吹扫捕集-气相色谱-冷原子荧光法测定大闸蟹中的甲基汞含量

Determination of methyl mercury in crabs by purge and trap gas chromatography-cold vapor atomic fluorescence spectrometry

目的建立吹扫捕集-气相色谱-冷原子荧光检测大闸蟹中甲基汞的分析方法。方法样品经过硝酸(30%,V:V)提取,采用乙基化试剂进行衍生将其转化为易挥发的甲基乙基汞,在线吹扫捕集至Tenax管,以高纯氩为载气,通过加热实现Tenax捕集管中各种形态汞的热脱附。使用气相色谱柱进行分离,在700~900℃高温下形态汞热解还原为元素汞后进入冷原子荧光检测器进行检测。结果在0.5~1000.0 pg范围内甲基汞的线性关系好,相关系数为1.000,方法的检出限和定量限分别为0.022和0.072μg/kg。在样品中分别添加1、2、5μg/kg甲基汞标准品进行加标回收率实验,平均回收率为86.8%~109.8%,相对标准偏差为1.1%~2.6%(n=6)。结论本方法具有操作简单、灵敏度高等优点,适合于大闸蟹中甲基汞的检测。

Objective To establish a method for the detection of methyl mercury in crabs by purge and trap gas chromatography-cold vapor atomic fluorescence spectrometry.Methods The samples were extracted by nitric acid(30%,V:V) and converted methyl mercury to the more volatile methylethylmercury by the ethylation derivatization,which could be concentrated through online purge and trap system with Tenax capture tube,with high purity carrier gas Ar,the thermal desorption of various forms of Hg in the Tenax trap tube was heated and methyl mercury was pyrolyzed to elemental mercury at high temperature at 700-900 ℃,then elemental mercury was detected by cold vapor atomic fluorescence spectrometer.Results The calibration curve of methyl mercury was in good linearity with a correlation coefficient of 1.000 in the range of 0.5-1000.0 pg,and the limit of detection and the limit of quantitation was 0.022 and 0.072 μg/kg respectively.While spiked at 1,2 and 5 μg/kg,the recoveries of methyl mercury ranged from 86.8%-109.8% with the relative standard deviation ranged from 1.1%-2.6%(n=6).Conclusion This method is simple,sensitive and suitable for determination of methyl mercury in crabs.