To establish an ICP-MS method for the detection of elemental impurities in lanthanum oxide and to explore the development of the ICP-MS methodology for high-matrix samples quantitative analysis.

25 mg samples were precisely weighed and placed in a 25 mL flask. 1 mL of nitric acid and 0.25 mL of hydrochloric acid solution were added，shaken，and dissolved for approximately 1 h，then fixed with ultrapure water. Quantitative samples determination were performed using Agilent 7900 ICP-MS in He mode with the standard curve method corrected by internal standard. The atomizing gas flow rate was set at 1.05 L·min^-1，the atomizing chamber temperature was maintained at 2 ℃，the sample aspiration rate was 0.1 r·s^-1，the RF power was 1 550 W，and the sampling depth was 10 mm. The helium flow rate was 5 mL·min^-1，and the energy discrimination was 5.0 V. Based on ICH Q2 (R2) and USP 2023 <233>，a quantitative method for 25 elemental impurities was established by utilizing the recovery rate of the method. The isotope ratio of each element in the sample was investigated，the mass number of the element to be measured was selected，and the method was verified.

Based on the specific outcomes of Se and Ce，82 and 142 were chosen as the detection mass numbers to evade interference. The results demonstrated that the linear relationships of the 24 elemental impurities were excellent，the recoveries ranged from 70% to 150%，the repeatability RSDs were less than 20%，and the method satisfied the quality control requirements. Impurities such as Pb (0.152-0.201 ng·g^-1)，Cd (0.007-0.010 ng·g^-1)，Hg (0.156-0.250 ng·g^-1) were detected in numerous batches of samples，and the contents of each element were lower than the proposed standard.

The method is specific，accurate，simple，and feasible，and can furnish technical support for the elemental impurity control of lanthanum oxide. For complex and high-matrix samples，the recovery rate of standard addition is inadequate to characterize the specificity and accuracy of the method，and the isotope ratio can be utilized as a supplement to the recovery rate of standard addition.