Abstract:A novel sampling probe composed of a coaxial-tube that functions at a continuous-flow was used to inject 1 μL of sample into an inductively coupled plasma mass spectrometer. Simply touching a sample to the dome of liquid at the inlet of the liquid microjunction (LMJ) allows for sample introduction into a flowing carrier stream that transports sample into the plasma-similar to the mechanism of sample transport in flow injection analysis. This self-cleaning sampling system, allows for sampling of minute amounts of liquids at atmospheric pressure as well as leaching of soluble components off the surface of a solid. Preliminary results demonstrate the implementation of this probe in steady-state, flow injection, and surface sampling modes. A substantial reduction of matrix effects and oxide interferences resulted with 1 μL injections. In fact, the performance of LMJ with 1 μL injections in terms of spectroscopic and non-spectroscopic interference mitigation, sensitivity and detection limit is very similar to that previously reported with 1 μL mono-segmented flow analysis.

Abstract:The analysis of lithium isotopes in high-aluminum content samples was accompanied by significant tailing of Al on Li using the traditional single-column method regardless of using single HCl or HNO3 as eluent. This hindered the precise determination of Li isotopes and made one-step column chromatographic separation of Li in silicate rocks challenging. Additional column procedures may be required to separate Li from Al in high Al samples, which would be time-consuming and result in reagent waste. In this study, the use of a 10 mL 0.2 mol L-1 HF and 0.5 mol L-1 HCl mixed eluent significantly reduced the Al tailing to less than 1% of that observed with the traditional method. The proposed purification procedure is applicable to a wide range of geological samples or minerals (e.g., silicates, seawater, sediments, and feldspars). Additionally, the matrix effect of Al and the Li concentration effect were investigated for accurate Li isotope analysis. The concentration effect, which was proved mainly led by the inappropriate treatment of the baseline. The real concentration effect yielded only a bias of 0.2‰ if normalized the solution of 20 ng g-1 Li with that of 140 ng g-1. In accounting for this, Li isotopes can now be analyzed quite accurately at variable concentrations during non-strictly concentration-matched conditions. The long-term external precision of δ7Li based on the international standard LSVEC was approximately ±0.2‰ (2SD), making it suitable for geological sample analyses. The proposed method was confirmed through the analysis of BCR-2, BHVO-2, AGV-2, BIR-1a, RGM-2, JF-1, SCo-1, GSP-2, GSR-6, and GSR-8. All the results agreed with previously published values. Besides, two in-house Li isotope solution standards CAGS-Li-P (6.25±0.25‰) and CAGS-Li-N (-15.02±0.18‰) were developed and routinely analyzed to monitor the instrumental mass bias.

Abstract:Atomization of three volatile germanium species including germanium hydride (GeH4) and its two methyl-substituted analogues – monomethyl germanium hydride (CH3GeH3) and dimethyl germanium hydride ((CH3)2GeH2) for their detection by atomic absorption spectrometry after hydride generation was comprehensively investigated. Three types of hydride atomizers based on diffusion flame (DF), multiple microflame quartz tube atomizer (MMQTA) and dielectric barrier discharge (DBD) were optimized for atomization of Ge species. In MMQTA, the supply of air and the use of gas phase dryer are the crucial parameters affecting the sensitivity. The presence of the dryer is essential also for DBD atomizer. Sensitivity was quantified under optimized conditions reaching around 2 ms ng-1 Ge in DF and 3 ms ng-1 Ge in MMQTA atomizers, respectively. The highest sensitivity of 10 ms ng-1 Ge was observed in DBD. When compared to other hydride forming elements the sensitivity observed for Ge species is two orders of magnitude worse in MMQTA, 10-50 times lower in DBD and 5 times worse in DF. In given atomizer type, the sensitivity is comparable for all three Ge species indicating the same atomization efficiency. The fraction of Ge deposited in the DBD and MMQTA atomizers, respectively, after atomization of GeH4 was quantified to 80%. Fast decay of free Ge atoms and their deposition at the inner walls of the atomizer might explain low sensitivity observed for Ge determination by atomic absorption spectrometry. Effect of L-Cysteine (L-Cys) addition to liquid standards on response of Ge species was also investigated.

Abstract:Molybdenum, nickel, and chromium play important roles in steel property. Laser-induced breakdown spectroscopy (LIBS) assisted with laser-induced fluorescence (LIF) is a promising technique with high sensitivity to elemental analyses. However, the spectra suffered from strong and unstable background from laser scattering when determining these three elements in steel matrix, which would deteriorate the accuracy. In this work, a self-adaptive method based on discrete wavelet transform (DWT) was introduced to solve this problem. No manual or subjective intervention is needed even if changing spectral ranges and elemental species. The LIBS-LIF spectral data were decomposed by Daubechies wavelet with the wavelet function db7 and the decomposition level 7. Then the spectra were reconstituted with background removal. In quantitative analyses, R squares in calibration curves of chromium, nickel, and molybdenum were greatly increased from 0.976, 0.965, and 0.981 to 0.995, 0.993, and 0.997, respectively; and the root-mean-square errors of cross-validation (RMSECVs) were significantly decreased from 0.0153, 0.0290, and 0.0152 wt.% to 0.00649, 0.00832, and 0.00793 wt.%, respectively. The results demonstrated both calibration model accuracy and analytical accuracy were greatly improved. This work provides an effective and convenient approach for modifying LIBS-LIF analyses in determination of molybdenum, nickel, and chromium in steels.

Abstract:Currently, the social stock and scrappage of printers are both huge. The waste toner collected from the ink cartridges is difficult to degrade and has a small particle size, so the common treatment method is landfill, resulting in environmental pollution and resource wastage. This research aims to exploit the abundant presence of carbon black and magnetic powder in waste toner to synthesize nitrogen and oxygen co-doped magnetic carbon materials. It speculates that the amidation reaction between with the amino group of L-cysteine and the carboxylate group of waste toner in mild one-pot conditions leads to the incorporation of nitrogen and oxygen atoms. It significantly enhances the hydrophilicity of waste toner reducing the contact angle from 138.1° to 41.0° and provides active sites for the adsorption of Pb(II). Building upon this material, a novel approach combining magnetic solid-phase extraction with graphite furnace atomic absorption spectrometry has been developed for ultrasensitive lead analysis. This method demonstrates the detection limit of 43 ng L-1 with an RSD of 7.1% (CPb(II) = 0.2 μg L-1) and has been successfully employed for the analysis of trace lead in tap water, lake water, urine, and serum. Furthermore, this material exhibits rapid adsorption kinetics, robust resistance to matrix interferences, and low cost, thereby offering a novel avenue for mitigating environmental contamination through the concept of "waste-to-waste" treatment.

Abstract:Laser ablation is a crucial process in many types of laser-matter interactions. Therefore, an accurate simulation of the laser ablation is beneficial to understanding the underlying physics in those interaction dynamics. Laser ablation simulation essentially depends on the numerical solution of heat conduction equations, usually based on finite difference strategy. Common finite difference methods include forward-Euler, backward-Euler and Crank-Nicolson schemes, corresponding to three specific finite-difference weight factors, i.e. 0, 1, and 0.5. This study proposes a new method based on an optimal weight factor, which is not a fixed value but pertinently searched for each specific problem. Taking the temporal evolution of a one-dimensional temperature field as an example, we have demonstrated that utilizing the achieved optimal weight factor can yield significantly higher accuracy than using the routine weight factors. The results in this study have the potential to better understand the heat conduction dynamics and the laser ablation physics, and hence improve the performance of relevant LMI-based techniques in the future.

Abstract:We demonstrate the capability of simultaneous measurement of 147Sm/144Nd and 143Nd/144Nd ratios in natural geological samples by MC-ICP-MS after one stage chemical purification with TODGA resin as a potential alternative to the isotope dilution method. After sample digestion, one-step chemical isolation of Sm and Nd with almost 100% recovery from sample matrix elements was accomplished by using the TODGA extraction chromatography resin. The 147Sm/144Nd and 143Nd/144Nd ratios were simultaneously determined through a single analytical session utilizing MC-ICP-MS. The present analytical protocol relies on the mathematical correction of isobaric interference, thus alleviating the separation of Nd and Sm from each other and utilizing enriched tracers. The feasibility of the present protocol was investigated by the reduplicate analyses of internationally certified reference materials (CRMs), which encompassed a wide range of chemical compositions and were of a similar order as those obtained through the isotope dilution method. This also reduced the cost and time consumption of both chemical preparation and mass spectrometric measurements.

Abstract:Calcium carbide is an important chemical raw material, and its gas evolution volume is a crucial indicator for its quality. However, the traditional methods to determine the gas evolution volume are costly and complicated. More important, it cannot be quantitatively detected with an in-situ real-time way. Herein, a totally new method to measure the gas evolution volume of calcium carbide based on Laser-induced breakdown spectroscopy (LIBS) is proposed for the first time. Tableting and pre-pulse were used to reduce the matrix effect. Moreover, the spectral pretreatments and standardization are necessary, including the removal of abnormal spectra, fitting and correction of background baselines and optimization of characteristic spectral line. Eventually, based on the principal component analysis combined with partial least squares method (PCA-PLS), a prediction model was successfully established, with the root mean square error of prediction set (RMSEP) of 1.498 L/kg. The average relative error of prediction set (AREP) is 0.48%. Our result illustrates that the LIBS provides a new solution for the rapid, accurate, and safe determination of gas evolution volume of calcium carbide.

Abstract:The chemical composition of LaNi5 needed to be measured rapidly and sensitively to control the hydrogen storage capability of the material. Glow discharge mass spectrometry (GDMS) was an excellent candidate for the measurement of LaNi5 due to its high sensitivity, simple preparation, and the capabilities of simultaneous analysis of multiple elements as well as direct analysis of solids. In practice, the application of GDMS to LaNi5 analysis was constrained by the difficulties in sample preparation arising from the morphology of LaNi5 and by the lack of the matrix-matched materials. Herein, an analytical method for the determination of 25 impurities elements in high-pure LaNi5 particles was established using GDMS. The zirconia mortar was selected as the tool for grinding the sample into powders by comparing the hardness and the introduced contaminants to those of other mortars. Under the optimized instrumental parameters, a set of relative sensitive factors (RSF) for calibration was established using nickel matrix based certified reference material, which was the analog of the matrix-matched material of LaNi5. This assumption was validated using corresponding standards with the relative error below 30% between the measured and the certified values. The previously reported universal RSFs (X. Wei, et al. Spectrochim. Acta, Part B, 2019, 154, 43–49.) were adopted for the absent elements in the available nickel standards. With this protocol, up to 25 impurity elements in LaNi5 were quantified, and the results were further validated by the other independent methods. Our work established a rapid and sensitive GDMS method for the quantitative measurement of 25 concerned impurities in LaNi5, improving the LaNi5 material analysis contents and efficiency. This method might also be applied to the sample preparation and the generation of RSFs of target element for the other complex analytes.

Abstract:This paper reviews the use of inductively coupled plasma mass spectrometry (ICP-MS) for sulfur analyses, covering articles published between January 2015 and April 2023. The ICP-MS instruments reported in the articles were classified as quadrupole ICP-MS, tandem quadrupole ICP-MS, high resolution ICP-MS, and multi-collector ICP-MS, each accounting for over 20% of the articles. Each type of ICP-MS instrument achieved detection limits < 1.0 ng/g. Laser ablation and chromatography hyphenated ICP-MS accounted for > 30% of the articles, with special attention paid to direct/imaging and speciation analyses. The leading research field in sulfur analysis is geology, followed by biology, environment, food/feed, and energy. Determination of sulfur concentrations, chemical speciation analysis of sulfur compounds, and sulfur isotope analysis accounted for approximately 30–40% of the articles. The most frequently measured sulfur isotope was 32S, followed by 34S and 33S, whereas one article reported the measurement of 36S. Selected topics of sulfur analysis using ICP-MS in research fields, hyphenated instruments, and typical applications are also introduced.