Complete sample digestion is a prerequisite for acquiring high-quality analytical results for geological samples. Closed-vessel acid digestion (bomb) has typically been used for the total digestion ...of refractory geological samples. However, the long digestion time (4–5 days) and insoluble fluoride complexes still pose challenges for digesting refractory geological samples using this approach. In this study, an efficient and simplified digestion technique combining ultrafine powders from planetary ball milling with bomb digestion was developed for trace element analysis of refractory geological samples: peridotite and granitoid. The method shows two significant improvements compared with previous approaches. (1) By performing dry planetary ultrafine milling, the initial 200 mesh peridotite (<74 μm) could be reduced to 800 mesh (<20 μm) in 6 min at a ball-to-powder mass ratio of approximately 15 using 3 mm tungsten carbide milling balls. (2) Complete peridotite and granitoid dissolution were achieved in approximately 2 h, 60 times faster than what is achievable using previous methods (2 h vs 120 h). Moreover, ultrafine powders effectively suppressed insoluble fluoride formation during bomb digestion. A suite of peridotite and granitoid reference materials were measured to evaluate the stability of this method. This efficient, simple, and reliable sample digestion method could benefit geological, food, environmental, and other fields requiring solid sample decomposition via wet acid, fusion, combustion, or dry ashing.
The gold abundance in basic rocks, which normally varies between 0.5 and 5 ppb, has served as a very important indicator in many geoscience studies, including those focused on the planetary ...differentiation, redistribution of elements during the crustal process, and ore genesis. However, because gold is a monoisotopic element that exhibits a nugget effect, it is very difficult to quantify its ultra-low levels in rocks, which significantly limits our understanding of the origin of gold and its circulation between the Earth crust, mantle, and core. In this work, we summarize various sample digestion and combined preconcentration methods for the determination of gold amounts in rocks. They include fire assay, fire assay combined with Te coprecipitation and instrumental neutron activation analysis (INAA) or laser ablation inductively coupled plasma mass spectrometry, fusion combined with Te coprecipitation and anion exchange resins, dry chlorination, wet acid digestion combined with precipitation, ion exchange resins, solvent extraction, polyurethane foam, extraction chromatography, novel solid adsorbents, and direct determination by INAA. In addition, the faced challenges and future perspectives in this field are discussed.
Stable isotope chemical labeling methods have been widely used for high‐throughput mass spectrometry (MS)‐based quantitative proteomics in biological and clinical applications. However, the existing ...methods are far from meeting the requirements for high sensitivity detection. In the present study, a novel isobaric stable isotope N‐phosphorylation labeling (iSIPL) strategy was developed for quantitative proteome analysis. The tryptic peptides were selectively labeled with iSIPL tag to generate the novel reporter ions containing phosphoramidate P−N bond with high intensities under lower collision energies. iSIPL strategy are suitable for peptide sequencing and quantitative analysis with high sensitivity and accuracy even for samples of limited quantity. Furthermore, iSIPL coupled with affinity purification and mass spectrometry was applied to measure the dynamics of cyclin dependent kinase 9 (CDK9) interactomes during transactivation of the HIV‐1 provirus. The interaction of CDK9 with PARP13 was found to significantly decrease during Tat‐induced activation of HIV‐1 gene transcription, suggesting the effectiveness of iSIPL strategy in dynamic analysis of protein‐protein interaction in vivo. More than that, the proposed iSIPL strategy would facilitate large‐scale accurate quantitative proteomics by increasing multiplexing capability.
A novel isobaric phosphorus reagent enables the accurate quantitative proteome analysis and peptide sequencing with high sensitivity. The reporter ion clusters with characteristic P−N bonds were efficiently generated with very high intensities for protein quantification.
We developed a fusion glass disc technique using small-size samples (30 mg) for assaying precious siliceous samples of geochemical reference materials using wavelength-dispersive X-ray fluorescence ...determination of major (SiO
2
, TiO
2
, Al
2
O
3
, TFe
2
O
3
, MnO, MgO, CaO, Na
2
O, K
2
O, and P
2
O
5
) and minor (Ni, Sr, and Zr) elements. The normal-size glass discs (approximately 30 mm in diameter) were prepared using an automatic fluxer, combined with manual preparation, with a flux to sample ratio of 100 : 1. GSR-1 and GSR-3 were selected to evaluate the results obtained using XRF, ICP-OES (fusion), and ICP-OES (acid attack) and to assess the accuracy and precision of the three methods based on Whitty-Léveillé and coworkers' protocol. In the present work, a set of 46 rock certified reference materials (CRMs) was used to calibrate the spectrometer and another set of 16 CRMs was analyzed further to validate the accuracy and precision of the procedure. The homogeneity of the discs was evaluated using the μ-XRF mapping image technique. In general, we obtained good agreement with the recommended values for most determinations. Finally, we summarized the small-size sample methods published in recent years and compared the advantages and disadvantages of these methods in detail.
This paper proposed a semi-automated small sample (30 mg) preparation method. The accuracy and precision of this new method were verified by measuring two CRMs among XRF, ICP-OES (fusion), and ICP-OES (acid attack) tools.
Accurate analysis using a simple and rapid procedure is always the most important pursuit of analytical chemists. In this study, a new sample preparation procedure, namely the shaker cup (SH) method, ...was designed and compared with two sample preparation procedures, commonly used in the laboratory, from three aspects: homogeneity of the sample–flux mixture, potential for sample contamination, and sample preparation time. For the three methods, a set of 54 certified reference materials (CRMs) was used to establish the calibration curves, while another set of 19 CRMs was measured to validate the results. In the calibration procedures, the matrix effects were corrected using the theoretical alpha coefficient method combined with the experimental coefficient method. The data of the major oxides (SiO2, TiO2, Al2O3, TFe2O3, MnO, MgO, CaO, Na2O, K2O, and P2O5) and minor elements (Cr, Cu, Ba, Ni, Sr, V, Zr, and Zn) obtained by wavelength dispersive X-ray fluorescence spectroscopy (WD-XRF) were compared using two derivative equations based on the findings by Laurence Whitty-Léveillé. The results revealed that the WD-XRF measured values using the SH method best agreed with the values recommended in the literature.
We developed an online continuous‐flow spectrophotometric method for determination of ferrous iron and total iron mass fractions in various types of geological certified reference materials (CRMs) ...using a Schlenk line technique to exclude oxygen during the digestion process. The continuous‐flow technique enabled automatic, reliable and real‐time analysis, and decreased sample and reagent consumption. The Schlenk line expels air to prevent oxidation during sample digestion. Compared with traditional spectrophotometric procedures, this analytical procedure is easier, more automated and more accurate. The composition of the acid matrix and time used to dissolve the samples were carefully examined. The procedure was tested on 186 replicates of twenty‐seven rock CRMs, and the results showed good agreement with the compiled values from the literature. Based on the statistical data, the proposed procedure was found to be accurate within 0.12% m/m for ferrous iron mass fraction and 0.084% m/m for total iron mass fraction compared with the certified/recommended values. The proposed procedure is accurate, reproducible and has a high throughput (ten samples per hour).
Key Points
A semi‐automatic online flow injection analysis procedure for determination both of ferrous iron and total iron mass fraction was developed.
A Schlenk line was used to provide an inert atmosphere to prevent oxidation.
Statistical tools were used to evaluate data quality.
Models for deep derivation of ophiolitic chromite from the mantle transition zone versus magmatic crystallization at lithospheric level are now highly controversial due to the discovery of ...ultrahigh-pressure (UHP) and super-reduced (SuR) minerals in ophiolitic chromitites and the presence of silicate mineral exsolution lamellae in chromite grains. According to experimental studies, chromite grains crystallized at low-pressures cannot exsolve silicate phases because of their low contents of CaO and SiO2. However, clinopyroxene needles in chromite grains from the Stillwater Complex, which is a typical layered mafic-ultramafic intrusion crystallized at crustal level, show morphological, compositional and crystallographic features very similar to exsolution lamellae in ophiolitic chromite grains. We propose that the Stillwater clinopyroxene ‘lamellae’ represent minute melt inclusions that were attached parallel to branches of skeletal chromite where they were trapped during continued growth of the grain. This interpretation is supported by the orientations of the lamella-like clinopyroxene and the coexistence of larger clinopyroxene inclusions and apatite crystals along with the clinopyroxene needles. Another possibility is that these lamella-like minerals precipitated from melt/fluid that filled cracks in the chromite grains. Trails of tiny inclusions preserved in some healed fractures are consistent with this mechanism, but are inconsistent with the regular orientations of most of the needle-like ‘inclusions’. The presence of such features in the Stillwater chromitites raises serious questions regarding the origin and significance of silicate lamellae in ophiolitic chromite grains and the use of such features to determine the depth of crystallization.
•First report of lamella-like clinopyroxene in chromite of the Stillwater mafic-ultramafic complex.•The occurrence of amorphous grains having similar composition to clinopyroxene in chromite grains.•High-pressure conditions may not be required to form clinopyroxene ‘lamella’ in ophiolitic chromite and their host chromite.
Dating mafic igneous rocks (silica-undersaturated) is difficult for the lack of suitable minerals such as zircons (ZrSiO4) commonly found in the sialic rocks such as granites. In this regard, ...baddeleyite (ZrO2) has been long recognized as the most important mineral to serve as a geochronometer for dating silica-undersaturated igneous rocks. However, separating baddeleyite is difficult due to its small grain size, typical tabular morphology, and low abundance in samples. The standard water-based separation technique requires kilogram-sized samples and usually has a very low recovery rate. In this study, a new separation method based on the different solubilities of the minerals within HF + HCl + HNO3 reagents was developed to achieve a high recovery of baddeleyite. With ∼19 g of diabase powder, the new method recovers 150–160 baddeleyite grains of 10–100 μm length and 4–50 μm width, an order of magnitude improvement over the water-based separation method, which typically recovers 11–12 similarly sized baddeleyite grains out of the ∼19 g sample. Subsequent secondary ion mass spectrometry U–Pb analyses demonstrate that the baddeleyite grains recovered by the new separation method keep the U–Pb system closed, indicating no Pb loss during acid treatment. Thus, this new method enables the most efficient baddeleyite recovery from gram-sized rocks and is anticipated to greatly contribute to the geochronological study of silica-unsaturated mafic rocks.
•An automatic on-line method was proposed for the determination of both ferrous iron and total iron contents in monominerals.•A Schlenk line was used to provide an inert atmosphere to prevent ...oxidation of the ferrous iron during digestion.•Customized digestion vessels and heating plates were used to dissolve the samples and dilute the digestion solution in situ.
An on-line photochemical method for measuring the ferrous iron Fe(II) and total iron Fe(T) contents in monominerals is described herein. A special digestion apparatus connected with a Schlenk line was designed to exclude oxygen during sample digestion. Subsequently, a spectrophotometric flow injection analysis (FIA) system was employed to automate the determination. As a result, a facile, reliable, and accurate analytical procedure was obtained, and both the sample and reagent consumption were reduced compared with traditional spectrophotometric procedures. In addition, the concentrations of the reductant and the chromogenic agent were optimized along with the sample leaching conditions (e.g., the amounts of H2SO4 and HF). Furthermore, the method precision was assessed by comparing the obtained results with those of four geological reference materials (relative standard deviation (RSD) for Fe(II) <2.30%, RSD for Fe(T) <1.75%). Finally, the accuracy of the method was assessed for four monomineral samples using the standard addition method, with recovery percentages of 95.74–104.69% and 95.07–104.56% being obtained for Fe(II) and Fe(T), respectively.
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