土壤及蔬菜中微量汞的同位素稀释电感耦合等离子体质谱测定

Determination of Trace Mercury in Vegetable-growing Soil and Vegetable by Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

建立了微波消解电感耦合等离子体质谱同位素稀释(ID/ICP-MS)测定微量汞的方法。考察了仪器参数及测量条件对汞同位素比值RHg(202Hg/200Hg)测量的影响,根据同位素比值测量误差的传递因子优化了富集同位素稀释剂(202Hg>98%)的加入量,并以铊同位素比值(205Tl/203Tl)作为RHg(202Hg/200Hg)测量时发生质量歧视效应的校正因子;通过反同位素稀释法标定了富集汞同位素稀释剂的浓度。利用所建立的ID/ICP-MS方法测定了杨树叶(GBW07604)和湖积物(GBW07423)2种标准参考物中汞的含量,回收率分别为112%和100%。该方法具有准确度高、精密度好等优点,且样品前处理简便,适用于土壤及蔬菜等样品中微量及痕量汞的准确测定。

A method using isotope dilution inductively coupled plasma mass spectrometry （ID/ICP- MS） for the determination of trace Hg in vegetable-growing soil and vegetable samples was estab- lished. The concentrations of Hg in soil and vegetable were calculated with ID formula based on the accurate measurement of isotope ratio RHs（202Hg/200Hg） with ICPMS. Instrumental parameters, a- mounts of spike isotopic reagent（202Hg 〉98% ）, mass bias, dead time, and isobaric and polyatom- ic interferences were discussed and optimized. An internal standard containing 50 μg/L of T1 was simultaneously measured for the correction of mass bias and the signal fluctuation by the isotope ratio of 205T1/203T1. Concentration of the spike isotopic reagent （202 Hg） was accurately measured with the method of reverse phase isotope dilution. After being digested with HNO3 and HC104 by microwave, the concentrations of Hg in poplar leaves （ GBW07604 ） and soil （ GBW07423 ） were measured with the established method. The recoveries of 112% for poplar leaves and 100% for soil were obtained. The established method showed the advantages of simple sample preparation, good accuracy and precision, and was suitable for the determination of trace Hg in soil and vegetable.