Quick Determination of Rare Earth Elements in Geological Samples with Open Acid Digestion or High-pressure Closed Digestion by Inductively Coupled Plasma-Mass Spectrometry

Common pretreatment such as alkali fusion,open acid digestion and microwave digestion are unsuitable for the determination of rare earth elements (REEs) in geological samples. The process of the alkali fusion method is complicated. The open acid digestion system often contains 3,or even 5 kinds of acid,and the reagent consumption is large. The microwave digestion pretreatment only treats 8 to 9 samples per batch. A method with the advantages of simple pretreatment,small acid consumption and rapid determination for digestion of geological samples and determination of 15 Rare Earth Elements by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is proposed here. Seven different acid digestion methods and the pressurized acid digestion method were studied by using 59 national standard reference materials. The analysis results show that the mixed acids of H₂SO₄ and HF under open system and the pressurized acid digestion with HNO₃ and HF method dissolved the samples effectively. The accuracy and precision of the proposed method match well with the geological standard. This method also demonstrates that the results are satisfied without mathematical calibration. The H₂SO₄-HF open acid digestion is suitable for less sample weight or high Ba content samples. The pressurized acid digestion of HNO₃ and HF method with lower detection limit is good for large quantities of samples. Both methods are reliable for REEs determination without mathematical interference correction. The acid consumption is less than 6 mL and up to 300 samples per day can be analyzed.