Determination of 16 polycyclic aromatic hydrocarbons in seaweed by ultrasound-assisted gas-liquid microextraction coupled with gas chromatography-mass spectrometry

The increasing demand for the detection of polycyclic aromatic hydrocarbons（PAHs） in the complex matrices of the marine environment requires overcoming the limitations of traditional detection methods， particularly in terms of sensitivity and accuracy. Analyzing PAHs in seaweed matrices is often hindered by significant interference owing to the complex compositions of these matrices， which compromises both qualitative identification and quantitative determination. To address these challenges， this study developed an innovative and efficient method for detecting PAHs based on ultrasound-assisted gas-liquid microextraction（UA-GLME） coupled with gas chromatography-mass spectrometry（GC-MS）. The developed method involves extracting a seaweed sample with dichloromethane-hexane（DCM-HEX）（1∶1， v/v）， followed by further GLME. The separated sample is then analyzed using a DB-5MS capillary column（30 m×0.25 mm×0.25 µm） in SCAN and selective ion monitoring（SIM） modes. PAH extraction efficiencies were enhanced while significantly minimizing the co-extraction of interfering compounds by exploiting the cavitation effects of ultrasound. This optimization procedure improves both PAH-detection sensitivity and accuracy while reducing matrix effects. Under optimal conditions， the PAHs showed excellent linearity in the range of 5.0-2 000 ng/mL， with correlation coefficients（<italic>R</italic>²） exceeding 0.999. Limits of detection（LODs） ranged between 0.001 and 0.01 μg/mL， while method detection limits（MDLs） of 0.004–0.04 mg/kg were recorded. The recovery rates at high， medium， and low concentration levels were 62.32%-91.64%， with relative standard deviations（RSDs） between 2.94% and 9.15%. The developed method significantly reduces interference from lipophilic and low-volatility co-extractives， while removing co-extractives， such as long-chain alkanes， fatty acids， and sterols， at rates of up to 100%. Chromatographic comparisons revealed that the UA-GLME method delivers superior peak shapes for the target PAHs， enhanced signal-to-noise ratios， high quantitative accuracies， and remarkable resistance to seaweed-matrix interference. The method was used to detect PAHs in seaweed samples from the East China Sea， Bohai Sea， Yellow Sea， and South China Sea， with the 16 PAHs detected at varying levels. Both low-molecular-weight PAHs（such as naphthalene， phenanthrene， and fluorene） and high-molecular-weight PAHs（such as benzo［<italic>a</italic>］pyrene and benzo［<italic>k</italic>］fluoranthene） were detected at high rates. This method offers a reliable approach for the qualitative and quantitative analysis of PAHs in seaweed， thereby providing valuable technical support for assessing marine environmental pollution and evaluating risks. The developed method can be extended to other complex matrices by optimizing the ultrasound conditions and solvent system， thereby offering new strategies for environmental monitoring and pollutant-source tracing.