Improved Sample Pretreatment Using Offine Supercritical Fluid Extraction

Importance of the Topic

The accurate and efficient extraction of analytes from solid and complex matrices is a critical step in separation techniques such as HPLC, SFC and GC. Conventional dissolution and Soxhlet methods suffer from limitations in sample solubility, long processing times, high solvent consumption and limited automation. Supercritical fluid extraction (SFE) using CO₂ overcomes many of these drawbacks by combining liquid-like solvating power with gas-like diffusivity and permeability. Its mild operating conditions, low environmental impact and potential for full automation make SFE a powerful pretreatment approach in industrial and research laboratories.

Objectives and Study Overview

This report presents the design and application of the Nexera UC SFE pretreatment system for offline supercritical CO₂ extraction. Key goals include demonstrating how the system enables high-throughput, reproducible extractions of fat-soluble vitamins and pesticide residues in food matrices, while minimizing solvent use and manual labor. Performance metrics such as recovery, repeatability and ease of integration with downstream analysis (SFC, GC/MS/MS) are evaluated.

Methodology and Instrumentation Used

The Nexera UC SFE pretreatment system supports automated offline extraction of up to 48 samples. Core operations include:

• Sample Loading and Temperature Control – Solid samples (0.2–5 mL extraction vessels) are transferred by a rack changer into the SFE unit and heated to 40–80 °C.
• Static Extraction – Supercritical CO₂ (with optional modifiers such as methanol or ethanol) is introduced and held under pressure (7.38–15 MPa) for a defined incubation time, promoting analyte solubilization.
• Dynamic Extraction – Continuous CO₂ flow displaces the dissolved analytes into a downstream trap column (e.g., ODS), following pressure regulation and CO₂ evaporation.
• Elution and Recovery – The trap column is eluted with an organic solvent (hexane or acetone/hexane mixtures) and collection is automated via a fraction collector.

Additional sample pretreatment strategies such as dehydration agents for high-moisture samples and freeze-crushing for polymers are incorporated to optimize extraction efficiency for polar or ionic analytes.

Main Results and Discussion

1. Vitamin E Extraction from Soft-Capsule Supplement

• Sample – d-α-tocopherol in commercial soft capsule mixed with dehydrating agent.
• Conditions – CO₂ flow 5 mL/min at 40 °C and 15 MPa; 15 min static/dynamic extraction; hexane elution.
• Performance – Six replicate extractions yielded an average concentration of 0.773 mg/mL and recovery of 104 % with RSD of 1.55 %, demonstrating high reproducibility.

2. Pesticide Residue Analysis in Brown Rice

• Sample – Powdered rice blended with drying agent; spiked with 100 ng/g pesticide standards.
• Conditions – CO₂/methanol (modifier) flow 5 mL/min at 40 °C and 15 MPa; 8 min static/dynamic cycle; acetone/hexane elution; GC/MS/MS analysis in MRM mode.
• Performance – Among 301 studied pesticides, representative compounds such as cyhalofop-butyl and malathion showed recoveries of 90–93 % and RSDs below 5 %, highlighting the method’s robustness.

Benefits and Practical Applications

• High-throughput automation – processing up to 48 samples in a single run
• Reduced solvent consumption and waste compared to traditional extraction
• Excellent analyte recovery and low variability across diverse compound classes
• Mild conditions preserving labile or thermally sensitive analytes
• Seamless integration with SFC, GC/MS and LC/MS workflows for comprehensive analysis

Future Trends and Opportunities

Advancements in SFE technology may include online coupling with chromatographic systems, expanded use of green modifiers, and the development of tailored extraction protocols for highly polar and ionic targets. Integration with real-time monitoring and artificial intelligence-driven method optimization could further enhance throughput and reproducibility. Applications are expected to grow in pharmaceuticals, food safety, environmental monitoring and metabolomics.

Conclusion

The Nexera UC SFE pretreatment system provides a versatile, automated solution for efficient extraction of analytes from solid matrices. By leveraging the unique properties of supercritical CO₂, it achieves rapid, high-yield sample preparation with minimal solvent use and excellent reproducibility, supporting a wide range of analytical workflows in research and industrial laboratories.