Abstract:

Abstract:Atom probe tomography (APT) is a cutting-edge technology capable of imaging three-dimensional atom distribution and measuring chemical composition at the sub-nano scale. Since APT samples are tip-shaped and have specific size requirements, several manufacturing methods based on focused ion beam (FIB) have been developed. In order to precisely preserve the region of interests (ROI) into the tip and also satisfy the need of correlative characterization between crystallographic information and chemical information, we developed a new approach of directly fabricating APT tips from the twin-jet electropolished transmission electron microscopy (TEM) thin disc. This method has been successfully demonstrated on a Ni-B disc sample. After its nanocrystalline structure been observed by TEM, APT tips were prepared and analyzed from the selected region of the very-edge of the center hole. The distributions of major elements from the sample itself and induced by FIB processing were also discussed. This approach exhibits universal applications, which can not only feature in the correlation between TEM and APT analysis, but also benefit for the Ga-sensitive materials as only minimum FIB processing is required.

Abstract:An air-cooling torch was developed for argon-based inductively coupled plasma mass spectrometry (ICP-MS). The plasma gas aperture-width was decreased to 0.5 mm to permit the ignition of argon plasma at an RF power of 800 W with a plasma gas of 8.0 L/min. A stable argon plasma was achieved at an RF power up to 1,600 W by introducing 20 L/min of air as cooling-gas. The signal intensity of 89Y+ obtained with the present air-cooling torch at an RF power of 1,550 W and a plasma gas of 8.0 L/min argon was around 20 % higher than that obtained with a normal torch operated at normal condition. The ratio of oxide ion (<2.0 %) for Ce with the present torch was comparable to those obtained with a normal torch. Long-term stability (over 12 h) and the service life (over one year) of the present torch were also comparable to a normal torch.

Abstract:Duplex stainless steel Z3CN20-09M serves as the predominant material for the primary pipeline within the first circuit of pressurized water reactor (PWR) nuclear power plants. Its aging grade estimation plays a crucial role in ensuring the safety of the nuclear island infrastructure. To achieve this goal, fiber-laser-based laser-induced breakdown spectroscopy (FL-LIBS) was introduced as the non-destructive and in-situ rapid detection technique for aging grade estimation. The spectral signals laser-induced plasma properties, and laser ablation processes of various Z3CN20-09M specimens with different aging grades were analyzed together with their microstructure and metallography. It was found that the spectral signal intensities of the matrix element (Fe) and the alloying element (Cr) increased with increasing aging grade, which was well explained by the increase in plasma temperature and ablation mass. Most importantly, reliable linear relationships were obtained between the signal intensity ratios of Fe Ⅱ/Fe Ⅰ, Cr Ⅱ/Cr Ⅰ, and Fe Ⅰ/Cr Ⅰ, to the aging grades, with the coefficient of determination (R2) ranging from 0.94 to 0.99. These results demonstrate that FL-LIBS is a feasible method for aging grade estimation of the Z3CN20-09M from nuclear power plants.

Abstract:Inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) has the advantage of effective separation of spectral interference. Based on ICP-MS/MS technology, a method for the determination of ultra-trace levels of titanium in bearing steel was established by investigating the effects of spectral interference elimination in different collision/reaction modes (no gas, He, H2, and O2 modes). The spectral interference from Mo++ plasma on Ti+ was eliminated using the O2 mass-shift mode. Considering the signal intensity and signal-to-background ratio of the element to be measured, the optimal O2 flow rate was determined to be 15%. 45Sc was used as an internal standard to correct the influence of instrument fluctuations, and matrix interference was eliminated using the standard addition method. Under optimized conditions, a calibration curve for titanium was established. The mass fraction was in the range of 0.0001%–0.010%, the linear correlation coefficient was greater than 0.999, and the limit of detection values of the four isotopes ranged from 0.00001% to 0.00003%. The relative standard deviation (RSD) was less than 5.0% when steel samples with three additive levels were measured six times. The recovery of titanium ranged from 90.0% to 120.0%. This method is simple to use, easy to popularize, and meets the requirements for daily analysis. In addition, the critical value of titanium in high-quality bearing steel was evaluated by calculating the uncertainty.

Abstract:Insufficiently excited plasmas generated in aqueous media with incompressibility and high thermal conductivity result in an anisotropic optical emission. The emission characteristics of underwater plasmas produced from an immersed Cu plate acquired with backward and lateral detections were investigated by irradiating with short and long pulse LIBS, respectively. We found that the plasma emission collected backward shows clear emission lines with high intensities by using long pulses, while different types of spectral lines were exhibited at different wavelengths using short pulses, including Fraunhofer-type absorption and broadened emission lines. For the lateral emission, it was unfortunately no remarkable spectral lines observed with a short pulse. By contrast, absorption lines at the resonant atomic lines of Cu and three emission lines near the wavelength of 515 nm were obtained simultaneously with a long pulse. Consequently, a weak intensity and wide line broadening occur in the spectral lines with the short pulse, while a long pulse can notably provide an enhanced line intensity and narrow line broadening. Since backward and lateral emissions exhibit significant differences, the use of long pulses allows for better observation of Fraunhofer-type absorption spectra in the lateral direction and better observation of emission spectra in the backward direction. There is a remarkable enhancement for the emission lines collected from the backward than those of the lateral direction with the line intensity being increased by more than 17 times. Therefore, a desired spectrum can be obtained by combining the lateral and backward collection methods with a long pulse. These results not only contribute to a better understanding of the radiation mechanisms in backward and lateral directions of underwater plasmas, but especially facilitate the qualitative and quantitative analysis of underwater LIBS.

Abstract:The selection of an appropriate reference material is crucial for correcting instrument-induced mass discrimination and validating B and Sr isotopic determinations in laser-ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) analyses. This study investigates the potential of a natural tourmaline as a reference material for B and Sr isotopic determinations. Major and trace element data showed that the HGL-3 tourmaline can be classified as dravite and belongs to the alkali group tourmaline. The HGL-3 tourmaline has high B contents (36830 to 43700 μg g-1), moderate Sr contents (216 to 260 μg g-1), and low Rb/Sr ratios (< 0.0013). In-situ LA-MC-ICP-MS analyses of the HGL-3 tourmaline yielded a mean δ11B value of -12.83 ± 0.38‰ (2SD, n = 485) and a mean 87Sr/86Sr ratio of 0.70835 ± 0.00019 (2SD, n = 515). These values are identical to those of powder samples determined by thermal ionization mass spectrometry (TIMS), which gave a mean δ11B value of -12.56 ± 0.24‰ (2SD, n = 6) and a mean 87Sr/86Sr ratio of 0.70833 ± 0.00004 (2SD, n = 8). The elemental and isotopic homogeneities suggest that the HGL-3 tourmaline can be used as a suitable reference material for LA-MC-ICP-MS B and Sr isotopic determinations in tourmaline.

Abstract:Three high-temperature and high-pressure sintered cassiterites doped with HfO2 were produced for use as potential reference materials for Hf isotopic analysis of cassiterite by laser ablation multi-collector inductively-coupled plasma mass spectrometry (LA-MC-ICP-MS). Ultrafine milled cassiterite powder particles (d50 = 6.3 μm) produced by wet milling were doped with HfO2 and subsequently sintered at high temperature and high-pressure to obtain homogeneous reference material for in-situ Hf isotope measurements. The sintered cassiterites have a homogeneous Hf isotopic composition at the 30 μm scale, as verified by solution nebulizer MC-ICP-MS analyses of Hf chemically separated from multiple mircodrilled sintered cassiterites, and 1065 laser ablation MC-ICP-MS analyses. The analytical results indicate a strong matrix e?ect between zircon and cassiterite during LA-MC-ICP-MS analysis. Due to low Yb and Lu contents, βHf rather than βYb was used to correct for 176Yb interference to obtain accurate 176Hf/177Hf ratios. The homogeneity of Hf isotopic compositions observed both within and between di?erent batches of sintered cassiterites suggests the potential utility of sintered cassiterite as a valuable tool for in situ isotope measurements and as an isotopic reference material.

Abstract:Respiration is an important index to evaluate the life status of organisms, thus monitoring respiration is of great significance. This study proposes a new methodology for non-invasive and real-time monitoring of organismal respiration based on laser-induced breakdown spectroscopy (LIBS). The study comprises two main components: dynamic monitoring and static analysis. In the dynamic monitoring section, LIBS is used to continuously detect and analyze multiple elements (C, H, O, and N) exhaled steadily by participants, with the carbon signal showing the closest correlation to the respiratory cycle. Fast Fourier Transform (FFT) is then applied to the carbon signal to achieve frequency domain analysis. Furthermore, it is also found that the presence of organismal respiration should be inferred from multiple element signals, rather than relying solely on the presence of carbon signal. In the static analysis, linear discriminant analysis (LDA) and backpropagation artificial neural networks (BP-ANN) are employed after LIBS measurement indicating the traceability of respiration sources is possible. This study offers a novel perspective on respiratory monitoring, demonstrating the potential of this method for real-time, convenient, and cost-effective respiration monitoring.

Abstract:The rapid and simultaneous analysis of cadmium (Cd) and mercury (Hg), as heavy metals known to be hazardous to public health, is always a challenge in complicated soil matrices. A novel solid sampling electrothermal vaporization atomic absorption spectrometry (SS-ETV-AAS) based on integrated catalytic pyrolysis technique was fabricated to develop a fast and sensitive method for the direct determination of Cd and Hg in soil. However, direct solid sampling of soil results in matrix interferences that affect the accurate analysis of Cd. In this work, modifier mixture of NaCl and citric acid (2:1 for soil: modifier) was optimized and employed to promote Cd release from soil for rapid and accurate detection, of which 30% citric acid (m:m) was added to alleviate soil coagulation at high temperatures. Under optimized conditions, the limits of detection (LODs) for Cd and Hg were 0.7 and 0.3 ng g-1 using sample size of 0.1 g. The linearity (R2) was both >0.999 and the recoveries were in the range of 81-115% with the relative standard deviation (RSD) 0.3-10.1%, showing excellent sensitivity, precision and accuracy. The complete analysis time can be controlled within ~3 min without any digestion process. The proposed method is suitable for the simultaneous detection of Cd and Hg in soil samples with features of simple, rapid and green.

Abstract:Investigating the spatial distribution of ultra-trace mercury (ng L-1) in volcanic and geothermal areas can provide insights into geological anomalies and regional volcanism. In this study, an accurate and precise method for Hg determination in geothermal water was developed using inductively coupled plasma tandem quadrupole mass spectrometry (ICP-MS/MS) and a collision/reaction cell (CRC). The experimental conditions, including the Hg isotope type and CRC gas, were optimized to eliminate severe tungsten oxide (WO) interference that occurs in conventional ICP-MS analysis of Hg. When O2 was used as the CRC gas in the MS/MS mode, the limit of quantitation (LOQ) for Hg was 0.5 ng L-1. The proposed method was successfully applied to the direct determination of Hg in a groundwater-certified reference material (ERM-CA615) and five geothermal water samples, two of which had a high W content. The satisfactory results indicate the significant potential of the proposed for determining ultra-trace levels of Hg in geological samples.

Abstract:The advent of laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) has opened new avenues for investigating iron isotope cycling across various temporal and spatial scales in biological and geological processes. However, accurate and precise measurements of iron isotopes in hematite have been hindered by the lack of matrix-matched reference materials. In this study, we developed hematite reference materials (RMs) by combining nanopowder pelletization and solid-phase sintering techniques. Nano-Fe2O3 powder was compressed into pellets and subsequently sintered at 1000°C for 120 min. This method produced stable targets with sufficient mechanical strength suitable for in-situ analysis. The prepared hematite exhibited excellent cohesion, smooth surfaces, and dense structures, making it highly suitable for laser ablation analysis. We demonstrated the homogeneity of iron isotopic composition through repeated measurements using LA-MC-ICP-MS. The δ56FeIRMM014 values for the initial powder, sintered pellets, and unsintered pellets were 0.45 ± 0.04‰ (2SD, N=20), 0.44 ± 0.04‰ (2SD, N=21), and 0.45 ± 0.02‰ (2SD, n=3), respectively, indicating high consistency. The integration of pressed powder pellet techniques with high-temperature sintering provides a rapid and convenient method for developing matrix-matched RMs. This approach shows potential for creating diverse matrix-matched reference materials for various analytical applications.