取干紫菜样品2.00 g置于50 mL离心管中，加入1.00 mg·L^-1内标混合溶液100 μL，加入4 mL水浸润。再加入10 mL正己烷均质20 s，加入4.0 g无水硫酸镁、1.0 g氯化钠，涡旋混匀2 min，离心，向1 mL上清液中加入100 mg N-丙基乙二胺（PSA）和100 mg无水硫酸镁，涡旋混匀1 min，离心。取上清液采用气相色谱-质谱法测定其中16种多环芳烃（PAHs）的含量。16种PAHs的质量浓度在一定范围内与其峰面积与内标峰面积的比值呈线性关系，检出限（3S/N）为0.57~3.8 μg·kg^-1。按标准加入法进行回收试验，回收率为78.3%~109%，测定值的相对标准偏差（n=6）为1.2%~14%。

The sample (2.00 g) of the dry prophyra was placed into a 50 mL centrifuge tube, and 1.00 mg·L^-1 mixed solution (100 μL) of internal standards and 4 mL of water were added to wet the sample. And then 10 mL of n-hexane was added into the solution to homogenize for 20 s, and 4.0 g of anhydrous magnesium sulfate and 1.0 g of sodium chloride were added into the solution and the mixture was vortexed for 2 min. After centrifugation, 100 mg of N-propylethylenediamine (PSA) and 100 mg of anhydrous magnesium sulfate were added into 1 mL of the supernatant and the mixture was vortexed for 1 min. After centrifugation, 16 PHAs in the superanatant were determined by gas chromatography-mass spectrometry (GC-MS). Linear relationships between the ratio of the peak area of 16 PAHs to that of the internal standard and mass concentration of PAHs were obtained in definite ranges, with detection limits (3S/N) of 0.57-3.8 μg·kg^-1. Test for recovery was made by standard addition method, giving results in the range of 78.3%-109%, and values of RSDs (n=6) were in the range of 1.2%-14%.