测试项目：Nd同位素比值分析

测试对象：岩石、土壤、沉积物、海水、地下水

测试周期：45-90个工作日，可提供样品测试加急服务。

送样要求：

完成标准：前处理在超净室100级超净台内进行，保证监测空白及样品无污染，标样和重复样在允许误差范围内。
标样数据：

方法描述：
11.1全岩Nd同位素比值分析
全岩Nd同位素前处理和测试由武汉上谱分析科技有限责任公司完成。
前处理流程：
化学分离：通过Sr分离流程获得的REE溶液经过介质转换后，直接上柱分离。柱子填充LN树脂。用0.18M HCl淋洗去除基体元素。最终用0.3M HCl将Nd从柱上洗脱并收集。收集的Nd溶液蒸干后等待上机测试。
仪器测试流程：
Nd同位素分析采用德国Thermo Fisher Scientific 公司的MC-ICP-MS（Neptune Plus）。仪器配备9个法拉第杯接收器。¹⁴²Nd⁺、¹⁴³Nd⁺、¹⁴⁴Nd⁺、¹⁴⁵Nd⁺、¹⁴⁶Nd⁺、¹⁴⁷Sm⁺、¹⁴⁸Nd⁺、¹⁴⁹Sm⁺、¹⁵⁰Nd⁺同时被L4、L3、L2、L1、C、H1、H2、H3、H4等9个接收器接收。其中¹⁴⁷Sm⁺被用于监控并校正Sm对Nd同位素的同质异位素干扰。MC-ICP-MS采用了H+S锥组合和干泵以提高仪器灵敏度。根据样品中的Nd含量，50 µl/min-100 µl/min两种微量雾化器被选择使用。Alfa公司的Nd单元素溶液被用于优化仪器操作参数。Nd标准物质（GSB 04-3258-2015，200 µg/L）的¹⁴²Nd信号一般高于2.5 V。数据采集由10个blocks组成，每个block含8个cycles，每个cycle为4.194秒。Nd同位素的仪器质量分馏采用内标指数法则校正（Russell et al. 1978）：

公式中i和j指示同位素质量数，R_m和R_T分别代表样品的测试比值和参考值（推荐值），f指仪器质量分馏因子。¹⁴⁶Nd /¹⁴⁴Nd被用于计算Nd的质量分馏因子（0.7219，Lin et al. 2016）。由于前期有效的样品分离富集处理，干扰元素Sm被分离干净。残留的¹⁴⁴Sm⁺干扰校正采用Lin et al.（2016）校正方法。实验流程采用两个Nd同位素标样（GSB 04-3258-2015 和AlfaNd）之间插入7个样品进行分析。全部分析数据采用专业同位素数据处理软件“Iso-Compass”进行数据处理（Zhang et al., 2020）。GSB 04-3258-2015的¹⁴³Nd /¹⁴⁴Nd分析测试值为0.512440±6（2SD, n=31）与推荐值0.512438±6（2SD）（Li et al., 2017）在误差范围内一致，表明本仪器的稳定性和校正策略的可靠性满足高精度的Nd同位素分析。
BCR-2（玄武岩）和RGM-2（流纹岩）（USGS）被选择作为流程监控标样。两个样品分别代表了基性岩和酸性岩，具有显著的物理化学差异。BCR-2和RGM-2具有适中的Nd含量（28.7 µg/g和19 µg/g）。BCR-2的¹⁴³Nd /¹⁴⁴Nd分析测试值为0.512641±11（2SD, n=82），与推荐值0.512638±15（Wei et al. 2006）在误差范围内一致。RGM-2的¹⁴³Nd /¹⁴⁴Nd分析测试值为0.512804±12（2SD, n=80），与推荐值0.512803±10（Li et al. 2012）在误差范围内一致。数据表明，本实验流程可以对样品进行有效分离，分析准确度和精密度满足高精度的Nd同位素分析。
本测试方法适用Nd含量>3 ppm的岩石样品，保证实际地质样品测试内精度（2SE）=0.000005-0.000025（0.01‰~0.05‰，2RSE），测试准确度优于0.000025（~0.05‰），视样品Nd含量而定。Nd含量低于3 ppm的岩石样品，测试内精度和准确度会受到影响，影响程度受样品Nd含量控制。低Nd样品分析请事先咨询技术人员，确保样品分析质量。
11.2 Scheme for Nd isotope ratio analyses using MC-ICP-MS
All chemical preparations were performed on class 100 work benches within a class 1000 over-pressured clean laboratory. Column chemistry: The REE solution from the Sr-column method was evaporated to incipient dryness, and taken up with 0.18 M HCl. The converted REE solution was loaded into an ion-exchange column packed with LN resin. After complete draining of the sample solution, columns were rinsed with 0.18 M HCl to remove undesirable matrix elements. Finally, the Nd fraction was eluted using 0.3 M HCl and gently evaporated to dryness prior to mass-spectrometric measurement.
Nd isotope analyses were performed on a Neptune Plus MC-ICP-MS (Thermo Fisher Scientific, Dreieich, Germany) at the Wuhan Sample Solution Analytical Technology Co., Ltd, Hubei, China. The Neptune Plus, a double focusing MC-ICP- MS, was equipped with seven fixed electron multiplier ICs, and nine Faraday cups fitted with 10¹¹ Ω resistors. The faraday collector configuration of the mass system was composed of an array from L4 to H4 to monitor ¹⁴²Nd⁺、¹⁴³Nd⁺、¹⁴⁴Nd⁺、¹⁴⁵Nd⁺、¹⁴⁶Nd⁺、¹⁴⁷Sm⁺、¹⁴⁸Nd⁺、¹⁴⁹Sm⁺、¹⁵⁰Nd⁺. The large dry interface pump (120 m³ hr^-1 pumping speed) and newly designed H skimmer cone and  the standard sample cone were used to increase the instrumental sensitivity. Nd single element solution from Alfa (Alfa Aesar, Karlsruhe, Germany) was used to optimize instrument operating parameters. An aliquot of the standard solution of 200 μg L⁻¹ GSB 04-3258-2015 was used regularly for uating the reproducibility and accuracy of the instrument. Typically, the signal intensities of ¹⁴²Nd⁺ in GSB 04-3258-2015 were > ~2.5 V. The Nd isotopic data were acquired in the static mode at low resolution. The routine data acquisition consisted of ten blocks of 10 cycles (4.194 s integration time per cycle). The total time of one measurement lasted about 7 min.
The exponential law, which initially was developed for TIMS measurement (Russell et al. 1978) ａnd remains the most widely accepted and utilized with MC-ICP-MS, was used to assess the instrumental mass discrimination in this study. Mass discrimination correction was carried out via internal normalization to a ¹⁴⁶Nd /¹⁴⁴Nd ratio of 0.7219 (Lin et al. 2016). The interference elements Sm have been completely separated by the exchange resin process. The remaining interferences of ¹⁴⁴Sm⁺ were corrected based on the mothed described by Lin et al. (2016). All data reduction for the MC-ICP-MS analysis of Nd isotope ratios was conducted using “Iso-Compass” software (Zhang et al. 2020). One GSB 04-3258-2015 standard was measured every seven samples analyzed. Analyses of the GSB 04-3258-2015 standard yielded ¹⁴³Nd /¹⁴⁴Nd ratio of 0.512440±6（2SD, n=31）, which is identical within error to their published values (0.512438±6（2SD）Li et al., 2017). In addition, the USGS reference materials BCR-2 (basalt) and RGM-2 (rhyolite) yielded results of 0.512641±11（2SD, n=82） ａnd 0.512804±12（2SD, n=80） for ¹⁴³Nd/¹⁴⁴Nd, respectively, which is identical within error to their published values (Wei et al. 2006；Li et al. 2012).
References
Li, C. F., Li, X. H., Li, Q. L., Guo, J. H., & Yang, Y. H. (2012). Rapid and precise determination of sr and nd isotopic ratios in geological samples from the same filament loading by thermal ionization mass spectrometry employing a single-step separation scheme. Analytica Chimica Acta, 727 (10), 54-60.
Lin J., Liu Y.S., Yang Y.H., Hu Z.C. (2016). Calibration and correction of LA-ICP-MS and LA-MC-ICP-MS analyses for element contents and isotopic ratios. Solid Earth Sciences, 1, 5–27.
Russell, W.A., Papanastassiou, D.A., Tombrello, T.A., (1978). Ca isotope fractionation on the earth and other solar system materials. Geochim. Cosmochim. Acta, 42 (8), 1075–1090.
Zhang W., Hu Z.C., Liu Y.S. (2020). Iso-Compass: new freeware software for isotopic data reduction of LA-MC-ICP-MS. J. Anal. At. Spectrom., 2020, 35, 1087–1096.
Jin Li., Suo-han Tang., Xiang-kun Zhu., Chen-xu Pan. (2017). Production and Certification of the Reference MaterialGSB 04-3258-2015 as a 143Nd/144Nd Isotope Ratio Reference. Geostand. Geoanal. Res., 2017, 41, 255-262.