Showing papers in "Journal of Analytical Atomic Spectrometry in 2015"
TL;DR: In this paper, a single particle ICP-MS (spICP-MS) was used as a screening tool for the detection and characterization of nanoparticles in complex matrices such as food and biological tissues.
Abstract: Detection and characterization of nanoparticles (NPs) in complex media as consumer products, food and toxicological test media is an essential part of understanding the potential benefits and risks of the application of nanoparticles. Single particle ICP-MS (spICP-MS) was studied as a screening tool for the detection and characterization of nanoparticles in complex matrices such as food and biological tissues. A data evaluation tool was created for the calculation of particle size, concentration and size distribution from the raw data. spICP-MS measurements were carried out on a standard quadrupole instrument as well as on a sector-field instrument. Performance characteristics were determined for four types of NPs. For the quadrupole instrument the size detection limits were 20 nm (Au and Ag), 50 (TiO2) and 200 nm (SiO2). For the sector-field instrument size detection limits are lower, 10 nm (Au). Concentration detection limits ranged from 1 ng L−1 for 60 nm Au NPs to 0.1 μg L−1 for 500 nm SiO2 particles. The dynamic range of spICP-MS is limited to two orders of magnitude and as a consequence sample dilution is often required. The precision of the method was found to be <5% and <10% for the determination of particle size and concentration, respectively while the accuracy for particle size (Au NP only) was <10%. The robustness against potential sample matrix components was investigated. The applicability to routine samples was demonstrated by four examples (food, waste water, culture media and biological tissues). The presented combination of spICP-MS measurements with a powerful data evaluation tool enables the use of this technique as a fast, cost efficient and easy to use screening tool for metal and metal oxide NPs that can be widely implemented in the statutory monitoring of food and consumer products for the presence of NPs, as well as in the analytical evaluation of toxicological studies.
182 citations
TL;DR: The challenges in processing large XRF datasets featuring several million pixels/spectra and the strategies developed to overcome them are described.
Abstract: Technical progress in the fields of X-ray sources, optics and detectors is constantly enhancing the pace of data acquisition in XRF imaging. This enlarges the size of the hyperspectral datasets and the number of their sub-parts. This paper describes the challenges in processing large XRF datasets featuring several million pixels/spectra and the strategies developed to overcome them. During the investigation of historical paintings by scanning macro-XRF the main challenges are the correct identification of all spectral features in a dataset and its timely processing. For the identification of spectral features different approaches are discussed, i.e. the use of sum spectra, maximum pixel spectra and of χr2 maps. For the time-efficient, artefact-free evaluation of XRF imaging data, different software packages are evaluated and intercompared (AXIL, PyMCA, GeoPIXE and the in-house written datamuncher). The process of data evaluation is illustrated on a large dataset (3.4 MPixels) acquired during the investigation of a version of Caravaggio's Supper at Emmaus (143 × 199.5 cm2). This 17th century painting is currently the largest object entirely scanned with macroscopic XRF.
123 citations
TL;DR: In this paper, it was shown that neither variations in the composition of zinc soaps nor fatty acids adsorbed on pigment surfaces are responsible for the second zinc carboxylate species.
Abstract: The formation of metal soaps is a major problem for oil paintings conservators. The complexes of either lead or zinc and fatty acids are the product of reactions between common pigments and the oil binder, and they are associated with many types of degradation that affect the appearance and stability of oil paint layers. Fourier transform infrared spectroscopy (FTIR) reveals that a paint sample from The Woodcutter (after Millet) by Vincent van Gogh contains two distinct zinc carboxylate species, one similar to crystalline zinc palmitate and one that is characterized by a broadened asymmetric stretch COO− band shifted to 1570–1590 cm−1. This observation has been made in many paintings. Although several hypotheses exist to explain the shifted broad carboxylate band, these were not supported by experimental evidence. In this paper, experiments were carried out to characterize the second zinc carboxylate type. It is shown that neither variations in the composition of zinc soaps (i.e. zinc soaps containing mixtures of fatty acids or metals) nor fatty acids adsorbed on pigment surfaces are responsible for the second zinc carboxylate species. X-Ray diffraction (XRD) and FTIR analysis indicate that the broad COO− band represents amorphous zinc carboxylates. These species can be interpreted as either non-crystalline zinc soaps or zinc ions bound to carboxylate moieties on the polymerized oil network, a system similar to ionomers. These findings uncover an intermediate stage of metal soap-related degradation of oil paintings, and lead the way to improved methods for the prevention and treatment of oil paint degradation.
114 citations
TL;DR: In this article, a review of recent calibration approaches and related standards preparation techniques for the analysis of various solid materials by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is presented.
Abstract: For solid sample quantitative analyses by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), the main analytical problem is the calibration step: evaluation of the function (equation) that correlates the signal with the concentration of analytes in the sample. Except for basic standards preparation, problems result from non-stoichiometric effects during vaporization, transport of ablated aerosols, atomization, and ionization in the plasma. These effects, called elemental fractionation, are mainly sample matrix dependent and thus suggest that standards used for calibration should accurately match the sample matrix. Preparation of such standards is a difficult and time-consuming process, so since the beginning of LA-ICP-MS applications for quantification of solid sample composition, different approaches have been developed to solve the problem, primarily complete matrix matching. Because the calibration of LA-ICP-MS is a key factor for its quantification capabilities, this review summarizes recent calibration approaches and related standards preparation techniques for the analysis of various solid materials by LA-ICP-MS. Selected papers concern the application of reference glasses, solution based standards, synthetic standards based on the main sample matrix component or powdered matrix certified reference materials, matrix-matched standards based on spiked sample materials, and non-matrix-matched standards, for calibration. Isotope dilution methods and signal normalization protocols used in order to improve precision are also considered.
106 citations
TL;DR: In this paper, the authors discuss the merits and limitations of presently available mass spectrometric instrumentation for international nuclear material safeguards applications and highlight the need for further improvements in TIMS, ICP-MS and SIMS performance aimed at obtaining more specific and significant isotopic information.
Abstract: Mass spectrometry is currently being implemented in a wide spectrum of research and industrial areas, such as materials science, cosmo- and geochemistry, biology and medicine, to name just a few. Research and development in nuclear safeguards is closely related to the general field of “Peace Research”, representing a specific application area for analytical sciences in general and for mass spectrometry in particular. According to Albert Einstein “peace cannot be kept by force. It only can be achieved by understanding”. Understanding implies a realistic estimation of potential challenges and threats, which is based on the ability to obtain timely, reliable and independent information. A particular task of international nuclear material safeguards is reducing threats that are posed by the proliferation of nuclear weapons. An important part of the International Atomic Energy Agency (IAEA) safeguards system is the “analytical laboratory”, with mass spectrometric techniques, such as thermal ionization mass spectrometry (TIMS), secondary ion mass spectrometry (SIMS), and inductively coupled plasma mass spectrometry (ICP-MS) belonging to the most powerful methods for the analysis of nuclear material and environmental samples collected during inspections. Each of the currently applied techniques provides definite merits (e.g. precision, accuracy, time-effectiveness, high sensitivity, spatial resolution, reduced molecular interference, etc.) for a specific safeguards related application. Thus, taking advantage of each technique helps the analyst to gain a larger quantity of safeguards-relevant information. Along with the analysis of element amounts and isotopic compositions of uranium and plutonium in nuclear material the challenging applications of mass spectrometry include isotopic analysis of micro-samples, age determination of nuclear material as well as identification and quantification of elemental and isotopic signatures of inspection samples in general. Analysis of inspection samples implies strict quality control procedures and it demands the production of suitable certified isotopic reference materials which are used as calibration standards or as quality control samples. This manuscript discusses merits and limitations of presently available mass spectrometric instrumentation for such safeguards applications. It will also highlight the need for further improvements in TIMS, ICP-MS and SIMS performance aimed at obtaining more specific and significant isotopic information.
104 citations
TL;DR: In this paper, a support vector machine (SVM) and partial least square (PLS) methods were used to perform quantitative and classification analysis of 20 slag samples, and the performance of the SVM calibration model was investigated by 5-fold cross-validation.
Abstract: The laser induced breakdown spectroscopy (LIBS) technique coupled with a support vector machine (SVM) and partial least square (PLS) methods was proposed to perform quantitative and classification analysis of 20 slag samples. The characteristic lines (Ca, Si, Al, Mg and Ti) of LIBS spectra for slag samples can be identified based on the NIST database. At first, quantitative analysis of the major components (Fe2O3, CaO, SiO2, Al2O3, MgO and TiO2) in slag samples was completed by SVM with the full spectra as the input variable, and two parameters (kernel parameter of RBF-γ and σ2) of SVM were optimized by a grid search (GS) approach based on 5-fold cross-validation (CV). The performance of the SVM calibration model was investigated by 5-fold CV, and the prediction accuracy and root mean square error (RMSE) of SVM and PLS were employed to validate the predictive ability of the multivariate SVM calibration model in slag. The SVM model can eliminate the influence of nonlinear factors due to self-absorption in the plasma and provide a better predictive result. And then, two type of slag samples (open-hearth furnace slag and high titanium slag) were identified and classified by a partial least squares-discrimination analysis (PLS-DA) method with different input variables. Sensitivity, specificity and accuracy were calculated to evaluate the classification performance of the PLS-DA model for slag samples. It has been confirmed that the LIBS technique coupled with SVM and PLS methods is a promising approach to achieve the online analysis and process control of slag and even in the metallurgy field.
100 citations
TL;DR: In this paper, the authors carried out a systematic experiment of O-isotope analyses using a Cameca IMS-1280 SIMS to quantitatively characterize the topography effect with the aim of better understanding its physical mechanism underlying such an artifact.
Abstract: The surface condition of a sample mount is an important factor influencing the precision of SIMS isotope analysis. The phenomenon that the sample topography affects the analytical precision is called the topography effect. We carried out a systematic experiment of O-isotope analyses using a Cameca IMS-1280 SIMS to quantitatively characterize the topography effect with the aim of better understanding its physical mechanism underlying such an artifact and ultimately improving the analytical precision. Our results indicate that within a mineral grain, the topography effect is obvious in the X-direction (horizontal direction) of the sample stage but insignificant in the Y-direction (vertical direction). In addition, within a single mineral grain, the topography effect creates analytical spots on the left rim (lower X-coordinates) yielding higher measured δ18O values than those on the right rim (higher X-coordinates) in our instrument. The physical reason that the topography effect compromises the analytical reproducibility is attributed to lateral energy dispersion of secondary ions caused by surface topography changing the ion position in the entrance slit plane. By increasing the transfer optics magnification, the topography effect could be significantly reduced. Beam centering parameters could be used to quantitatively assess the topography effect and improve the data quality.
95 citations
TL;DR: The Sr–Ca method was designed to accommodate a wide variety of sample types, including carbonates, bones, and teeth; silicate rocks and sediments; fresh and marine waters; and biological samples such as blood and urine.
Abstract: We present a commercially-available, fully-automated, offline chromatography method capable of simultaneously purifying both Ca and Sr for stable and radiogenic isotope analysis. The method features effective purification and mutual separation of Ca and Sr from complex matrixes using a single, highly-reusable chromatographic column. Low carryover combined with high yield for multiple extractions indicates the column can be reused for at least 200 samples. Accurate and precise stable and radiogenic isotope data are presented for BCR-2 basalt, NIST-1400 bone ash, IAPSO seawater, and an in-house llama bone standard (CUE-0001). The Sr–Ca method was designed to accommodate a wide variety of sample types, including carbonates, bones, and teeth; silicate rocks and sediments; fresh and marine waters; and biological samples such as blood and urine. The system is highly adaptable and capable of processing up to 60 samples per run at a rate of 32 samples per day on a single chromatographic column during unattended operation.
93 citations
TL;DR: In this paper, a review of the literature related to clinical and biological materials, foods and beverages, and nanomaterials is presented, focusing on exposure and absorption of nanoparticles; potential toxicity, use as reagents in analytical methods and analysis or characterisation of these materials.
Abstract: This review covers publications from the second half of 2016 to the middle of 2017. Techniques and applications relevant to clinical and biological materials, foods and beverages are discussed in the text, presenting the key aspects of the work referenced, while the tables provide a summary of the publications considered. Further to the observations made in the 2017 Update, we have noted the increase in publications featuring nanomaterials. Topics relate to exposure and absorption of nanoparticles; potential toxicity, use as reagents in analytical methods and the analysis or characterisation of these materials. A growing number of techniques are being applied to bio-imaging. In particular, those involving XRF spectrometry are being applied to a large range of biological sample types. A gradual trend during recent years, that is now quite apparent, has been the increasing proportion of publications that involve foods and beverages compared with clinical samples. Not necessarily related, but another trend is the growing number of reports from laboratories in the Republic of China.
90 citations
TL;DR: The study presented here demonstrates that LIBS–RF is a useful technique for the identification and discrimination of iron ore samples, and is promising for automatic real-time, fast, reliable, and robust measurements.
Abstract: Laser-induced breakdown spectroscopy (LIBS) integrated with random forest (RF) was developed and applied to the identification and discrimination of ten iron ore grades. The classification and recognition of the iron ore grade were completed using their chemical properties and compositions. In addition, two parameters of the RF were optimized using out-of-bag (OOB) estimation. Finally, support vector machines (SVMs) and RF machine learning methods were evaluated comparatively on their ability to predict unknown iron ore samples using models constructed from a predetermined training set. Although results show that the prediction accuracies of SVM and RF models were acceptable, RF exhibited better predictions of classification. The study presented here demonstrates that LIBS–RF is a useful technique for the identification and discrimination of iron ore samples, and is promising for automatic real-time, fast, reliable, and robust measurements.
83 citations
TL;DR: In this paper, the speciation steps (sample preparation, species speciation and detection) most commonly used for the determination of arsenic in food are described, together with some less utilised techniques.
Abstract: Arsenic is ubiquitous in nature appearing in various chemical forms. The toxicity, environmental mobility and accumulation of As in living organisms depends on the form in which the element exists, thus requiring techniques which can identify specific forms whilst retaining their integrity during extraction and pre-treatment prior to measurement. Both organic and inorganic arsenic species may be present in food staples of both terrestrial and marine origin as well as natural waters, at sub ng l−1 to high mg l−1 levels. In this review, the speciation steps (sample preparation, species speciation and detection) most commonly used for the determination of As in food are described. High performance liquid chromatography separation with plasma source mass spectrometry is often the technique of choice due to its versatility, robustness and good detection limits. However, detection systems such as atomic absorption spectroscopy, atomic fluorescence spectrometry, and atomic emission spectrometry are also widely used and covered in this review together with some less utilised techniques.
TL;DR: In this article, a comparison of different fractionation correction methods for Pb isotope measurement is presented, and the effects of sample purity and variable sample matrices on measurement precision and accuracy have been examined.
Abstract: Analytical precision for Pb isotope measurement by thermal and plasma source mass spectrometry has improved by an order of magnitude in the last 20 years. Much of this improvement relates to a shift away from the external method of correcting instrumental mass fractionation – where samples are assumed to fractionate to the same extent as an average value of a working measurement standard. Implementation of a variety of techniques, including thallium spiking, sample–standard bracketing and double/triple spiking has provided more robust methods of fractionation correction. Isotope laboratories use one or more of these procedures, but an assessment of the measurement precision and relative merits of each system is needed to determine which is the most appropriate for the purpose. This study reviews each of these methods and provides a comparison based on an extensive analytical record covering 18 years, and using a variety of mass spectrometers. As two or three of the methods have been applied to most measurements, direct and robust comparisons can be made between correction protocols. In particular the effects of sample purity and variable sample matrices on measurement precision and accuracy have been examined. Data acquired from the measurement of rock, soil and metal are used to provide a statistical comparison of the analytical uncertainty of each technique, guiding the choice of the most appropriate method. Isotope standard data acquired over this period is also compared with other high-precision laboratories to generate a set of concordant working ratios for the NIST SRM 981 Pb standard: 206Pb/204Pb = 16.9412; 207Pb/204Pb = 15.4988; 208Pb/204Pb = 36.7233.
TL;DR: In this paper, a low dispersion ablation cell and the connecting tubing achieve a 99% washout of the aerosol in ∼6 ms, enabling separated pulse responses at frequencies up to 200-300 Hz.
Abstract: Performance data are reported for a commercially available laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) setup, equipped with a custom-made cell. The low dispersion ablation cell and the connecting tubing achieve a 99% washout of the aerosol in ∼6 ms, enabling separated pulse responses at frequencies up to 200–300 Hz. In addition, the cell employed supports a post-acquisition methodology for the deconvolution of overlapping ablation positions in scanning mode by an iterative Richardson–Lucy algorithm. This enables correction of the distortion in the scan profile upon traversing layers with dimensions below the physical size of the laser beam. By overlapping the ablation positions of a 1 μm diameter laser beam, a lateral resolution in the order of 0.3 ± 0.1 μm was demonstrated for scanning of μm-sized layers in high capacitance multi-layer ceramic capacitors.
TL;DR: A review of advances in the XRF group of techniques published approximately between April 2015 and March 2016 can be found in this paper, where a bench top TXRF spectrometer for the measurement of the elements from carbon to uranium is described that offers achievable detection limits that range from ng g−1 to μg g −1.
Abstract: This review describes advances in the XRF group of techniques published approximately between April 2015 and March 2016. Fundamental contributions in the instrumentation sections include the development of synchrotron radiation sources, semiconductor design technology and evaluating the quality of in situ hand-held XRF results. A bench top TXRF spectrometer for the measurement of the elements from carbon to uranium is described that offers achievable detection limits that range from ng g−1 to μg g−1. The applications sections aim to give a representative overview of the range of applications that use XRF techniques with an emphasis on papers that describe technical or application innovation. Sample size investigated ranged from the planet Mercury down to nano-gram quantities of cement secreted by settlement stage barnacle larvae. The archaeological and cultural heritage section this year includes an authentic report on the use of cannabis as a filler in ancient lime plaster and heartening news that the construction of an underground parking garage in the centre of Zurich (Switzerland) unearthed the remains of seven Neolithic settlements from the 4th and 3rd millennium BC. The X-ray excitation of iron present in ancient iron-gall inks was presented as a step toward the non-invasive reading of fragile and/or unopenable documents. Feedback from readers of this review is most welcome and the review coordinator may be contacted using the email address provided.
TL;DR: A switchable solvent-based liquid phase microextraction (SS-LPME) procedure has been established for the preconcentration of copper prior to its determination by microsampling flame atomic absorption spectrometry (FAAS).
Abstract: A switchable solvent-based liquid phase microextraction (SS-LPME) procedure has been established for the preconcentration of copper prior to its determination by microsampling flame atomic absorption spectrometry (FAAS). Triethylamine (TEA) was adopted for the study as a green and cheap switchable solvent. The Cu(II)-1-(2-pyridylazo)-2-naphthol (PAN) complex was extracted into the TEA phase by converting the protonated carbonate (P-TEA-C) to TEA. The experimental conditions have been comprehensively studied and optimized. The limit of detection (LOD) and repeatability (RSD%) of the method were 1.80 μg L−1 and 3.8%, respectively, and its accuracy was assessed against certified reference materials (TMDA-64.2 fortified water, TMDA-53.3 fortified water, TMDA-51.3 fortified water, 1573a tomato leaves, INCT-OBTL-5 oriental basma tobacco leaves and NCS ZC 8100 2b human hair), and by addition-recovery tests. The SS-LPME-FAAS method was also applied for the determination of trace amounts of copper in water, food and hair samples.
TL;DR: In this paper, an in-house developed method based on Asymmetric Flow Field Flow fractionation-Inductively Coupled Plasma Mass Spectrometry (AF4-ICP-MS) for the simultaneous detection and quantification of citrate-stabilised silver nanoparticles (AgNPs) in water, has been applied to realworld liquid antimicrobial consumer products based on colloidal silver.
Abstract: In 2011 the European Commission published its recommendation for a definition for the term nanomaterial which requires the materials to be characterized in terms of the number size distribution of their constituent particles. More recently, the definition has begun to be applied to the labelling of food and cosmetic products where any components present in the form of engineered nanomaterials must now be clearly indicated in the list of ingredients. The implementation of this definition requires that methods be developed and validated to accurately size particles with at least one external dimension in the range of 1–100 nm, and to quantify them on a ‘number-based’ particle size distribution. An in-house developed method based on Asymmetric Flow Field Flow Fractionation-Inductively Coupled Plasma Mass Spectrometry (AF4-ICP-MS) for the simultaneous detection and quantification of citrate-stabilised silver nanoparticles (AgNPs) in water, has been applied to real-world liquid antimicrobial consumer products based on colloidal silver. This transfer of the method from ideal model systems to real products was assessed in light of other techniques including Centrifugal Liquid Sedimentation (CLS), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). Five out of six analysed products were found to contain AgNPs in the nano-range by means of a number of techniques including AF4-ICP-MS. Comparative analysis shows that CLS has sufficient size resolution to size AgNPs in the consumer products while DLS was unsuccessful probably due to sample polydispersivity. Despite the silver nanoparticles having unknown surface properties and stabilisation agents which could have influenced the sizing with AF4, a relatively good agreement between TEM and AF4-ICP-MS was observed. The AF4-ICP-MS data could be converted from mass-based to number-based distributions; this transformation, despite the possibility of experimental artefacts being mathematically amplified, has shown promising results.
TL;DR: In this paper, a high precision method to measure Ba isotopes by MC-ICP-MS was presented, where Barium is separated from matrices by using a cation exchange resin (AG50W-X12, 200-400 mesh).
Abstract: We present a high precision method to measure Ba isotopes by multiple-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). Barium is separated from matrices by using a cation exchange resin (AG50W-X12, 200–400 mesh). Instrumental mass bias of Ba isotopes was corrected by a sample-standard bracketing method using SRM3104a as the bracketing standard. Potential effects of different matrices from resin and samples, and acid molarity and concentration mismatch were rigorously evaluated in this study. The precision and accuracy of this method were tested by the measurement of a synthetic solution made by mixing SRM3104a Ba with other matrix elements. The average δ137/134Ba of the synthetic solution is −0.005 ± 0.047‰ (2SD, n = 36) relative to SRM3104a. The robustness of this method was further assessed by replicated analyses of 8 reference materials, including igneous rocks with mafic to felsic compositions. The δ137/134Ba of basalt standards BCR-2, BHVO-2, and JB-2 is 0.050 ± 0.039‰ (2SD, n = 13), 0.047 ± 0.028‰ (2SD, n = 22), and 0.085 ± 0.035‰ (2SD, n = 19), respectively; diabase standard W-2 is 0.035 ± 0.022‰ (2SD, n = 11); andesite standard AGV-1 is 0.047 ± 0.040‰ (2SD, n = 11) and JA-2 is 0.038 ± 0.048‰ (2SD, n = 17); rhyolite standard RGM-1 is 0.142 ± 0.030‰ (2SD, n = 15); and granodiorite standard GSP-2 is 0.013 ± 0.046‰ (2SD, n = 15). Two late Mesozoic basalts from China have a δ137/134Ba of −0.132 ± 0.020‰ (2SD, n = 7) and 0.001 ± 0.034‰ (2SD, n = 7), respectively. Based on repeated analyses of the synthetic standard and a carbonate standard IAEA-CO-9, the long-term external precision of our method is better than ±0.05‰, much smaller than the variation of δ137/134Ba in these reference standards and samples (up to 0.27‰). Therefore, the Ba isotopic composition can be used as a novel tracer to study geochemical processes.
TL;DR: In this paper, a combustion-trapping dual-stage protocol was proposed for preconcentration of Hg from a PM sample collected on a quartz fiber membrane (QFM) for high-precision Hg isotopic analysis.
Abstract: The Hg isotopic signature may provide insight into tracking the sources and pathways of both airborne particulate matter (PM) and particle-bound Hg (PHg) in the atmosphere. However, separating and concentrating trace levels of PHg and accurately analyzing its isotope ratios remain a technical challenge. Here, we optimized a combustion-trapping dual-stage protocol specifically for the pre-concentration of Hg from a PM sample collected on a quartz fiber membrane (QFM) for high-precision Hg isotopic analysis. The protocol was validated by testing synthetic samples of varying concentrations and trapping solutions of different volumes, and by comparison with two conventional methods (acid digestion and column purification). Using the dual-stage protocol, an individual sample containing up to 570 ng of Hg can be combusted at programmed temperatures in an Hg-free O2 stream, and the volatilized gaseous Hg was trapped in a 5 mL acid (4 M HNO3 and 1.3 M HCl) mixture. The method results in a relatively lower procedural blank and quantitative recovery (99 ± 6%, 2SD, n = 90). Long-term measurements of three certified reference materials (CRM021, CRM024, and GBW07405) with complex matrices using the optimized protocol gave identical Hg isotopic ratios of both mass-dependent fractionation (MDF) and mass-independent fractionation (MIF), in agreement with the results obtained from the standard addition method. The protocol was applied to two PM2.5 samples collected on a 20.3 × 12.5 cm QFM. The result showed evident variations of both MDF and MIF, highlighting the importance of studying Hg isotopic compositions in PM of variable environments in order to fully understand the behaviors of Hg and its isotopes in the atmosphere.
TL;DR: In this article, femtosecond-Laser Induced Breakdown Spectroscopy (fs-LIBS) is introduced for 3D chemical analysis of Li-ion solid state electrolytes in electrochemical energy storage systems.
Abstract: Direct chemical imaging is critical to understand and control processes that affect the performance and safety of Li-ion batteries. In this work, femtosecond-Laser Induced Breakdown Spectroscopy (fs-LIBS) is introduced for 3D chemical analysis of Li-ion solid state electrolytes in electrochemical energy storage systems. Spatially resolved chemical maps of major and minor elements in solid-state electrolyte Li7La3Zr2O12 (LLZO) samples are presented, with a depth resolution of 700 nm. We implement newly-developed visualization techniques to chemically image the atomic ratio distributions in a LLZO solid state electrolyte matrix. Statistical analysis, 2D layer-by-layer analysis, 2D cross-sectional imaging and 3D reconstruction of atomic ratios are demonstrated for electrolyte samples prepared under different processing conditions. These results explain the differences in the physical properties of the samples not revealed by conventional characterization techniques, and demonstrate the ability of fs-LIBS for direct 3D elemental imaging of Li-ion battery solid-state electrolytes.
TL;DR: In this article, the contribution of incomplete particle vaporization to the deviation from the linearity of the ICP-MS intensity is estimated using a mathematical model of particle vaporisation.
Abstract: We have identified incomplete particle vaporization and non-linear detector response as the major factors that cause the non-linearity of SP-ICP-MS measurements at high particle mass. The contribution of incomplete vaporization to the deviation from the linearity of the ICP-MS intensity is estimated using a mathematical model of particle vaporization. The non-linear detector response in the pulse-counting mode is due to the overlapping of the analyte ions at the detector within the 40 ns dead time of the electron multiplier. The overlap can be severe because of the relatively short pulse duration of 300 μs of the ion plumes of the discrete sample particles. The non-linear detector response has been modeled using Poisson statistics. We have also examined the applicability of calibration methods based on the standard particles, discrete standard solution droplets, and continuous nebulization of standard solution. The standard-solution calibration method requires linear calibration curves. The method may also suffer from errors due to the difference in the sensitivity of the standard solution and sample particles. Calibration using standard particles and discrete standard solution droplets do not have these limitations.
TL;DR: In this article, Synchrotron radiation (SR) micro-X-ray fluorescence (μ-XRF) reveals that after photo-degradation, various oxidation and migration processes take place.
Abstract: Realgar and orpiment, arsenic sulfide pigments used in historic paints, degrade under the influence of light, resulting in transparent, whitish, friable and/or crumbling paints. So far, para-realgar and arsenic trioxide have been identified as the main oxidation products of arsenic sulfide pigments. This paper shows that after photo-degradation, various oxidation and migration processes take place. Synchrotron radiation (SR) micro-X-ray fluorescence (μ-XRF) reveals arsenic to be distributed throughout the whole multi-layered paint system. Arsenic (As) K-edge micro-X-ray absorption near edge structure (μ-XANES) analyses indicate the presence of an intact AsxSy pigment, arsenite compounds (As3+; As2O3), and arsenate compounds (As5+); the latter are certainly present as calcium, lead, aluminium and iron arsenates. Sulfur (S) K-edge μ-XANES points to the conversion of the sulfide (S2−) group to a sulfate (SO42−) group, probably via an elemental sulfur (S0) or sulfoxide (S2+) compound. Principal Component Analysis (PCA) and subsequent k-means clustering of multi-energy SR μ-XRF maps and μ-XANES were performed to identify the various arsenic species and visualize their distribution. The arsenates (As5+) are spread throughout the entire paint system and dominate the photo-degraded paint and ground layers, while the arsenite compounds (As3+) are located close to the intact arsenic sulfide pigment. The oxidation of arsenic trioxide into arsenates likely takes place in aqueous solutions. The presence of As5+ compounds in the paint systems indicates that the arsenic trioxide is dissolved by ambient water present in the paint. Arsenite and arsenate compounds are water soluble and are transported by water throughout the paint system. This knowledge is crucial for the conservation field, as this is the first time that (indirect) evidence of water transport within paintings has been given.
TL;DR: Analysis by collision cell ICP-MS significantly over-estimated As and Se concentration due to REE doubly charged formation; mathematical correction increased the accuracy of analysis but is prone to error when analyte concentration and sensitivity is low and interferent is high.
Abstract: Recent reports of As concentrations in certain food and drinks have garnered public concern and led to a lowering of the US guideline maximum concentration for inorganic As in apple juice and proposed limits for As in rice products. In contrast Se is an essential micro-nutrient that can be limiting when Se-poor soils yield Se-poor food crops. Rare earth element (REE) doubly charged interferences on As and Se can be significant even when initial ICP-MS tuning minimizes doubly charged formation. We analyzed NIST 1547 (peach leaves) and 1515 (apple leaves), which contain high levels of REEs, by quadrupole ICP-MS with (He) collision mode, H2 reaction mode or triple quadrupole ICP-MS (ICP-QQQ) in mass-shift mode (O2 and O2/H2). Analysis by collision cell ICP-MS significantly over-estimated As and Se concentration due to REE doubly charged formation; mathematical correction increased the accuracy of analysis but is prone to error when analyte concentration and sensitivity is low and interferent is high. For Se, H2 reaction mode was effective in suppressing Gd2+ leading to accurate determination of Se in both SRMs without the need for mathematical correction. ICP-QQQ using mass-shift mode for As+ from m/z 75 to AsO+ at m/z 91 and Se+ from m/z 78 to SeO+ at m/z 94 alleviated doubly charged effects and resulted in accurate determination of As and Se in both SRMs without the need for correction equations. Zr and Mo isobars at 91 and 94 were shown to be effectively rejected by the MS/MS capability of the ICP-QQQ.
TL;DR: In this article, the effects of three different cone combinations and the addition of N2 with the guard electrode, either grounded or floating, on the performance of Nd isotope analyses were investigated.
Abstract: To improve the precision and accuracy of in situ Nd isotope analyses in geological samples, high analytical sensitivity and minimized non-linear mass dependent fractionation are desirable. In this study, we investigated the effects of three different cone combinations and the addition of N2 with the guard electrode, either grounded or floating, on the performance of Nd isotope analyses. Signal enhancements (2.5–3 folds) were observed for the Jet sample cone + X skimmer cone and for the standard sample cone + X skimmer cone, which were compared to those of the standard sample cone + H skimmer cone with the addition of N2 at 3 or 6 ml min−1. The influence of a guard electrode on the LA-MC-ICP-MS sensitivity was minimal for dry plasma conditions but became significant in the presence of N2. The addition of 3 or 6 ml min−1 N2 into the carrier gas increased the sensitivity for Nd by a factor of 1.6 with the GE-on mode for the Jet sample cone + X skimmer cone. However, in the GE-off mode, the addition of 2–3 ml min−1 N2 decreased the signal intensity of Nd by a factor of two to three. The makeup gas flow rate was found to have a significant effect on the mass bias stability of Nd isotopes, and this effect was different for different cone combinations. To stabilize the mass bias, measurements at elevated makeup gas flow rates was required for the combination of the X skimmer cone with the standard sample cone or Jet sample cone, at the expense of sensitivity. In notable contrast, the mass bias was stable for the combination of the standard sample cone and H skimmer cone under their corresponding optimum makeup gas flow rates. However, we found that the neodymium isotopes exhibited a large non-linear component at elevated makeup gas flow rates that could not be corrected by the accepted mass fractionation laws. The addition of 3–6 ml min−1 nitrogen to the central gas flow in laser ablation MC-ICP-MS was found to not only significantly enlarge the mass bias stability zone, but also to suppress the non-linear mass dependent fractionation for the combination of X skimmer cone with Jet sample cone or standard sample cone. The accuracy and precision of the developed analytical method for Nd isotope using Jet sample cone + X skimmer cone with the addition of nitrogen has been demonstrated by analyzing a series of reference glasses (JNdi-1 glass, LREE glass, NIST 610) and minerals (apatite, monazite and titanite). Results obtained for 143Nd/144Nd ratios in these reference materials are in excellent agreement with published values, demonstrating the capability of the developed analytical method to be an important tool for providing high-quality in situ Nd isotope data in geological samples.
TL;DR: A review of developments in atomic spectrometry can be found in this paper, which covers atomic emission, absorption, fluorescence and mass spectrometers, but excludes material on speciation and coupled techniques which is included in a separate review.
Abstract: This review covers developments in ‘Atomic Spectrometry’. It covers atomic emission, absorption, fluorescence and mass spectrometry, but excludes material on speciation and coupled techniques which is included in a separate review. It should be read in conjunction with the other related reviews in the series.1–6 A critical approach to the selection of material has been adopted, with only novel developments in instrumentation, techniques and methodology being included. Developments worthy of note include photochemical and electrochemical methods of vapour generation, single particle analysis using ICP-MS and the development of new methods for direct plasma generation in liquid samples. The use of MC-ICP-MS continues to grow in importance for isotope ratio measurements in fields as diverse as geochronology, nuclear forensics and biomedical research. Laser-based methods are also important in many fields, particularly for direct and stand-off analysis of solid samples.
TL;DR: In this paper, the applicability of a multi-step generic procedure to systematically develop sample preparation methods for the detection, characterization, and quantification of inorganic engineered nanoparticles (ENPs) in a complex matrix was successfully demonstrated.
Abstract: The applicability of a multi-step generic procedure to systematically develop sample preparation methods for the detection, characterization, and quantification of inorganic engineered nanoparticles (ENPs) in a complex matrix was successfully demonstrated. The research focused on the optimization of the sample preparation, aiming to achieve a complete separation of ENPs from a complex matrix without altering the ENP size distribution and with minimal loss of ENPs. The separated ENPs were detected and further characterized in terms of particle size distribution and quantified in terms of elemental mass content by asymmetric flow-field flow fractionation coupled to a multi-angle light scattering detector and an inductively coupled plasma mass spectrometer. Following the proposed generic procedure SiO2-ENPs were separated from a tomato soup. Two potential sample preparation methods were tested these being acid digestion and colloidal extraction. With the developed method a complete SiO2-ENPs and matrix separation with a Si mass recovery >90% was achieved by acid digestion. The alteration of the particle size distribution was minimized by particle stabilization. The generic procedure which also provides quality criteria for method development is urgently needed for standardized and systematic development of procedures for separation of ENPs from a complex matrix. The chosen analytical technique was shown to be suitable for detecting SiO2-ENPs in a complex food matrix like tomato soup and may therefore be extended to monitor the existence of ENPs during production and safety control of foodstuffs, food labelling, and compliance with legislative limits.
TL;DR: A review of the intergrity of As species during collection, storage, sample preparation and measurement by HPLC-ICPMS and HPLC HG-AFS is presented in this article.
Abstract: The importance of measuring arsenic (As) species has been appreciated for a long time mainly because of the wide spread knowledge of arsenic's toxicity and its use as a poison. Increasingly health, environmental and food regulations have been written around As species rather than total concentrations. Knowledge of As speciation is important as the chemical form of As controls its bioavailability, toxicity, mobility and therapeutic benefits. Arsenic is present as inorganic (arsenate, arsenite, thioarsenates), complexed (arsenic glutathionines and phytochelatins), low molecular weight (monomethylarsonate, dimethylarsenate, arsenobetaine, arsenocholine etc.) and high molecular weight (arsenic hydrocarbons and arsenic phospholipids) species. In this review we cover the intergrity of As species during collection, storage, sample preparation and measurement by HPLC-ICPMS and HPLC-HG-AFS. It is essential to ensure that As species, especially in waters and sediments, are not artefacts of the preservation or extraction procedure. Most samples can be stored frozen (−20 °C), but the stability of water and sediment samples is matrix dependent and depends on preservation technique applied. Arsenic cannot be extracted from samples using a single set of conditions but must be optimised for each sample type. Methanol–water mixtures with microwave heating are commonly used to extract polar As species from tissues while As-lipids required a non-polar solvent. Dilute acid can be used to increase the efficiencies of extraction of hard to extract tissue As species. Freeze drying is suitable for the drying of biotic material while sediments should not be dried before analysis. Extraction efficiencies are critically dependent on particle size. Polar As species have a wide variety of ionic characteristics thus complimentary chromatographic approaches utilising ion-exchange or reverse phase columns with modifiers are needed to separate all the As species. Arsenic-lipids require the use of a reverse phase column and gradient elution with high concentrations of organic solvents and require compensation for carbon enhancement effects in the ICPMS. Care must be taken that chromatographic peaks are not misidentified and matrix interferences accounted for that may influence quantification. Finally, to ensure accurate results, mass balances and extraction and column recoveries need to be determined at all steps. Methods need to be evaluated using As spikes and certified reference materials to provide a means of assessing the quality of results.
TL;DR: The results suggest that the optimal sample preparation method to study elemental distribution in single whole cells prepared for X-ray microanalysis is achieved when cells are rinsed with ammonium acetate, quickly frozen by plunging into liquid nitrogen–chilled cryogenic fluid and freeze-dried at low temperatures.
Abstract: Particle induced X-ray emission with a focused beam (μPIXE) and synchrotron-based X-ray micro-fluorescence (μSXRF) are used to determine the distribution and contents of trace elements in single cells. A proper sample preparation method is required to ensure that the elemental distribution is preserved spatially and quantitatively. The aim of this study was to establish an optimal sample preparation method for single whole cell microanalysis, compatible with both μPIXE and μSXRF techniques. To find the most efficient method, we used PC12 cells as the cellular model and compared four widely applied protocols using a combination of rinsing solutions (phosphate buffered saline or ammonium acetate) and fixation methods (cryofixation or chemical fixation with 3% paraformaldehyde or methanol). The results showed a loss of diffusible elements K and Mg and an increase in Na, S, Cl and Zn concentrations in chemically fixed cells compared to cryofixed cells. In addition, K/Na and Cl/K cellular ratios indicated a good preservation of the chemical and structural integrity of cryofixed cells but not those of chemically fixed ones. The disturbance of elemental distributions after chemical fixation was also observed on rat brain tissue sections. Our results suggest that the optimal sample preparation method to study elemental distribution in single whole cells prepared for X-ray microanalysis is achieved when cells are rinsed with ammonium acetate, quickly frozen by plunging into liquid nitrogen–chilled cryogenic fluid and freeze-dried at low temperatures. This protocol was also successfully validated on rat primary hippocampal neurons, a delicate in vitro neuronal model.
TL;DR: The ASU review as mentioned in this paper focuses on advances in elemental speciation and covers a period of approximately 12 months from December 2014, covering all aspects of the analytical atomic spectrometry speciation methods developed for: the determination of oxidation states; organometallic compounds; coordination compounds; metal and heteroatom-containing biomolecules, including metalloproteins, proteins, peptides and amino acids.
Abstract: This is the eighth Atomic Spectrometry Update (ASU) to focus on advances in elemental speciation and covers a period of approximately 12 months from December 2014. This ASU review deals with all aspects of the analytical atomic spectrometry speciation methods developed for: the determination of oxidation states; organometallic compounds; coordination compounds; metal and heteroatom-containing biomolecules, including metalloproteins, proteins, peptides and amino acids; and the use of metal-tagging to facilitate detection via atomic spectrometry. The review does not cover fractionation, which is sometimes termed operationally defined speciation. As with all ASU reviews the focus of the research reviewed includes those methods that incorporate atomic spectrometry as the measurement technique. However, because speciation analysis is inherently focused on the relationship between the metal(loid) atom and the organic moiety it is bound to, or incorporated within, atomic spectrometry alone cannot be the sole analytical approach of interest. For this reason molecular detection techniques are also included where they have provided a complementary approach to speciation analysis. As in previous years, As and Se speciation continues to dominate the current literature and there has also been an increase in the number of publications concerning solid state speciation. This is presumably due to the increase in the number of synchrotron facilities available and a greater awareness of their potential for speciation studies.
TL;DR: In this article, the authors assess the factors (light, halides) influencing the instability of red mercury sulfide and understand the chemical equilibria governing the formation and evolution of different degradation compounds.
Abstract: The red pigment mercury sulfide, called cinnabar or vermilion, is well known to suffer from an alteration giving rise to a grey, grey-white or black color at the surface of degraded works of art. This phenomenon can dramatically affect the esthetical value of artworks. This work aims at assessing the factors (light, halides) influencing the instability of red mercury sulfide and understanding (by combining thermodynamic and experimental approaches) the chemical equilibria governing the formation and evolution of the different degradation compounds. From the thermodynamic study of the Hg–S–Cl–H2O system, it was concluded that Hg(0), Hg3S2Cl2, and Hg2Cl2 can be formed from the reaction of α-HgS with ClO(g). In the second part, the artificial ageing experiments presented were carried out on model samples following the conditions assessed in the first part, in order to reproduce natural ageing observed on red mercury sulfide. Similarly to degradation compounds detected on original works of art, mercury chlorine compounds such as calomel (Hg2Cl2) and corderoite (α-Hg3S2Cl2) were identified on the surface of α-HgS model samples, when exposed to light and a sodium hypochlorite solution. Sulfates were detected as well, and more particularly gypsum (CaSO4·2H2O) when Ca was originally present in the model sample. The relationship between color and composition is discussed as well.
TL;DR: In this paper, a multi-spectral-line calibration (MSLC) approach based on an artificial neural network (ANN) was developed to improve the accuracy and precision of steel analysis using laser-induced breakdown spectroscopy (LIBS).
Abstract: A multi-spectral-line calibration (MSLC) approach based on an artificial neural network (ANN) was developed to improve the accuracy and precision of steel analysis using laser-induced breakdown spectroscopy (LIBS). The intensity ratios of multiple spectral lines of target and matrix elements were used to train an ANN. The resulting model was able to relate the spectra to the concentrations of target elements more accurately than the conventional internal calibration approach, which led to improvements in the accuracy and precision of the LIBS analysis. This approach was applied to LIBS analysis of steel samples to predict the Cr and Ni concentrations. Compared with a conventional internal calibration approach, the root-mean-square errors of cross-validation for Cr and Ni decreased from 0.018 and 0.067 wt% to 0.010 and 0.023 wt%, respectively, using the proposed MSLC, and the average values of the relative standard deviation for Cr and Ni decreased from 11.3 and 19.5% to 6.4 and 12.9%, respectively.