A method for the determination of methylmercury ( MeHg ) and ethylmercury ( EtHg ) in aquatic products was developed using gas chromatography-mass spectrometry with stable isotope-labelled internal standard. After ultrasonication assisted hydrochloric acid extraction, MeHg and EtHg in samples were extracted into toluene under the presence of sodium chloride and then back-extracted into cysteine aqueous solution. The MeHg and EtHg were released from their complexes with cysteine by adding cupric ions, and then derived with sodium tetraphenylborate. Under the optimal chromatographic conditions, MeHgPh and EtHgPh, the resulting derivatives, were separated completely on a DB-5MS capillary column and detected by electron impact ionization mass spectrometry in the selective ion monitoring ( SIM) mode, and quantified by a stable isotope dilution method using the d3-methylmercury as internal standard. The calibration curves were linear in the range of 1-500 μg/L of MeHg and EtHg. Concentration of 0. 828 mg Hg/kg with relative standard deviation ( RSD ) of 3 . 2% ( n=6 ) was obtained for MeHg in GBW 10029 . This was in good agreement with the certified values of (0. 84±0. 03) mg Hg/kg. The average recoveries were 94%-101% and 81%-104% for MeHg and EtHg spiked in aquatic samples, with RSDs of 1. 9%-4. 7% and 3. 1%-8. 2%(n=6), respectively. The limits of detection (S/N=3) of the two targets were 0. 1-0. 3μg/kg. This method was sensitive, accurate and could meet the demand of the determination of methylmercury and ethylmercury in aquatic products.%建立了测定水产品中甲基汞和乙基汞的气相色谱质谱联用分析方法。采用6.0 mol/L HCl超声辅助提取,在NaCl存在下,提取液中甲基汞和乙基汞可被甲苯萃取,再用半胱氨酸反萃取,加入CuSO4释放出的甲基汞和乙基汞与四苯硼钠反应,生成甲基苯基汞和乙基苯基汞,经DB-5MS毛细柱分离,选择离子监测方式( SIM)质谱检测,以d3-甲基汞作为内标的稳定同位素稀释法定量。甲基汞和乙基汞标准曲线的线性范围均为1~500μg/L,国家标准参考物质(GBW 10029)6次测定的甲基汞(以汞计)平均值为0.828 mg/kg,相对标准偏差为3.2%,与证书参考值(0.84±0.03)mg/kg(以汞计)一致。鱼、虾和贝类等不同种类水产品中甲基汞和乙基汞的平均加标回收率分别为94%~101%和81%~104%,相对标准偏差在1.9%~4.7%和3.1%~8.2%范围内(n=6),样品的检出限为0.1~0.3μg/kg (S/N=3)。方法灵敏,准确,可用于水产品中甲基汞和乙基汞的测定。
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