Determination of Rare Earth Elements in Sepiolite by ICP-MS Using Microwave Digestion

Nan ZHANG; Tie-min XU; Liang-ying WU; Shuang WEI; Peng-da FANG; Jia-song WANG

doi:10.15898/j.cnki.11-2131/td.201803160023

Nan ZHANG, Tie-min XU, Liang-ying WU, Shuang WEI, Peng-da FANG, Jia-song WANG. Determination of Rare Earth Elements in Sepiolite by ICP-MS Using Microwave Digestion[J]. Rock and Mineral Analysis, 2018, 37(6): 644-649. DOI: 10.15898/j.cnki.11-2131/td.201803160023

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Determination of Rare Earth Elements in Sepiolite by ICP-MS Using Microwave Digestion

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ABSTRACT

BACKGROUNDSepiolite is a fibrous hydrous magnesium rich silicate clay mineral with the content of rare earth elements between 1×10^-7 and 1×10^-5. There is no national standard method for the determination of rare earth elements in sepiolite. Determination of rare earth elements in rocks commonly uses ICP-MS. Sample pretreatments generally use closed digestion and alkaline fusion, but these two treatments are time consuming and inefficient.OBJECTIVESTo find an efficient dissolution method for the determination of 15 rare earth elements in sepiolite.METHODSBy comparing three sample pretreatment methods of nitrate hydrofluoric acid hydrogen peroxide, nitric acid-hydrofluoric acid and nitric-acid hydrogen peroxide, the nitric acid-hydrofluoric acid solution system was selected. Microwave digestion was carried out and the hydrofluoric acid was driven off to avoid the formation of insoluble fluorides from the hydrofluoric acid. The content of 15 rare earth elements was determined by ICP-MS.RESULTSDue to the high content of magnesium in sepiolite, two internal standards of ¹⁰³Rh and ¹⁸⁵Re are selected to compensate for the drift of analytical signals and to correct matrix effects. The recoveries of the method range from 91.2% to 110.9%. The detection limits are 0.002-0.011 μg/L, and the precisions are 0.81%-2.79%.CONCLUSIONSThe result of this method is in good agreement with that of the closed acid-digestion ICP-MS method, and with a small amount of acid (7 mL), high digestion efficiency (1 h), and a lower detection limit.

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Determination of Rare Earth Elements in Sepiolite by ICP-MS Using Microwave Digestion

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