High Throughput Method for the Determination of PAHs in Seafood by QuEChERS-SBSE-GC-MS

Importance of the topic

The rapid and accurate determination of polycyclic aromatic hydrocarbons (PAHs) in seafood is critical for monitoring environmental contamination, especially following oil spills. Conventional methods are often time-consuming, limiting laboratory throughput when large numbers of samples must be assessed to protect public health and ensure safe consumption of marine products.

Objectives and study overview

This study aimed to develop and validate a high-throughput analytical workflow for the quantitation of nine priority PAHs in finfish and shellfish tissues. The method combines QuEChERS acetonitrile extraction with Stir Bar Sorptive Extraction (SBSE) cleanup and concentration, followed by thermal desorption GC-MS analysis. Key performance targets included limits of quantitation below 1 ng/g, acceptable recovery and precision, and compatibility with regulatory criteria.

Used Instrumentation

• Laboratory blender and homogenizer
• Rotamix rotator and refrigerated centrifuge
• GERSTEL Twister™ stir bars and TC-2 tube conditioner
• MPS-2 autosampler with thermal desorption unit (TDU) and CIS 4 inlet
• GC-MS system (Agilent 7890 GC coupled to 5975 MSD) with Rxi-5Sil MS column

Methodology

• Sample preparation: Homogenize 3 g of seafood tissue (or 6 g at 1:1 with water) and spike with deuterated internal standards.
• QuEChERS extraction: Add 15 mL acetonitrile and salting-out salts (6 g MgSO₄, 1.5 g sodium acetate); shake, rotate for 10 min, then centrifuge. Transfer upper ACN layer.
• SBSE cleanup: Mix 1 mL ACN extract with 4 mL 0.1 M NaHCO₃; stir with a conditioned Twister for 90 min at 1200 rpm. Rinse, dry, and load Twister into thermal desorption tubes.
• Thermal desorption GC-MS: Desorb at 300 °C, transfer analytes through CIS inlet with solvent venting, and separate on a 30 m Rxi-5Sil MS column. Acquire data in multiple SIM groups optimized for each PAH.
• Quantitation: Use relative response factors calculated from standard mixtures to determine ng/g levels in tissue.

Main results and discussion

• Linearity: Excellent over 1–250 ng/g (r² > 0.99 for all analytes) in croaker, shrimp, and oyster matrices.
• Recovery: Mean recoveries ranged from 65 % to 138 % depending on compound and matrix; average recoveries were 71–108 % across matrices.
• Precision: Relative standard deviations (RSD) typically < 15 % for fortified samples.
• Limits of quantitation: Demonstrated < 1 ng/g in all matrices, easily meeting regulatory requirements.
• SRM validation: Analysis of NIST SRM 1974b mussel tissue matched certified concentrations within ± 10 % for most PAHs.
• Throughput: Estimated at 20–40 samples per analyst per instrument per day, substantially improving turnaround compared to traditional methods.

Benefits and practical applications

• Significant reduction in solvent usage and sample-handling steps compared to liquid-liquid extraction and SPE approaches.
• Enhanced matrix cleanup and concentration via SBSE, reducing interferences and lowering detection limits.
• Scalability for high-throughput monitoring during emergencies such as oil spills.
• Applicability to a wide range of apolar contaminants (e.g., alkylated PAHs, PCBs, flame retardants) in various biological matrices.

Future trends and potential applications

• Extension of the method to additional PAHs, alkylated derivatives, and emerging contaminants in seafood and environmental matrices.
• Integration with robotic sample handling and online SBSE to further increase throughput and reproducibility.
• Coupling with high-resolution or tandem mass spectrometry for enhanced selectivity and simultaneous multi-class analysis.
• Adoption in regulatory laboratories and field-deployable platforms for rapid screening and decision making.

Conclusion

The combined QuEChERS-SBSE-GC-MS workflow provides a robust, sensitive, and high-throughput solution for quantifying PAHs in seafood tissues. It meets stringent regulatory limits, offers excellent recovery and precision, and greatly enhances sample throughput. This method stands as a practical alternative to existing protocols for routine monitoring and emergency response.

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