取经洗净、切成小段并用四分法取样和粉碎的蔬菜样品1.000 g于PTFE消解容器中，加入硝酸7 mL在消解仪中于120℃恒温保持30 min。随后将容器移入微波消解仪中，在1 000 W功率下按设定程序消解25 min。冷却后用硝酸（2+98）溶液将消解完全的溶液定容至25.0 mL，用电感耦合等离子体质谱法测定样品中Cr、Cd、As、Pb、Hg的含量。对测定中遇到的同量异位素干扰，选取相应的原子丰度较高的同位素⁵²Cr，¹¹¹Cd，⁷⁵As，²⁰⁸Pb及²⁰²Hg作为被测元素，可在一定程序上降低此类干扰。此外，蔬菜中常含有C、H、O、N、Cl、S、Mo等元素，能与载气中的Ar结合产生多原子离子干扰。因此，在测定¹¹¹Cd，⁵²Cr，⁷⁵As时，采用DRC模式并以NH₃作为反应气可消除此类干扰。测定²⁰²Hg及²⁰⁸Pb时无此类干扰，故采用STD模式。对样品的基体干扰，采用在线内标加入法予以校正。在DRC模式下测定¹¹¹Cd，⁵²Cr及⁷⁵As时可能产生新干扰，采用设定RP_q值可排除此类干扰。试验结果表明：所测定的5种元素的质量浓度在一定范围内与各元素的分析信号强度之间呈线性关系，其检出限（3s/k）在0.2~3.2 μg·kg^-1之间。按标准加入法进行回收试验，测得回收率在92.9%~108%之间，测定值的相对标准偏差（n=5）在1.2%~5.8%之间。

Vegetable was collected from the growing area, washed with water, cut into segments and sampled by quartering; the sample was then crushed and 1.000 g of the crushed sample was treated with 7 mL of HNO₃ in a constant temperature digester at 120℃ for 30 min. The digested solution was then removed to a microwave digester to have a further digestion of the sample under 1 000 W for 25 min. After cooling, the digested solution was diluted with HNO₃ (2+98) solution and its volume was made up to 25.0 mL, which was used for ICP-MS determination of Cr, Cd, As, Pb and Hg. Isotopes having high relative abundance (i.e. ⁵²Cr, ¹¹¹Cd, ⁷⁵As, ²⁰⁸Pb and ²⁰²Hg) were selected as the species in the respective determinations to overcome effects of isobaric interferences to a definite extent. Besides, elements of C, H, O, N, Cl, S and Mo, which were existed in vegetables very often, might form polyatomic ions with Ar in the carrier gas, making interferences of polyatomic ions. DRC mode with gaseous NH₃ as reactant in the MS determinations of ¹¹¹Cd, ⁵²Cr and ⁷⁵As was adopted to eliminate such interferences. STD mode was applied to the MS determinations of ²⁰²Hg and ²⁰⁸Pb, since no polyatomic ion interference was encountered in these cases. Moreover, to overcome some new interferences arised in the DRC mode of determinations, setting up to RP_q values was found to be effective. It was shown by the testing results, linear relationships between values of intensities of analytical signals and the mass concentrations of the 5 related elements were found in the definite ranges, with their detection limits (3s/k) ranging from 0.2 to 3.2 μg·kg^-1. Recovery was tested by standard addition method, giving results of recovery in the range from 92.9% to 108%, and RSDs (n=5) in the range of 1.2%-5.8%.