针对四极杆ICP-MS法无法测定高纯稀土中的痕量杂质铁元素的问题，建立了电感耦合等离子体串联质谱（ICP-MS/MS）分析方法。采用氧气反应池的串联质谱技术，经优化仪器参数，确定O₂流量为2.0 mL/min，基体进样浓度为3.00 g/L，以内标In校正；同时，选择丰度为91.68%的同位素⁵⁶Fe⁺离子为分析目标，并计算出八级杆偏置负压V_oct=-10 eV时产生的质心碰撞能量E_cm高于⁵⁶Fe¹⁶O⁺反应焓ΔHr的3倍，提供的动能可确保利用O₂碰撞反应与⁵⁶Fe⁺生成目标产物⁵⁶Fe¹⁶O⁺；再设置Q₁=56/Q₂=72，有效克服⁴⁰Ar¹⁶O⁺、⁴⁰Ca¹⁶O⁺、³⁷Cl¹⁸OH⁺等多原子离子的质谱干扰，并准确测定了15种高纯稀土氧化物以及Ce、Nd、Y、Pr-Nd 4种高纯稀土中痕量杂质Fe的含量。在选定的分析条件下，校准曲线的线性相关系数大于0.9999，方法检出限（L₀）为68 μg/g，精密度（RSD，n=11）为2.1%-4.3%，回收率为95%-105%。本方法操作简便、环保，适合高纯稀土及其氧化物中痕量铁的快速测定。

Because inductively coupled plasma mass spectrometry(ICP-MS) could not be used for determination of trace Fe in high purity rare earths, an inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS) method was proposed. The mass spectral technique based on the oxygen reaction cell was used to optimize the instrument parameters, the flow rate of O₂ was adjusted to 2.0 mL/min, and the matrix injection concentration was determined to be 3.00 g/L, as well as the internal standard In was used for the calibration. Then, the isotope ⁵⁶Fe⁺ ion with abundance of 91.68% was selected as the analysis target. With Q₁=56/Q₂=72, the collision reaction of O₂ with ⁵⁶Fe⁺ was carried out to generate the target product of ⁵⁶Fe¹⁶O⁺, which performed effectively to eliminate the mass spectrum interference of polyatomic ion of ⁴⁰Ar¹⁶O⁺, ⁴⁰Ca¹⁶O⁺ and ³⁷Cl¹⁸OH⁺. So that it could accurately determine the trace impurities of Fe content in 15 kinds of high purity rare earth oxide and 4 kinds of high purity rare earth metals of cerium, neodymium, yttrium, and praseodymium-neodymium. According to the selected analysis conditions, the linear correlation coefficient of the calibration curve was greater than 0.9999, the detection limit was 68 μg/g, the relative standard deviations (RSD, n=11) were 2.1%-4.3%, and the recoveries were 95%-105%. This method is simple and environmentally friendly, and suitable for the rapid determination of trace of Fe in high purity rare earth metals and their oxides.