Determination of Trace Rare Earth Elements in Agricultural Soils by Inductively Coupled Plasma-Mass Spectrometry

In this paper, we reported a method to determine the concentrations of 15 rare earth elements(REEs) in agricultural soils using inductively coupled plasma-mass spectrometry (ICP-MS). The influence of experimental conditions, such as sample dissolution system, preparation for standard solution, interference in mass spectrum and choice of internal standard, was evaluated. The dissolution rate of rare earth elements was improved using a mixed HNO₃-HF-H₂O₂ system to dissolve samples. 15 REEs in soil concluding yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium were determined by the said method. The online calibration of double internal standards of Rh and Re significantly reduced the effect of the signal drift on the analysis results. The detection limit of this method was 0.001 2~0.007 1 ng/mL. The actual soil samples were determined for 7 times using the recommended method, the precision and the recovery rate of which were 0.2%~4.7% and 97%~114%, respectively. The results were in good agreement with the standard value verified by National Standard Reference Materials. The method not only overcomes the deficiency of the microwave digestion method, but also can measure samples rapidly and accurately. Therefore, the method is suitable for the analysis of samples in batches.