氮,氮,氮′,氮′-四辛基-3-氧戊二酰胺色谱柱分离-电感耦合等离子体质谱法测定混合稀土氧化物中重稀土

电感耦合等离子体质谱法(ICP-MS)测定稀土元素时,轻稀土元素Ce、Nd、Sm的氧化物等复合离子严重干扰重稀土元素Tb、Dy、Ho、Er的测定,因此对混合稀土中重稀土元素进行测定前一般需要先对其分离富集。实验在样品溶解后,将N,N,N′,N′-四辛基-3-氧戊二酰胺(TODGA)用硅藻土吸附后装柱,以0.1 mol/L HNO₃为样品溶液介质上柱,通过控制洗脱液的种类、酸度以及洗脱液流速,实现了轻稀土元素La、Ce、Pr、Nd与重稀土元素Tb、Dy、Ho、Er、Tm、Yb、Lu的分离和富集,建立了ICP-MS测定混合稀土氧化物中重稀土元素的方法。实验表明:控制洗脱流速为2.0 mL/min,用pH 2.0的HNO₃淋洗至淋洗体积约为500 mL,继续收集洗脱液,并用ICP-MS检测其中Nd₂O₃含量,直至洗脱液中Nd₂O₃的质量浓度小于200 ng/mL,可将轻稀土元素La、Ce、Pr、Nd及少量Y、Sm、Gd洗脱;再改用350 mL 1 mol/L HCl洗脱重稀土元素,可实现重稀土元素与La、Ce、Pr、Nd及部分Y、Sm、Gd的分离;通过选择¹⁵⁹Tb、¹⁶³Dy、¹⁶⁵Ho、¹⁶⁷Er、¹⁶⁹Tm、¹⁷²Yb、¹⁷⁵Lu为测定同位素可消除质谱干扰。将实验方法应用于混合稀土氧化物中重稀土元素的测定,加标回收率在93%～110%之间,相对标准偏差(RSD,n=8)在1.1%～10%之间。

Determination of heavy rare earths in mixed rare earth oxides by inductively coupled plasma mass spectrometry after separation with N,N,N′,N′-tetraoctyl-3-oxa-pentanediamide chromatographic column

During the determination of rare earth elements by inductively coupled plasma mass spectrometry (ICP-MS), the compound ions of oxides of light rare earths including Ce, Nd and Sm have serious interference with the determination of heavy rare earths including Tb, Dy, Ho and Er. Therefore, the heavy rare earths in mixed rare earths are usually separated and enriched before determination. N,N,N′,N′-tetraoctyldiglycolamide(TODGA) was adsorbed on diatomite then assembled to chromatographic column.After the sample was dissolved, the sample solution was immigrated on the chromatographic column with 0.1 mol/L HNO₃ as medium. The separation and enrichment of light rare earths including La, Ce, Pr and Nd from heavy rare earths including Tb, Dy, Ho, Er, Tm, Yb and Lu were realized by controlling the types, the acidity and the flow rate of eluant. Consequently, a determination method of heavy rare earths in mixed rare earth oxides by ICP-MS was established. The experimental results showed that, when the elution solution was collected and the content of Nd₂O₃ was determined by ICP-MS until the mass fraction of Nd₂O₃ in the elution was less than 200 ng/mL, the light rare earths including La, Ce, Pr, Nd and a part of Y, Sm, Gd could be eluted with HNO₃ solution at pH 2.0 until the elution volume was about 500 mL with the flow rate of eluant as 2.0 mL/min; then, the heavy rare earths were fully eluted with 350 mL of 1 mol/L HCl, realizing the separation of light rare earths (including La, Ce, Pr and Nd, and a part of Y, Sm and Gd) from heavy rare earths; the mass spectrometry interference could be eliminated by selecting ¹⁵⁹Tb, ¹⁶³Dy, ¹⁶⁵Ho, ¹⁶⁷Er, ¹⁶⁹Tm, ¹⁷²Yb and ¹⁷⁵Lu as determination isotopes. The proposed method was applied to the determination of heavy rare earth elements in mixed rare earth oxides. The recoveries were between 93% and 110%. The relative standard deviations (RSD,n=8) were between 1.1% and 10%.