为测定土壤中铜、铅、锌、镉、铬、镍等6种重金属可提取态的含量，采集农田区土壤样品，经风干、压碎、磨细、过筛等步骤制得粒度小于2 mm的分析样品。取此样品10.00 g，加入0.01 mol·L^-1氯化钙溶液100 mL作提取剂（土液比为1：10），在密封状态下于（20±2）℃振荡提取120 min，所得悬浮液经离心分离，用带滤膜（0.45 μm）的针筒抽取溶液10 mL，加入硝酸两滴，供电感耦合等离子体质谱法分析。同时做空白试样。在质谱分析中，采用碰撞池模式，以流量4 mL·min^-1的氦气为反应气体，从而消除了大部分质谱干扰。在制作标准曲线时，采用基体匹配法并在线加入¹⁰³Rh（5.0 μg·L^-1）和¹⁸⁵Re（10 μg·L^-1）混合标准溶液作为内标，有效地解决了基体效应等非质谱干扰。结果表明：所测定的6种重金属元素的质量浓度在一定范围内与其对应的信号强度之间呈线性关系，其检出限（3s）在0.002~0.012 mg·kg^-1之间。应用此方法分析了两个标准样品（ASB-S2和ESS-EC-1）中上述6种重金属可提取态的含量，所得结果与认定值相符，测定值的相对标准偏差（n=6）在1.2%~6.8%之间。

Aiming to the determination of 6 extractable heavy metals in soil, sample of soil was collected from field of farm-region, and treated by air-drying, crushing, grinding and sieving to prepare a portion of analytical sample having sizes less than 2 mm. 10.00 g of the prepared soil sample were extracted with 100 mL of 0.01 mol·L^-1 CaCl₂ solution (keeping the soil to solution ratio of 1 to 10) in a tightly-sealed polyethylene (PE) flask at (20±2)℃ for 120 min under constant shaking. An aliquot of 10 mL of clear solution was taken from the suspension with a filtering-syringe attached with 0.45 μm filtering membrane. Two drops of conc. HNO₃ were added to the solution, and mixed well. This solution is ready for use in ICP-MS analysis. A blank solution should be prepared simultaneously by the same procedure. The mode of collision cell with He gas at a flow-rate of 4 mL·min^-1 as reacting gas was used in MS, to eliminate most of the mass spectral interferences, and mixed standard solution of ¹⁰³Rh (5.0 μg·L^-1) and ¹⁸⁵Re (10 μg·L^-1) was added to overcome non-MS interferences, such as matrix effect and etc. Linear relationships were obtained between values of the signal intensities and the respective mass concentrations of the 6 heavy metal elements, values of detection limit (3s) were found in the range of 0.002-0.012 mg·kg^-1. Two standard samples (ASB-S2 and ESS-EC-1) were analyzed by the proposed method, giving values of extractable contents of the 6 heavy metals in consistency with the certified values, and values of RSDs (n=6) found were in the range of 1.2%-6.8%.