Separation of Nd from geological samples by a single TODGA resin column for high precision Nd isotope analysis as NdO+ by TIMS
JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY(2019)
摘要
Nd can be ionized to NdO+ about 5-10 fold more efficiently than to Nd+ by thermal ionization mass spectrometry (TIMS). However, with the NdO+ method, Ce and Pr must be separated from Nd as completely as possible to reduce CeO+ and PrO+ isobaric interferences on NdO+ (e.g.(PrO+)-Pr-141-O-18 on (NdO+)-Nd-143-O-16). With previously reported methods, it is difficult to achieve an efficient Pr-Nd separation although a perfect Sm-Nd separation can be achieved. In this study, a rapid, single column scheme for the separation of Nd and Sm from geological samples, based on TODGA resins (1 mL resin bed volume, 50-100 mu m particle size), was developed. The total column separation time, including column cleaning steps, was about 8 h. With this method, not only Nd and Sm could be efficiently separated from the sample matrix, but also a perfect separation of Nd from Ce, Pr and Sm could be obtained. The recovery yield was greater than 90% for Nd and 95% for Sm. Furthermore, since only a single TODGA column separation step was involved, low procedural blanks (Sm < 5 pg; Nd < 10 pg) could be achieved. Therefore, the method is particularly useful for the separation of low levels of Nd from geological samples for isotope analysis as NdO+ by TIMS. Finally, several rock reference materials, including BCR-2, BHVO-2, BIR-1a and UB-N, with different column loads, were analyzed to verify the reliability of the chemical procedure, and the analytical results show good agreement with the recommended values for the Nd-143/Nd-144 isotopic ratios and Sm and Nd concentrations.
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