Determination of chemical contaminants in marine fish by GCMS/MS using QuEChERS as an extraction method

Importance of the topic

The presence of persistent organic pollutants (POPs) in marine fish represents a significant public health concern due to their bioaccumulative nature and toxic effects. Monitoring trace levels of organochlorine pesticides, polycyclic aromatic hydrocarbons and polychlorinated biphenyls in seafood is essential for ensuring food safety, regulatory compliance and protection of consumer health.

Objectives and Study Overview

This study aimed to develop a fast, sensitive and reliable analytical method for quantifying multiple POPs in prawn samples. The goals were:

• To apply a modified QuEChERS extraction procedure for efficient cleanup of complex marine matrices.
• To employ a Shimadzu GCMS-TQ8040 triple quadrupole MS in multiple reaction monitoring mode for multi-residue detection.
• To optimize MRM transitions and collision energies using the Smart MRM optimization tool and database.
• To evaluate method performance in terms of linearity, limits of detection and quantitation, precision and recovery.

Methodology and Instrumentation

Extraction and cleanup were performed using a modified AOAC QuEChERS protocol:

• 10 g prawn tissue homogenized with 10 mL water, equilibrated 30 min.
• Extraction with 10 mL acetonitrile containing 0.5 % acetic acid and QuEChERS salts (6 g MgSO₄, 1.5 g sodium acetate).
• Centrifugation (5 min at 5000 rpm) and transfer of 6 mL supernatant to dSPE tube (1200 mg MgSO₄, 400 mg PSA, 400 mg C18).
• Vortex, centrifugation, filtration through 0.2 µm PTFE, and 2 µL injection into GCMS-TQ8040.

GC-MS/MS analysis was carried out on a Shimadzu GCMS-TQ8040 equipped with:

• Rxi-5Sil MS column (30 m × 0.25 mm, 0.25 µm film).
• Splitless injection, helium carrier gas at 1.2 mL/min, temperature program 70 °C to 280 °C.
• Electron ionization source (230 °C), interface 280 °C, MRM acquisition up to 800 transitions/sec.

MRM transitions for OCPs were imported from the Smart Database, PAHs from existing data, and PCBs optimized via Smart MRM. Collision energies were refined in Smart MRM Optimization Tool to maximize sensitivity.

Key Results and Discussion

The method produced excellent performance for a mixture of 44 POPs spiked into prawn matrix:

• Linearity over 1–50 ppb with r² ≥ 0.995.
• Limits of quantitation at 5 ppb for 90 % of analytes (10 ppb for a few compounds).
• Signal-to-noise ratios exceeding 15 at LOQ.
• Precision (%RSD) below 15 % for all targets.
• Recoveries ranging from 70 % to 130 % across compounds.

The segmented MRM method increased dwell time and sensitivity, enabling reliable trace-level quantitation in a single run of 45.9 min.

Benefits and Practical Applications

This approach demonstrates several advantages:

• Rapid multi-residue screening of pesticides and PCBs in seafood matrices.
• Elimination of multiple methods by covering 400+ analytes in one acquisition.
• High throughput with automated MRM setup and robust cleanup via QuEChERS.
• Applicability to quality control, environmental monitoring and regulatory testing.

Future Trends and Applications

Emerging developments may include:

• Integration of high-resolution MS and advanced data processing for non-target screening.
• Automation and miniaturization of sample preparation workflows.
• Application of machine learning for pattern recognition and predictive analysis of contaminant profiles.
• Expansion to other complex food and environmental matrices.

Conclusion

The combined QuEChERS extraction and Shimadzu GCMS-TQ8040 Smart MRM workflow provides a powerful solution for sensitive, accurate and efficient determination of POPs in marine fish. The method’s excellent linearity, low LOQs, good precision and high recoveries support its use for routine monitoring and risk assessment in seafood safety.

References

• Weiss J, Paepke O, Bergman A. A worldwide survey of polychlorinated dibenzo-p-dioxins, dibenzofurans, and related contaminants in butter. Ambio. 2005;34(8):22–30.
• AOAC Official Method 2007.01. Pesticide Residue in Foods by Acetonitrile Extraction and Partitioning with Magnesium Sulfate. 2007.