Determination of persistent organic pollutants in fish tissues by EXTREVA ASE system and GC-MS/MS

Importance of the topic

The accumulation of persistent organic pollutants (POPs) such as PCBs, OCPs, PBDEs and PAHs in aquatic food chains poses serious risks to environmental and human health. Monitoring these contaminants in fish tissues is critical for food safety and regulatory compliance. Traditional extraction and cleanup techniques are labor-intensive, consume large solvent volumes and may co-extract matrix interferences. The development of an automated, solvent-efficient method with in-line cleanup enhances throughput, reduces waste and maintains analytical performance.

Objectives and overview

This study demonstrates a fully automated workflow for multi-residue analysis of 29 halogenated hydrocarbons (6 PCBs, 16 OCPs, 7 PBDEs) and 4 PAHs in fish tissue. Key goals include integrating accelerated solvent extraction (ASE) and in-line cleanup on the Thermo Scientific EXTREVA ASE system, evaluating method performance parameters (linearity, recovery, precision, detection limits) and applying the method to Mediterranean shad samples.

Methodology and instrumentation used

Sample preparation:

• Thirty Mediterranean shad were purchased and stored at –22 °C.
• Muscle tissue was freeze-dried, homogenized with diatomaceous earth and spiked with internal standards.
• Samples loaded in 22 mL stainless steel ASE cells with cellulose filters and Supel QuE Z-Sep sorbent for in-line lipid cleanup.

Accelerated solvent extraction and concentration:

• Thermo Scientific EXTREVA ASE system with gas-assisted hexane/acetone (4:1) extraction at 80 °C.
• Flow rate 0.5 mL/min, cell fill 70%, extract volume ~26 mL per sample.
• Evaporation to 0.5 mL at 40 °C under nitrogen and vacuum.

GC-MS/MS analysis:

• Thermo Scientific TRACE 1310 GC coupled to TSQ 8000 triple quadrupole MS.
• RXI-XLB capillary column, splitless injection, helium carrier gas.
• Electron ionization and selected reaction monitoring with two transitions per analyte.
• Data acquisition and quantification with Xcalibur and TraceFinder software.

Main results and discussion

Performance characteristics:

• Linearity over 1–50 ng/g with r² ≥ 0.99 for all compounds.
• Recoveries: 93–100% for PCBs, 93–104% PBDEs, 84–103% OCPs, 99–109% PAHs.
• Precision: RSDs between 4% and 19% (n = 6).
• Limits of detection 0.5 ng/g; limits of quantification 1 ng/g.

Application to real samples:

• All PCBs detected in 100% of fish samples (1.1–11.8 ng/g dry weight).
• PBDE 47 present in all samples; other PBDEs detected at frequencies between 30% and 80% (1.0–5.7 ng/g).
• OCP residues including DDE and DDD found in up to 70% of samples (0.8–3.0 ng/g).
• PAHs detected less frequently, with benz(α)anthracene and chrysene in up to 83% of samples; all below regulatory limits.

Method advantages:

• In-line Z-Sep sorbent improves lipid removal and system robustness.
• Freeze-drying eliminates water co-extraction and manual drying steps.
• Integrated ASE extraction and cleanup halves sample preparation time and reduces solvent use by ~40% compared to conventional methods.

Benefits and practical applications

This streamlined method offers high throughput, consistent analytical quality and minimized solvent waste. It is well suited for routine monitoring of POPs in fish and other food matrices, regulatory compliance testing, environmental surveys and quality control laboratories engaged in food safety analysis.

Future trends and application possibilities

Potential extensions include:

• Adapting the workflow for other food and environmental matrices (meat, dairy, sediments).
• Expanding target lists to emerging contaminants and metabolites.
• Coupling with high-resolution MS for non-target screening.
• Miniaturization and integration with online data processing for real-time monitoring.
• Application in large-scale surveillance programs and research on bioaccumulation.

Conclusion

The fully automated EXTREVA ASE with in-line Z-Sep cleanup coupled to GC-MS/MS provides a reliable, efficient and environmentally friendly approach for multi-class POP analysis in fish tissues. The method meets stringent performance criteria, accelerates laboratory throughput and supports comprehensive monitoring of persistent contaminants in food.

Reference

• IARC. Overall Evaluations of Carcinogenicity, Vol. 1 to 42, Suppl 7; IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans; IARC: Lyon, France, 1987.
• U.S. EPA Method 3545A: Pressurized Fluid Extraction. United States Environmental Protection Agency, 2007.
• Srinivasan K., Ullah R. Method and Device to Extract Analyte from a Sample with Gas Assistance, U.S. Patent 9,440,166 B2, 2016.
• Srinivasan K., Ullah R. Apparatus for Parallel Accelerated Solvent Extraction, U.S. Patent 11,123,655 B2, 2021.