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High-sensitivity determination of Cd isotopes in low-Cd geological samples by double spike MC-ICP-MS
Journal of Analytical Atomic Spectrometry ( IF 3.1 ) Pub Date : 2020-01-15 , DOI: 10.1039/c9ja00397e
Decan Tan 1, 2, 3, 4, 5 , Jian-Ming Zhu 5, 6, 7, 8 , Xiangli Wang 9, 10, 11, 12, 13 , Guilin Han 5, 6, 7, 8 , Zhuo Lu 5, 6, 7, 8 , Wenpo Xu 1, 2, 3, 4, 5
Affiliation  

With new advancements in MC-ICP-MS technology, small Cd isotope fractionations in geological processes have attracted more interest in recent years. However, challenges remain in obtaining high-precision Cd isotope data for geological samples with low Cd concentrations and complex matrices. By an improved Cd purification and cleaning resin scheme for low-Cd samples using AGMP-1M resin with >90% Cd recovery, the ratios of trace elements Sn, Mo, Zr, etc. to Cd in the samples, which could potentially jeopardize the accuracy and precision of Cd isotope analysis under a high-sensitivity setup, were less than 0.001 after purification, and the total procedure blank is ≤0.1 ng. Hence, a sample containing 20–30 ng Cd can be employed for purification and subsequent isotope measurement. Cadmium isotope fractionation (expressed in δ114/110Cd relative to NIST 3108) during column separation and instrument mass bias was corrected for by a 111Cd–113Cd double spike. NIST 3108 was determined at a concentration of 5–25 ng mL−1 on a Neptune Plus (112Cd signal intensity: ∼640 V ppm−1) and 25–50 ng mL−1 on a Nu plasma III (112Cd signal intensity:∼280 V ppm−1) MC-ICP-MS equipped with an Aridus II/III desolvator for more than one year, with a total external analytical precision of 0.034‰ (2SD, n = 181). NIST SRM 2711a, NOD-P-1 and GSS-1 were measured at 5, 10, 20, 25 and 50 ng mL−1 levels to be 0.532 ± 0.038‰, 0.133 ± 0.038‰ and 0.098 ± 0.027‰, respectively, indicating that good accuracy and precision of Cd isotope analysis can be achieved with an injecting sample size as low as 5 ng Cd. Our method can be reliably applied to various geological reference materials (GRMs). The δ114/110Cd values of GRMs with relatively high and low Cd concentrations are consistent with previous studies: NOD-A-1 (0.124 ± 0.067‰), GSD-11 (−0.274 ± 0.037‰) and BCR-2 (−0.030 ± 0.063‰). SGR-1b (0.069 ± 0.049‰), GSH-1 (−0.337 ± 0.077‰) and others are reported for the first time in this paper. The δ114/110Cd in basalt and stream sediments is relatively homogeneous and overlaps with that of the bulk silicate earth (BSE). The δ114/110Cd in shale and soils varies greatly from −0.694 to 0.532‰. Human hair and other animal organs are enriched in light isotopes relative to BSE, whereas terrestrial plants are enriched in heavy isotopes.

中文翻译:

双峰MC-ICP-MS高灵敏度测定低镉地质样品中的镉同位素

随着MC-ICP-MS技术的新进展,近年来,地质过程中的小型Cd同位素分级吸引了更多的兴趣。但是,在获得低Cd浓度和复杂基质的地质样品的高精度Cd同位素数据方面仍然面临挑战。通过使用AGMP-1M树脂对Cd回收率> 90%的低Cd样品改进的Cd净化和清洁树脂方案,痕量元素Sn,Mo,Zr的比率样品中Cd的残留量可能会损害高灵敏度设置下Cd同位素分析的准确性和精密度,纯化后的Cd小于0.001,总程序空白为≤0.1ng。因此,可以将含有20–30 ng Cd的样品用于纯化和随后的同位素测量。镉同位素分馏(δ在表达110分之114柱分离和仪器质量偏差期间镉相对于NIST 3108)通过一个用于校正111 CD- 113镉双穗。在Neptune Plus上测定NIST 3108的浓度为5-25 ng mL -1112 Cd信号强度:〜640 V ppm -1),在Nu血浆III上测定的NIST 3108浓度为25-50 ng mL -1(III112 Cd信号强度:〜280 V ppm -1)配备Aridus II / III脱溶剂剂的MC-ICP-MS一年以上,总外部分析精度为0.034‰(2SD, n = 181)。NIST SRM 2711a,NOD-P-1和GSS-1的浓度分别为5、10、20、25和50 ng mL -1,分别为0.532±0.038‰,0.133±0.038‰和0.098±0.027‰,表明进样量低至5 ng Cd即可实现Cd同位素分析的良好准确性和精确性。我们的方法可以可靠地应用于各种地质参考材料(GRM)。该δ一百一十分之一百一十四Cd浓度相对较高和较低的GRM的Cd值与以前的研究一致:NOD-A-1(0.124±0.067‰),GSD-11(-0.274±0.037‰)和BCR-2(-0.030±0.063‰) 。本文首次报道了SGR-1b(0.069±0.049‰),GSH-1(-0.337±0.077‰)等。该δ 110分之114在玄武岩和流沉积物镉是相对均匀和重叠与散装硅酸盐大地(BSE)的。该δ一百一十分之一百一十四页岩和土壤中镉差异很大,从-0.694到0.532‰。相对于疯牛病,人的头发和其他动物器官富含轻同位素,而陆地植物富含重同位素。
更新日期:2020-01-15
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