氢氧化镁共沉淀富集分离ICP-MS测定海水中的稀土元素

本文通过条件优化、标准验证等建立了一种直接在海水中加入NH₃·H₂O溶液使稀土元素与氢氧化镁形成共沉淀富集分离，电感耦合等离子体质谱仪测定海水中14种稀土元素的方法。海水样品通过共沉淀、离心操作后，主要基体物质得到了分离，目标稀土元素实现了富集。氢氧化镁共沉淀富集的条件是1:1 NH₃·H₂O溶液最佳加入量为0.35 mL，沉淀清洗次数为1次，静置时间为5 min。方法对稀土元素的加标回收率为88.7%~107.1%，稀土元素的方法空白为0.008×10-12 ~0.441×10-12，方法定量下限为0.054×10-12~0.423×10-12，RSD为2.8%~8.6%。所建立的方法与海水标准物质NASS-6的测定结果一致，方法具有准确度与精密度高、操作简便快速等优点，可用于大批量海水样品中稀土元素的定量精确测定。

Determination of trace rare earth elements in seawater by ICP-MS with Mg(OH)2 co-precipitation treatment

Herein, through optimization of measurement conditions and standard verification, a method for the analyzing 14 rare earth elements in sea water with inductively coupled plasma mass spectrometry(ICP-MS)was developed, by adding NH₃·H₂O directly into the seawater to form Mg(OH)₂ co-precipitation.After the co-precipitation and centrifugation operation, the main matrix materials were separated, and the enrichment of the target rare earth elements was achieved.The optimum conditions for the co-precipitation of magnesium hydroxide were as follows:0.35 mL of 1:1 NH₃·H₂O solution added in seawater as precipitation matrix, cleaning the precipitation one time for matrix separation and 5 min of the deposition time.The recoveries of the method were in the range of 88.7%~107.1%; the method blanks of 14 kinds of rare earth elements covered 0.008×10-12~0.441×10-12, the method quantitative limits were of 0.054×10-12~0.423×10-12 and the relative standard deviations (RSDs) 2.8%~8.6%.The result of NASS-6 analysis by applying this method was in good agreement with the literature report.The method is of high accuracy, good precision and simple operation, which well meets the requirement for determination of rare earth elements in seawater in large quantities.