Simultaneous measurement stable and radiogenic Nd isotopic compositions by MC-ICP-MS with a single-step chromatographic extraction technique

Removing interferences such as Ce on Nd isotopes during column chemistry is hard to achieve due to their similar properties. In this study, we established a simple but efficient Nd separation technique with the perfect separation of Nd from Ce and nearly 100% Nd yield using the TODGA resin (50-100 mu m, Eichrom, USA) after actual measurements. All samples used here through the Nd separation technique have Ce/Nd ratios less than 0.003. The whole procedure takes about 10 h. The stable Nd isotopes were measured by MC-ICP-MS and calibrated with standard-sample-standard bracketing (SSB) combined Eu internal normalization. The potential influences of Eu and Ce on stable Nd isotopic analysis were strictly evaluated. The long-term analyses of the JNdi-1 standard produced a total average delta Nd-142/144 of 0.000 +/- 0.029 parts per thousand (2SD, n = 210), delta Nd-145/144 of 0.000 +/- 0.029 parts per thousand (2SD, n = 210), and delta Nd-146/144 of 0.000 +/- 0.027 parts per thousand (2SD, n = 210). Two pure Nd standards, La Jolla and Nd-GIG, produced delta Nd-146/144 values (means +/- 2SD, n = 20) of -0.227 +/- 0.030 parts per thousand and 0.226 +/- 0.021 parts per thousand, respectively. delta Nd-146/144 (means +/- 2SD, n = 20) of seven geological reference materials (BCR-1, BHVO-2, AGV-2, GSP-2, NOD-P-1, NOD-A-1, and GBW07249) were also reported. The reproducibility of delta Nd-146/144 was better than 0.030 parts per thousand. These results are in good agreement with the published DS-TIMS methods. In addition, our method also allows the concurrent determination of the radiogenic Nd-143/Nd-144 ratio. All the Nd-143/Nd-144 ratios of these samples are identical with the preferred values published in the GeoReM Database. These results indicated that the method of Nd isotopic analysis established here can simultaneously measure high-precision delta Nd-142/144, delta Nd-145/144, delta Nd-146/144, and radiogenic Nd-143/Nd-144 ratio for geological materials.

Automated summary

This study established an efficient Nd separation technique that successfully reduced interferences, allowing for stable analysis of Nd isotopes in geological samples with simultaneous high-precision measurements of various Nd isotope ratios and the radiogenic Nd-143/Nd-144 ratio.