) with RSD of 1.55 % across six replicates, demonstrating high reproducibility.
• Pesticide extraction: Brown rice fortified at 100 ng/g yielded GC/MS/MS quantitation for over 300 compounds with RSD < 10 % and recoveries of 70–120 %, confirming suitability for residue analysis.

Automated sample transfer and extraction reduced labor, solvent consumption and potential human error compared to Soxhlet or manual solvent methods.

Benefits and Practical Application

• Significant reduction in organic solvent usage and waste generation.
• Efficient extraction at mild temperatures, minimizing thermal degradation of labile compounds.
• High-throughput automation of up to 48 samples improves productivity and repeatability.
• Flexible polarity range via modifier addition supports diverse analyte classes.
• Seamless integration with multiple analytical detectors allows comprehensive sample characterization.

Future Trends and Applications

• Coupling inline SFE directly to chromatographic or spectroscopic detectors for real-time analysis.
• Development of greener modifier systems and further solvent minimization strategies.
• Miniaturized SFE platforms for on-site and field testing in environmental and food safety.
• Expansion into metabolomics, lipidomics and complex matrix studies across pharmaceuticals and biological research.
• Implementation of AI-based software for intelligent optimization of extraction parameters and predictive control.

Conclusion

The Nexera UC SFE pretreatment system offers a robust, automated and eco-friendly solution for extracting target analytes from solid samples. Its high efficiency, reproducibility and compatibility with various analytical techniques make it a valuable tool for laboratories engaged in food testing, pharmaceutical quality control and environmental monitoring.