Separation of Nd from geological samples by a single TODGA resin column for high precision Nd isotope analysis as NdO+ by TIMS
Nd can be ionized as NdO+ about 5 10 fold more efficiently than as 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 the CeO+ and PrO+ isobaric interferences on NdO+ (e.g. 141Pr18O+ on 143Nd16O+). With previously reported methods, it is difficult to achieve an efficient PrNd separation although a perfect SmNd separation can be achieved. In this study, a rapid, single column scheme for separation of Nd and Sm from geological samples, based on TODGA resin (1 mL resin bed volume, 50-100 m particle size), was developed. The total column separation time, including column cleaning steps, was about 8 h. With this method, not only the 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 separation of low-level Nd from geological samples for isotopic 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 chemical procedure, and the analytical results show good agreements with recommended values for the 143Nd/144Nd isotopic ratios and Sm, Nd concentrations.