Determination of Polycyclic Aromatic Hydrocarbons (PAHs) and Aliphatic Hydrocarbons in Oysters by GC-MS/MS

Importance of the topic

The accurate analysis of polycyclic aromatic hydrocarbons (PAHs) and aliphatic hydrocarbons in fish tissue is essential for food safety, environmental monitoring, and forensic tracing of oil contamination events such as the Gulf of Mexico spill. Simultaneous detection of these compound classes supports rapid assessment of human health risks and pollution sources.

Objectives and study overview

This study presents Method 51991 developed by Thermo Fisher Scientific for the simultaneous quantification of 16 priority PAHs and a profile of aliphatic hydrocarbons in fish and fatty seafood. The approach aims to determine whether PAH levels exceed regulatory limits and to characterize the hydrocarbon signature of crude oil in marine biota.

Methodology and instrumentation

Sample preparation and cleanup are standardized to ensure reproducible recoveries and minimal interference.

• Homogenize 2 g fish, fortify with isotopically labeled internal standards.
• Saponification in methanolic KOH at 60 °C for 30 min.
• Liquid–liquid extraction: two 100 mL hexane extractions, each followed by MeOH/water washing.
• Concentrate combined hexane extracts and perform SPE cleanup on silica cartridges.
• Evaporate eluate and reconstitute in cyclohexane with injection standard.
• GC–MS/MS analysis: full-scan for aliphatic fingerprint (m/z 45–650) and scheduled SRM for PAHs.

Instrumentation used

• Thermo Scientific TSQ Quantum XLS triple quadrupole mass spectrometer
• Thermo Scientific TRACE GC Ultra system with TR-50MS capillary column (30 m×0.25 mm, 0.25 µm film)
• Ultrasonic bath, rotary evaporator, vortex mixer, SPE manifold, precision balances

Main results and discussion

Validation experiments demonstrated average recoveries of 58–113% for the 16 PAHs, with limits of detection between 1 and 7 ng/g. Analysis of FAPAS® smoked fish and NIST crude oil spikes confirmed method accuracy and specificity. The aliphatic profile obtained by full-scan MS enabled source apportionment by matching diagnostic n-alkane distributions and isoprenoid ratios. Observed variations highlight potential alterations due to biodegradation and selective bioaccumulation in fish.

Benefits and practical applications

The method provides food safety laboratories and environmental monitoring agencies with a robust tool for regulatory compliance, risk assessment, and forensic investigation of oil contamination in seafood matrices. Simultaneous PAH quantification and hydrocarbon fingerprinting reduce analysis time and resource use.

Future trends and opportunities

• Automation of sample preparation and SPE workflows to increase throughput.
• Extension to oxygenated and alkylated PAH derivatives for more comprehensive screening.
• High-resolution mass spectrometry integration for non-targeted pollutant detection.
• Development of portable GC-MS platforms for in-field rapid screening.

Conclusion

Method 51991 demonstrates a sensitive, specific, and validated approach for simultaneous determination of PAHs and aliphatic hydrocarbons in fish, supporting food safety and environmental forensic applications.