Search

Stable nickel (Ni) isotopes have shown great potential for investigating planetary accretion processes, mantle–crust magmatism, and paleo-marine evolution. The development of an economical and time-efficient separation method for Ni isotope analysis holds significant value within the realm of Ni isotope research. Previous purification methods for Ni isotope analysis have typically relied on either multi-column procedures or the utilization of significant quantities of organic reagents, such as acetic acid, acetone, and dimethylglyoxime. In this study, a novel two-column chromatographic separation procedure was presented for the determination of Ni isotope compositions in geological materials. A cation resin (AG50W-X8) was utilized in conjunction with diluted HCl and HF to effectively remove a substantial portion of matrix elements. Subsequently, trace amounts (100–200 μL) of Ni-spec resin were used for further purification of Ni. This relatively simple purification scheme for Ni isotope analysis effectively reduces the use of organic reagents and the amount of Ni-spec resin compared to previous methods that relied on multi-column separation and organic reagent extraction. Ni isotopic compositions were analyzed using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The instrumental mass discrimination of Ni isotopic ratios was corrected for using the double spike (DS) combined with the sample–standard bracketing (SSB) method. The Ni isotope compositions (δ60Ni) of in-house standards (SCP and CUG) were −0.06 ± 0.05‰ (2 SD, n = 104) and 0.36 ± 0.06‰ (2 SD, n = 97), respectively. Furthermore, the measured δ60Ni values of various geological reference materials (BCR-2, BHVO-2, BIR-1, DTS-1, DTS-2b, SDO-1, GSP-2, and W-2a from the USGS; JB-1b from the GSJ; GSR-2, GSR-3, GSR-4, GSR-5, and GSR-10 from the NRCGA) were consistent with previous studies within measurement error. Additionally, the δ60Ni values of AGV-1 from the USGS, as well as those of GSR-10, GSR-12, GSR-15, GSR-17, GSR-18, and GSR-19 from the NRCGA are reported here for the first time. Based on repeated measurements of pure solutions and reference materials, the long-term reproducibility of δ60Ni values was better than ± 0.06‰ (2 SD). Consequently, our study presents a relatively straightforward purification method for Ni for its isotopic analysis using only trace amounts of organic reagents and Ni-spec resin. [ABSTRACT FROM AUTHOR]

In this study, a novel lithium metaborate fusion technique using a homemade fusion furnace and graphite crucibles was developed to produce homogeneous glasses from silicate rock powder. The glasses were then analyzed for both major and trace element concentrations by LA-ICP-MS. The parameters of the ratio of flux-to-sample, melting temperature and time, and closed fusion were optimized. It was found that homogeneous glasses could be obtained, and the loss of Pb was effectively suppressed at a low melting temperature and short time (900 or 950 °C for 5 min) in closed fusion. Compared to Pt or Pt–Au crucibles in the traditional flux fusion method, homemade graphite crucibles are more economical and omit the need of any releasing agent because the bottom curve design allows the melt to shrink into a bead for easy removal. Accurate results by LA-ICP-MS can be directly obtained by applying a quantitative calibration strategy using 100% oxide normalization, which offers a solution for unknown sample analysis without the prior determination of the concentration of an internal standard element. The analytical results of 42 major and trace elements in 5 USGS silicate rock reference materials (covering mafic to felsic rock types) using the developed LiBO2 fusion technique are consistent with the reference values within 10% for most elements, and analytical precision (RSD) is within 10% for most elements. The developed method is simple for preparing homogeneous glasses from rock powders, which displays great potential for the rapid and accurate determination of mass fractions of major and trace elements in silicate rocks using LA-ICP-MS. [ABSTRACT FROM AUTHOR]

Silver (Ag) is a trace metal element in geological rocks and accurate determination of its abundance is very challenging given significant oxide and hydroxide interferences from Zr, Nb, Mo, and Y. Here, we developed a valid method based on inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS), in which NH3 was used as the reaction gas, to determine the Ag content in geological samples. The additional quadrupole analyzer located in front of the collision/reaction cell ensured a simple and controllable reaction in the cell. The first quadrupole (Q1) was set to m/z 107 and 109 to allow Ag+ and its interferences to enter the reaction cell. Ag+ partially reacted with NH3, forming Ag+ and Ag(NH3)2+ as the main products; while the major interferences, ZrO+ and NbO+, reacted strongly and were converted to ZrO(NH3)4+, ZrO(NH3)5+, and NbO(NH(NH3)3)+, respectively, and thus no longer affected the measurement of Ag. Consequently, the Ag signals could be detected by both "on-mass" and "mass-shift" methods, where the m/z of Q1–Q2 were 107–107, 109–109 and 107–141, 109–143, respectively. Under the optimized NH3 flow rate (3.5 ml min−1), the interference levels of the matrix solution (0.3 μg ml−1 Zr and Mo, 0.2 μg ml−1 Zn, 0.1 μg ml−1 Y and Nb, and 0.05 μg ml−1 Ga) in four Q1–Q2 mass pairs were negligible and comparable to background signals, and the limits of detection of geological samples were <0.53 ng g−1. The Ag content of 19 geological reference materials was reported using the proposed ICP-MS/MS method, and the results were consistent with isotope dilution-ICP-MS values. Thus, the proposed method has great potential for the accurate, direct, and high-throughput measurement of Ag in geological samples. [ABSTRACT FROM AUTHOR]

We present detailed characterization of Tanz zircon megacrysts for the microbeam determination of U–Pb ages, Zr isotopes, Hf isotopes, O isotopes and trace element mass fractions. This batch of dark brown zircon megacrysts from Tanzania contains 269 ± 103 μg g−1 U (Th/U ∼ 0.154), and its total weight is 9.06 kg. The largest Tanz zircon megacryst in this batch weighs 366 grams. The calculated average accumulated alpha-radiation dosage is 0.54 × 1018 events per g for the Tanz zircon, which correlates with a 'well crystallized' structure. Through a large number of laser ablation ICP-MS, laser ablation MC-ICP-MS and SIMS measurements, it is found that Tanz zircon megacrysts are quite uniform in U–Pb ages, O isotopes and Zr isotopes at scales of tens of microns. The Tanz zircon has chemical abrasion isotope dilution TIMS (CA-ID-TIMS) determined mean isotopic ratio values of 0.09180 ± 0.00013 (2SD, n = 47) for 230Th corrected 206Pb/238U, 0.7473 ± 0.0014 (2SD, n = 47) for 207Pb/235U and 0.059069 ± 0.000067 (2SD, n = 47) for 230Th corrected 207Pb/206Pb. The CA-ID-TIMS method yielded a mean 230Th corrected 206Pb/238U age of 566.16 ± 0.77 Ma (2SD, n = 47). The determined mean δ18OVSMOW and δ94/90ZrSRM3169 values of the Tanz zircon megacrysts are 6.52 ± 0.28‰ (2SD, n = 29) and −0.01 ± 0.06‰ (2SD, n = 35) by gas source mass spectrometry and double spike TIMS, respectively. All of these values are in good agreement with the statistical mean values of microbeam measurements and are proposed as the best reference values for Tanz zircon megacrysts. These features make the Tanz zircon megacrysts suitable as primary U–Pb age and Zr–O isotope reference materials for microbeam analysis. However, our LA-MC-ICP-MS data suggest a relatively wide distribution of Hf isotope compositions in the Tanz zircons (0.281821 ± 0.000042, 2SD, n = 321), which makes Tanz zircons not an ideal Hf isotope reference material for microbeam analysis. We propose the Tanz zircon megacrysts as a potential reference material for the primary external calibration or monitoring of analytical validation for microbeam determination of U–Pb ages and Zr–O isotopes. [ABSTRACT FROM AUTHOR]

Using boron as a test analyte, laser ablation (LA) solution sampling multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) is proposed and validated as a fast method for isotopic analysis in natural liquids and digested samples without any prior purification process. We demonstrated that the solution reference standard can be used as a bracketing standard for in situ δ 11 B analysis in solids. Based on a sensitivity enhancement of 8- to 9-fold, all testing solutions were diluted in a 5% (v/v) NH 3 ·H 2 O instead of classical 2% (v/v) HNO 3 . With a discrete and minimal sample solvent loading by the LA sampling strategy, it produces nearly "dry" plasma conditions that tolerate the sample matrix remarkably. The memory effect, one of the most difficult challenges in boron analysis, was dramatically eliminated with only 15 s wash time; thus, each analysis took less than 100 s. No significant matrix effects were observed for varying 50-100% boron concentrations in the samples and varying 20-60% NH 3 ·H 2 O matrix used for the dilution, as well as for samples doped with a 1/100 synthetic seawater matrix. The external precision of δ 11 B measurements in NIST 951a was ± 0.30‰ (2SD). Good agreement with the values described in literature studies was achieved for δ 11 B measurements in eight geological reference materials, with precisions between 0.4 and 0.7‰ (2SD), confirming the accuracy of the proposed method. The proposed method offers advantages of simple sample preparation, fast analysis, and little use of chemical reagents.