Accelerated Solvent Extraction Techniques for In-Line Selective Removal of Interferences

Significance of the Topic

Accelerated solvent extraction with in-line cleanup addresses the challenge of co-extraction of interferences such as lipids, pigments, and other matrix constituents that compromise analyte detection and instrument performance. By integrating purification into the extraction step, laboratories can achieve faster workflows, lower solvent consumption, and improved data quality across food, environmental, and biological analyses.

Objectives and Study Overview

This technical note reviews seven accelerated solvent extraction protocols designed to remove co-extracted contaminants directly within the extraction cell. Key goals include:

• Enabling selective extraction of nonpolar analytes while retaining lipids using adsorbents such as alumina and acid-impregnated silica
• Fractionating lipid classes from biological tissues into neutral and polar fractions
• Isolating polar analytes such as perchlorate and sulfonamides using ion-exchange resins
• Applying in-cell cleanup for challenging targets like acrylamide and corticosteroids
• Combining extraction and cleanup into a single, automated workflow

Methodology and Used Instrumentation

All methods employ accelerated solvent extraction under elevated pressure (typically 1500 psi) and temperature (50 to 160 °C) with one to three static cycles. The flow-through design permits sequential use of extraction solvents and packing layers. Typical instrumentation and materials include:

• Thermo Scientific Dionex ASE 200 accelerated solvent extraction system
• Dionex ASE Prep DE cells and OnGuard ion-exchange resins
• Adsorbents: activated alumina, acid-impregnated silica gel, C18 bonded silica, Florisil, ion-exchange cartridges for Ag, Ba, H forms
• Glass-fiber and cellulose filters for cell protection

Cell preparation involves layering filters, adsorbents, and sample mixtures (often premixed with sodium sulfate or sand) before extraction. Solvent sequences vary by target, for example hexane for nonpolar cleanup followed by chloroform/methanol for polar fractions.

Main Results and Discussion

In-cell adsorption significantly reduced co-extracted lipids and pigments, producing clean extracts suitable for direct instrumental analysis:

• Alumina and acid-impregnated silica prevented lipid co-extraction in fish tissue and meal during PCB determinations
• OnGuard resins selectively retained perchlorate from vegetation using water as extraction fluid
• C18 resin facilitated sulfonamide extraction from animal tissues, with subsequent precipitation and HPLC/MS/MS analysis
• Florisil cleanup in coffee and cocoa extractions effectively removed co-extractables including acrylamide precursors
• Sequential solvent extraction allowed lipid fractionation into neutral and phospholipid classes in a single run

Optimization of solvent polarity, temperature, and adsorbent ratios was critical, for example 20–25 g alumina per gram of lipid for hexane extractions and 45.5 g acid-silica per gram of fat for nonpolar solvents.

Benefits and Practical Applications

In-cell cleanup by accelerated solvent extraction streamlines sample preparation by eliminating off-line cleanup such as gel-permeation or column chromatography. Benefits include:

• Reduced solvent usage and hazardous waste generation
• Shorter hands-on time and higher throughput
• Improved analyte recovery and reproducibility
• Compatibility with a broad range of matrices including food, environmental, and clinical samples

Future Trends and Potential Applications

Emerging directions in accelerated solvent extraction in-line cleanup include:

• Development of novel sorbent materials with tailored selectivity for emerging contaminants
• Integration with green solvent systems to minimize environmental impact
• Automated multi-dimensional extractions combining solid phase and liquid extraction steps
• Coupling directly to LC-MS/MS and GC-MS workflows for real-time method transfer
• Expanding applications to metabolomics, lipidomics, and high-throughput screening

Conclusion

The incorporation of selective adsorbents within accelerated solvent extraction cells transforms conventional workflows, enabling simultaneous extraction and cleanup. Validation across diverse analyte classes demonstrates robust performance, enhanced laboratory efficiency, and alignment with green chemistry principles. ASE with in-line cleanup stands as a versatile platform for modern analytical laboratories.

References

1. Nording M, Sporring S, Wiberg K, Bjorklund E, Haglund P. Monitoring Dioxins in Food and Feedstuffs Using Accelerated Solvent Extraction with a Novel Integrated Carbon Fractionation Cell in Combination with CAFLUX Bioassay. Anal Bioanal Chem. 2005;381:1472-1475.
2. US EPA Method 3660B. Sulfur Cleanup. EPA Cincinnati. 1996.
3. Dionex Corporation. Determination of Perchlorate in Vegetation Samples Using Accelerated Solvent Extraction and Ion Chromatography. Application Note 356; 2006.
4. Dionex Corporation. Rapid Determination of Sulfonamide Residues in Animal Tissue and Infant Food Containing Animal Products Using Accelerated Solvent Extraction. Application Note 353; 2005.
5. Bjorklund E, Muller A, von Holst C. Comparison of Fat Retainers in Accelerated Solvent Extraction for the Selective Extraction of PCBs. Anal Chem. 2001;73:4050-4053.
6. Sporring S, Bjorklund E. Selective Pressurized Liquid Extraction of Polychlorinated Biphenyls from Fat-Containing Samples. J Chromatogr A. 2004;1040:155-161.
7. Ezzell J, Richter B, Francis E. Selective Extraction of PCBs from Fish Tissue Using Accelerated Solvent Extraction. Am Environ Lab. 1996;12:12-13.
8. Dionex Corporation. Selective Extraction of PCBs from Fish Tissue Using Accelerated Solvent Extraction. Application Note 322; 1996.
9. Dionex Corporation. Determination of PCBs in Large-Volume Fish Tissue Samples Using Accelerated Solvent Extraction. Application Note 342; 2000.
10. Gomez-Ariza JL, Bujalance M, Giraldez I, Velasco A, Morales E. Determination of Polychlorinated Biphenyls in Biota Samples Using Simultaneous Pressurized Liquid Extraction and Purification. J Chromatogr A. 2002;946:209-219.
11. US EPA Method 3620C. Florisil Cleanup. EPA Cincinnati. 2000.
12. Gomez-Ariza JL, Garcia-Barrera T, Lorenzo F, Gonzales AG. Optimisation of Pressurised Liquid Extraction for Haloanisoles in Cork Stoppers. Anal Chim Acta. 2005;540:17-24.
13. Draisci R, Marchiafava C, Palleschi L, Cammarata P, Cavalli S. Accelerated Solvent Extraction and Liquid Chromatography-Tandem Mass Spectrometry Quantitation of Corticosteroid Residues in Bovine Liver. J Chromatogr B. 2001;753:217-223.
14. Gentili A, Perret D, Marchese S, Sergi M, Olmi C, Curini R. Accelerated Solvent Extraction of Confirmatory Analysis of Sulfonamide Residues in Raw Meat and Infant Foods by Liquid Chromatography Electrospray Tandem Mass Spectrometry. J Agric Food Chem. 2004;52:4614-4624.
15. Dionex Corporation. Extraction and Clean Up of Acrylamide in Complex Matrices Using Accelerated Solvent Extraction Followed by Liquid Chromatography Tandem Mass Spectrometry. Application Note 358; 2006.
16. Poerschmann J, Carlson R. New Fractionation Scheme for Lipid Classes Based on In-Cell Fractionation Using Sequential Pressurised Liquid Extraction. J Chromatogr A. 2006;1127:18-25.
17. Poerschmann J, Trommler U, Biedermann W, Truyen U, Lucker E. Sequential Pressurised Liquid Extraction to Determine Brain-Originating Fatty Acids in Meat Products as Markers in Bovine Spongiform Encephalopathy Risk Assessment Studies. J Chromatogr A. 2006;1127:26-33.