Showing papers in "Journal of Analytical Atomic Spectrometry in 2009"
TL;DR: In this paper, a two-volume laser-ablation cell coupled with a quadrupole ICPMS is described, which combines rapid ( 10000 cps/ppm for mid-high m/z, 55 μm, 5 Hz).
Abstract: A new custom-built excimer (193 nm) laser-ablation system with two-volume laser-ablation cell coupled to a quadrupole ICPMS is described, which combines rapid ( 10000 cps/ppm for mid-high m/z, 55 μm, 5 Hz). An application of reconstructing medieval Pb exposure highlights the need for rapid signal washout in unravelling strongly varying Pb peaks in well-preserved archaeological tooth enamel.
325 citations
TL;DR: In this article, a robust procedure that allows for the combined chemical separation of Mg, Ca and Fe, using ion-exchange columns that contain 1 ml AG50W-X8 (200-400 mesh) cation exchange resin was reported.
Abstract: Near quantitative separation of analyte elements from the sample matrix is commonly required to obtain precise and accurate stable isotope data, especially if MC-ICP-MS is used in conjunction with the standard-sample bracketing (SSB) technique for mass bias drift correction. Here, we report a robust procedure that allows for the combined chemical separation of Mg, Ca and Fe, using ion-exchange columns that contain 1 ml AG50W-X8 (200–400 mesh) cation exchange resin. Magnesium was separated for isotope ratio analyses from many geological sample types by a single pass through this column. For Mg purification, Be, Ti, Mn, Fe and Al are selectively eluted using dilute HF and an acetone–HCl mixture. The separation of Mg from Ca-dominated carbonate samples and/or a combination of Mg, Ca and Fe separation from the same sample aliquot, is achieved by the adsorption of Ca and Fe onto the ion-exchange resin from 10 M HCl. Following purification, geological reference materials, including water, bone, carbonate and sediment samples, igneous and sedimentary rocks and a chondritic meteorite were analysed by MC-ICP-MS (Mg and Fe isotopes) and double-spike TIMS (Ca isotopes). Average external repeatabilities were ±0.16‰ for 26Mg/24Mg, ±0.26‰ for 44Ca/40Ca and ±0.05‰ for 56Fe/54Fe (2sd; n ≥ 5). Comparison with published data documents the accuracy of the results. For Mg isotope analyses using SSB-MC-ICP-MS, matrix-induced mass bias effects were studied using element additions. The artificial matrices left a memory in subsequent standard analyses, likely due to depositions on the cones. This observation allowed for the detection of matrix effects in unknown samples. Finally, the current status of Mg and Ca zero-delta reference materials is briefly discussed.
164 citations
TL;DR: In this paper, the analytical performance, capabilities, pros and cons, and trends of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), secondary ion (neutral) mass Spectrometer (SIMS/SNMS), and glow discharge (GD-MS) are discussed.
Abstract: Inorganic mass spectrometric techniques and methods for direct solid analysis are widely required to obtain valuable information about the multi-elemental spatial distribution of the major and trace constituents and/or isotope ratio information of a sample in a wide variety of solid specimens, including environmental wastes, biological samples, geochemical materials, coatings and semiconductors. The increasing need to characterize complex materials in industry (e.g. production control and quality assurance processes), and in different fields of science is forcing the development of various inorganic mass spectrometric methods for direct solid chemical analysis. These methods allow the characterization of solid materials both in bulk and in spatially resolved analysis (with lateral and/or in-depth resolution). This review critically discusses the analytical performance, capabilities, pros and cons, and trends of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), secondary ion (neutral) mass spectrometry (SIMS/SNMS), and glow discharge mass spectrometry (GD-MS) because they represent the most widespread and powerful inorganic mass spectrometric methods currently further improved and applied for the direct characterization of solids.
150 citations
TL;DR: In this paper, a tutorial review on the use of single-collector and multicollector ICPMS for isotope ratio determination is presented, with a focus on the mechanisms behind the isotopic variation for those elements for which isotopic analysis can be realized using ICP-mass spectrometry, i.e. the occurrence of radiogenic nuclides formed as a result of the decay of naturally occurring and long-lived radionuclides and mass fractionation as a consequence of thermodynamic and kinetic isotope fractionation effects.
Abstract: This article is intended as a tutorial review on the use of single-collector and multi-collector ICPMS for isotope ratio determination. The monitoring and quantification of both induced and natural differences in the isotopic composition of target elements is covered. The capabilities of various types of ICPMS instruments for isotope ratio measurements are addressed and issues, such as the occurrence of mass discrimination and detector dead time effects and appropriate ways of correcting for the biases they give rise to are discussed. Applications relying on induced changes include elemental assay via isotope dilution, tracer experiments with stable isotopes, aiming at a more profound insight into physical processes or (bio)chemical reactions, and nuclear applications. Attention is also paid to the origin of natural variations in the isotopic composition, with focus onto the mechanisms behind the isotopic variation for those elements for which isotopic analysis can be realized using ICP-mass spectrometry, i.e. the occurrence of radiogenic nuclides formed as a result of the decay of naturally occurring and long-lived radionuclides and mass fractionation as a result of thermodynamic and kinetic isotope fractionation effects. Geochronological dating via the Rb–Sr, U, Th–Pb, and Pb–Pb methods is briefly explained and also the use of Sr and Pb isotopic analysis for provenance determination studies is covered. Subsequently, applications based on isotopic analysis of elements showing a much narrower range of variation as a result of isotope fractionation are described. Next to provenance studies, such applications include the use of isotope ratios in geochemical, environmental and biomedical studies. Although it is not the intention to comprehensively review the literature, several examples of published applications are used to illustrate the capabilities of both single-collector and multi-collector ICPMS in this context. Thereby, attention is devoted both to widely accepted applications and to more ‘exotic’ applications, aiming at an extension of the application range.
141 citations
TL;DR: In this article, a hyphenated methodology has been developed and validated, which utilizes the extensive size separation range of hydrodynamic chromatography (here: 5-300 nm) combined with the multi-element selectivity of ICP-MS.
Abstract: A hyphenated methodology has been developed and validated, which utilizes the extensive size separation range of hydrodynamic chromatography (here: 5–300 nm) combined with the multi-element selectivity of ICP-MS. This has been applied to the analysis of metal-based nanoparticles in environmental samples. The quality of the particle sizing data obtained from this exercise was enabled through the production of a range of gold nanoparticles (sterically stabilized to prevent aggregation in environmental matrices), which were validated for use as external size calibration standards as well as internal retention time markers, using TEM. The methodology was then successfully applied to a study where nanosilver was spiked into sewage sludge, preliminary data from which showed that a fraction of nanosilver survived as single nanoparticles in the sludge supernatant. The method was also tested on solutions containing other commonly used nanoparticles (TiO2, SiO2, Al2O3 and Fe2O3).
Overall, the data showed that, by using ICP-MS with collision cell technology, the methodology would be helpful in investigating the fate of a significant range of nanoparticle types. Other characteristics of HDC-ICP-MS are: rapid analysis time ( 300 nm), and limited sample pre-treatment required.
136 citations
TL;DR: In this paper, a high sensitivity method for measurements of Nd isotopes as NdO+, on a TIMS using a single W filament with TaF5 as an ion emitter is presented.
Abstract: In this paper, a high sensitivity method for measurements of Nd isotopes as NdO+, on a TIMS using a single W filament with TaF5 as an ion emitter is presented. Although analyzing Nd isotopes as oxides (NdO+) is a well known technique, this is the first report to analyze Nd isotopic compositions as oxides using W filaments and the TaF5 emitter. When 0.5–1 ng loads of a Neodymium isotopic reference reagent, JNdi-1, were measured using this method, the ion yields were found to be mostly in excess of 15% and could be as high as 32%. Internal precision on 143Nd/144Nd could be better than 10 ppm (2SE) for 1 ng JNdi-1 loads and better than 15 ppm (2SE) for 0.5 ng JNdi-1 loads; thirteen replicates of 0.5–1 ng JNdi-1 loads yielded a 143Nd/144Nd value of 0.512112 ± 0.000028 (2SD). Compared with the previously reported NdO+ measurement method using the Re (or W) filaments + Silica-gel + H3PO4 loading techniques, this method has advantages including higher sensitivity, a more stable ion beam, and no need for oxygen gas to be bled into the ion source chamber. Sm isotopes were analyzed as Sm+ using the W filaments and the TaF5 emitter, and high sensitivity and good ion beam stability were also obtained. Several international rock reference materials, including an ultramafic rock reference material USGS PCC-1 that contains very low amounts of Sm and Nd, were analyzed with full column chemistry and the TaF5 method, and the results of Sm, Nd concentrations and Nd isotopic data are in good agreement with the reported values. Combined with a highly efficient and low-blank column chemistry to separate Nd from Sm, Ce, and Pr, this method holds potential to analyze Sm, Nd concentrations and Nd isotopic compositions of highly depleted peridotites; very small aliquots of minerals such as garnets; extra-terrestrial materials of limited sample size; and environmental samples that contain very low quantities of Sm and Nd.
132 citations
TL;DR: In this article, a novel approach combining thermal ionization mass spectrometry (TIMS) with the use of an 87Sr/84Sr double spike (DS) was presented for the IAPSO sea water and JCp-1 coral standards.
Abstract: Recent findings of natural strontium isotope fractionation have opened up a new field of research in non-traditional stable isotope geochemistry. While previous studies were based on data obtained by MC-ICP-MS we here present a novel approach combining thermal ionization mass spectrometry (TIMS) with the use of an 87Sr/84Sr double spike (DS). Our results for the IAPSO sea water and JCp-1 coral standards, respectively, are in accord with previously published data. The strontium isotope composition of the IAPSO sea water standard was determined as δ88/86Sr = 0.386(5)‰ (δ values relative to the SRM987), 87Sr/86Sr* = 0.709312(9) n = 10 and a corresponding conventionally normalized 87Sr/86Sr = 0.709168(7) (all uncertainties 2SEM). For the JCp-1 coral standard we obtained δ88/86Sr = 0.197(8)‰, 87Sr/86Sr* = 0.709237(2) and 87Sr/86Sr = 0.709164(5) n = 3. We show that by applying this DS-TIMS method the precision is improved by at least a factor of 2–3 when compared to MC-ICP-MS.
126 citations
TL;DR: In this article, a novel approach to laser ablation Pb/U geochronology is presented that allows accurate determination of isotope ratios from a single pulse of a 193 nm laser.
Abstract: A novel approach to laser ablation Pb/U geochronology is presented that allows accurate determination of isotope ratios from a single pulse of a 193 nm laser. Data are acquired using a low volume ablation cell that facilitates: (1) production of a high density particle stream; and (2) a short (∼0.5 s) sample washout time. Isotope ratios from an individual laser pulse are calculated by integrating the baseline-subtracted total number of counts for the entire pulse and assigning an internal uncertainty based on counting statistics. This ‘total signal integration’ method eliminates the effects of differing detector response times, particularly in multi-collector-inductively coupled plasma-mass spectrometry (MC-ICP-MS), providing an alternative means to quantify transient signals. Data from reference zircons indicate that it is possible to consistently measure 206Pb/238U and 207Pb/206Pb ratios with external reproducibilities of 2% and 2.8% (2SD) respectively, using a similar amount of material to standard static ablation protocols. Decreasing sample consumption to ∼14 ng zircon (∼75% less than the ‘normal’ ablated mass) results in only a modest increase in the uncertainty to ∼5% on the 206Pb/238U ratio. By analysing consecutive laser pulses from the same ablation site, isotopic depth profiles can be generated with a depth resolution of ∼0.1 µm pulse−1. This technique offers a new opportunity to identify complexities within accessory minerals that were previously beyond the spatial resolution of laser based geochronology methods.
116 citations
TL;DR: In this paper, the analytical benefit of an alternative in the form of large geometry SIMS (LG-SIMS), which combines high transmission with high mass resolution, was evaluated by comparing results from actual nuclear inspection samples measured on both instruments.
Abstract: The isotopic analysis of particles containing sub-pg to pg levels of uranium, released from nuclear material handling, has been proven as an efficient tool for international safeguard purposes Precise and accurate measurement of both enrichment and the minor isotopes is, however, a challenging analytical task due to the low levels of material One of the mainstay techniques for particle measurement is Secondary Ion Mass Spectrometry (SIMS), this study evaluates the analytical benefit of an alternative in the form of large geometry SIMS (LG-SIMS), which combines high transmission with high mass resolution We report here that LG-SIMS instruments provide a significantly better measurement quality than the small geometry SIMS as almost all isobaric background interferences are removed at a high useful ion yield Useful yield measurements, performed on uranium oxide particles with calibrated uranium content, showed an overall useful yield of 12% for the LG-SIMS at a mass resolution of 3000 These improvements were then demonstrated by comparing results from actual nuclear inspection samples measured on both instruments Additional benefits include an increased ability to detect particles of interest in a dust matrix while simultaneously reducing the time of sample analysis An evaluation on the performance of LG-SIMS compared to Thermal Ion Mass Spectrometry (TIMS) is also presented This evaluation shows that LG-SIMS has an advantage due to its high ion yield but with a limitation in the detection limit of 236U at higher enrichments due to the necessity for a hydrogen correction
113 citations
TL;DR: In this article, the authors measured elemental sensitivity ratios (ESRs) from a multi-element solution and from the laser ablation of a range of silicate reference materials (SRM 61X series, MPI-DING glasses, USGS basalt glasses).
Abstract: To determine the degree to which matrix affects elemental abundance measurements in LA-ICP-MS analysis, and describe these effects in term of elemental properties, we measured elemental sensitivity ratios (ESRs) from a multi-element solution and from the laser ablation of a range of silicate reference materials (SRM 61X series, MPI-DING glasses, USGS basalt glasses). For all analyses, ESRs depend strongly on element mass and first ionization potential (FIP), as expected. For laser ablation of the nearly transparent SRM 612, ESRs show an additional dependence on elemental temperature of condensation (Tc), such that ESRs of refractory elements are lower than predicted by their mass and FIP dependences. To explore the relationship between this volatility dependence and matrix transparency, we exploited the range of transparency available in the SRM 61X series. With increasing transparency of glasses, LA-ICP-MS analyses showed progressive volatility dependence, with measured concentrations of refractory elements being lower, and measured concentrations of volatile elements being higher, than reported concentrations. For the most transparent glass (SRM 614), concentration offsets from the reported concentrations of the refractory and volatile elements were ∼20%; for SRM 612 offsets were ∼10–15%. We show that this effect is minimized, and possibly negated, by increasing laser energy output. As the offsets for ESRs of refractory elements are uniformly lower in more transparent SRM 612 relative to SRM 610 (11% ± 4%; 1.1 mJ laser energy), successful matrix-independent standardization of refractory elements is possible if the internal normalizing element is approximately the same Tc as the elements to be reported (e.g., Ca and REEs). Volatile elements, however, do not produce uniform ESRs in transparent samples and matrix-independent standardization of volatiles in transparent samples with a 213 nm wavelength laser ablation system will include element-specific systematic errors of the order of tens of percent. All non-transparent glasses analyzed (MPI-DING glasses and USGS BHVO-2G and BCR-2G) show no resolvable matrix-dependent elemental fractionation and may be used interchangeably with an accuracy of better than 10%. In non-transparent samples, the greatest limitation to accurate LA-ICP-MS standardization is the uncertainty in reported reference material concentrations. Matrix-independent standardization of LA-ICP-MS analysis of non-transparent silicates and ceramics, then, is an accurate and viable tool that can best be employed by avoiding calibration with transparent standards, unless using an internal normalizing element of similar Tc to that of the elements to be reported. LA-ICP-MS analysis of transparent silicates and ceramics can be performed at the highest laser energy possible to minimize volatility effects, and calibrated with an internal normalizing element of similar Tc to that of the elements to be reported, using both transparent and non-transparent standards.
108 citations
TL;DR: In this article, a commercially available strontium-specific extraction chromatographic resin based on a crown ether (Sr spec™) was evaluated for use in applications of Sr isotope ratio analysis dealing with samples displaying a complex and/or Ca-rich matrix composition.
Abstract: This paper presents a systematic evaluation of a commercially available strontium-specific extraction chromatographic resin based on a crown ether (Sr spec™), for use in applications of Sr isotope ratio analysis dealing with samples displaying a complex and/or Ca-rich matrix composition. A protocol, consisting of (i) loading a sample digest in 7 M HNO3 onto the resin, (ii) rinsing the resin with 7 M HNO3 to remove concomitant matrix elements and (iii) rinsing the resin with 0.05 M HNO3 to strip off the purified Sr fraction, was found to provide the best results. The performance in terms of (i) the purity of the Sr fraction obtained, (ii) the efficiency of Rb/Sr and Ca/Sr separation, (iii) the Sr recovery from samples with a complex and Ca-rich matrix composition and (iv) the Sr isotope ratios obtained using multi-collector ICP-MS, was evaluated for various amounts (250, 500, 750 and 2000 µL) of resin using digests of bone and soil certified reference materials, dental tissues, fluorite and glass samples. Further, it was investigated whether or not the isolation protocol introduces Sr isotopic fractionation. Also the possibility of regenerating the resin after use, allowing multiple use of the resin, was assessed. Finally, the Sr isotopic composition of 2 bone (NIST SRM 1400 Bone Ash and NIST SRM 1486 Bone Meal) and 2 soil (BCR CRM 141 Calcareous Loam Soil and BCR CRM 142 Light Sandy Soil) certified reference materials was determined. The method was shown to be fit-for-purpose for population migration studies and provenancing of archaeological artefacts, and is expected to be suited for a broad range of Sr isotope ratio applications.
TL;DR: Variations of sample preparation of the human colon carcinoma cell line SW480 exposed in vitro to the tumor-inhibiting metal complexes cisplatin and indazolium trans-[tetrachlorobis(1H-indazole)ruthenate(iii)] (KP1019) prior to analysis with ICP-MS) were found to be tremendously influenced by adsorption to the culture dishes.
Abstract: Cellular uptake is being widely investigated in the context of diverse biological activities of metal compounds on the cellular level. However, the applied techniques differ considerably, and a validated methodology is not at hand. Therefore, we have varied numerous aspects of sample preparation of the human colon carcinoma cell line SW480 exposed in vitro to the tumor-inhibiting metal complexes cisplatin and indazolium trans-[tetrachlorobis(1H-indazole)ruthenate(III)] (KP1019) prior to analysis with ICP-MS, and the results were found to be tremendously influenced by adsorption to the culture dishes. Adsorption to culture plates increases linearly with the concentration of KP1019, depends on the protein content of the medium, the duration of contact to protein-containing medium prior to drug addition and the hydrophilicity/lipophilicity of the compound. For varying degrees of cell confluence, adsorption of Ru hardly differs from cell-free experiments. Desorption from the plates contributes to total Ru detected in dependence on the cell harvesting method. Desorption kinetics for lysis in HNO3 and tetramethylammonium hydroxide (TMAH) are comparable, but TMAH is a more potent desorbant. Sample storage conditions prior to analysis influence significantly the recovery of analyte. Protocols using cell lysis in the culture plate without proper corrections run the risk of producing artefacts resulting from metal adsorption/desorption to an extent comparable with the actual cellular content. However, experimental protocols reported in the literature frequently do not contain information whether adsorption or blank correction were performed and should be regarded with caution, especially if lysis was performed directly in the culture dishes.
TL;DR: In this article, a combination of laser-induced breakdown spectroscopy (LIBS) and laser induced fluorescence (LIF) was investigated to improve the limit of detection (LoD) of trace elements in liquid water, while preserving the distinctive on-line monitoring capabilities of LIBS analysis.
Abstract: The combination of laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) was investigated to improve the limit of detection (LoD) of trace elements in liquid water, while preserving the distinctive on-line monitoring capabilities of LIBS analysis. The influence of the main experimental parameters, namely the ablation fluence, the excitation fluence, and the inter-pulse delay was studied to maximize the fluorescence signal. The plasma was produced by a 266 nm frequency-quadrupled Q-switched Nd:YAG laser and the trace elements under investigation were then re-excited by a nanosecond optical parametric oscillator (OPO) laser, delivering pulses in the sub-mJ energy range, and tuned to strong absorption lines of the trace elements. The reproducibility of the measurements was improved using a home-made flow-cell, and relative standard deviations as low as 6.7% for a series of 100 shots were attained with a repetition rate of 0.7 Hz. Using the LIBS-LIF technique, we demonstrated LoDs of 39 ppb and 65 ppb for Pb and Fe, respectively, accumulating over 100 laser shots only, which correspond to an improvement of about 500 times with respect to LIBS.
TL;DR: In this article, the authors discuss the influence of the aforementioned parameters and processes on LA-ICP-MS and present proposals to map out strategies for optimum LA-ICP-MS analyses, and identify experiments which still need to be done for better understanding of the relevant processes and further improvement of the analytical performance of the technique.
Abstract: Experimental parameters and processes important in laser ablation such as the wavelength, fluence and pulse width of the laser, the form of the ablation cell, the cell gas, the particle transport and atomization in the ICP have an impact on the analytical performance of laser ablation inductively coupled mass spectrometry. The paper discusses the influence of the aforementioned parameters and processes on LA-ICP-MS and presents proposals to map out strategies for optimum LA-ICP-MS analyses. Additionally, experiments are identified which still need to be done for better understanding of the relevant processes and further improvement of the analytical performance of the technique.
TL;DR: In this paper, the state-of-the-art analytical methods available for element speciation in petroleum-related matrices are discussed with particular attention given to chromatography with plasma source atomic spectrometric detection.
Abstract: Challenges to identification, characterisation and determination of element species in crude and residual oils, oil fractions, natural gas and gas condensates, and related products are presented. The principal elements of concern include vanadium, nickel, sulfur, mercury and arsenic. The state-of-the-art of analytical methods available for element speciation in petroleum-related matrices is discussed with particular attention given to chromatography with plasma source atomic spectrometric detection. Methods for fractionation of metal species prior to chromatography are critically reviewed. Analysis for metal species by gas (GC) and liquid chromatography (LC) using different separation mechanisms (size-exclusion, adsorption, ion-exchange, reversed and normal-phase) and element selective detection are discussed. The potential and limitations of LC-ICP AES, LC-ICP MS, GC-MIP AES and GC-ICP MS are highlighted in the context of techniques allowing a direct insight into the metal coordination in petroleum-related samples, such as X-ray absorption spectroscopy (XAS), electron paramagnetic resonance (EPR) and molecular mass spectrometry (using laser desorption, electrospray and chemical ionization).
TL;DR: A small chamber in brass has been developed in order to enhance the sensitivity of single-pulse laser-induced breakdown spectroscopy (LIBS) for element determination in air as mentioned in this paper.
Abstract: A small chamber in brass has been developed in order to enhance the sensitivity of single-pulse Laser-Induced Breakdown Spectroscopy (LIBS) for element determination in air. Its use results in an increase of a factor of 3 and 10 for As and Fe signals detected in the UV range (230–240 nm).
TL;DR: In this paper, a simplified energy-resonant ion-atom reaction was proposed to explain the non-linear mass fractionation observed by high sensitivity skimmers in ICP-MS.
Abstract: A number of prototype high sensitivity skimmers have been developed at Nu Instruments. Signal enhancements of up to a factor of 5 were observed, depending on the element and the sampler–skimmer spacing. However, when using these high sensitivity skimmers, the instrumental mass fractionation for neodymium displayed a large non-linear component that could not be corrected for using the accepted mass fractionation laws. It is proposed that the origin of this non-linear mass fractionation is the formation of NdO+ close to the skimmer surface. The degree of oxide formation, and hence fractionation, is isotope dependent but it is not a linear function of mass. A decrease in the measured xNd/144Nd ratio, relative to standard values, is associated with a concomitant increase in the same ratio in NdO+ (and vice versa). The observed inverse relationship between the metal and oxide species is consistent with mass balance calculations. The magnitude of this effect was dependent on conditions at the skimmer surface (geometry, surface coating, etc.) and could be suppressed by the addition of small amounts of N2 to the carrier gas flow. A simplified energy-resonant ion-atom reaction is postulated to explain these observations, and can be extended to a general model of REE oxide formation in the supersonic expansion. The non-linear fractionation observed also appears to correlate with deviations (from a linear function of mass) in the nuclear charge radii. This is the first evidence of nuclear volume effects contributing to the instrumental mass fractionation in ICP-MS.
TL;DR: In this paper, a laser-ablation laser-induced breakdown spectroscopy (LA-LIBS) was proposed as a novel analytical scheme with goals of improved analyte response, minimization of sample matrix effects, and use of non-matrix matched standards.
Abstract: Laser-ablation laser-induced breakdown spectroscopy (LA-LIBS) is proposed as a novel analytical scheme with goals of improved analyte response, minimization of sample matrix effects, and use of non-matrix matched standards. A direct comparison of the LA-LIBS approach and a traditional direct LIBS analysis was made for a set of seven reference materials, ranging from nearly pure iron to copper-nickel and aluminum alloys. The precision of each approach was assessed using calibration curves, and the LA-LIBS configuration was demonstrated to consistently produce a superior analytical response, as assessed by the linear least-squares fit correlation coefficient and y-intercept values. Significantly, the normalized (by Fe) response of the four targeted analyte species (Al, Mn, Mg and Cu) was successfully reduced to a single calibration curve with the LA-LIBS approach. In addition, particle size measurements of the laser-ablation plume were recorded along with SEM and white-light interferometry analysis of ablation craters for assessment of the analytical sample as presented to the analytical LIBS plasma. Finally, the effect of carrier gas is explored by substitution of nitrogen with helium.
TL;DR: The HPLC-ICP-MS method was successfully applied for the determination of MeHg speciation in a dogfish muscle sample after enzymatic hydrolysis with trypsin, and provided the first analytical evidence for the presence and dominance of MehgCys in fish muscle.
Abstract: Monomethylmercury (MeHg+ and its complexes; hereafter referred to as MeHg) in the intracellular environment is known to be predominantly bonded to thiol-containing biomolecules, but the actual identities of these target biomolecules remain unknown. While binding with glutathione acts as a detoxification mechanism for MeHg, binding with L-cysteine is thought to be the main pathway of MeHg transport across the blood–brain barrier. Here we report a HPLC-ICP-MS method that is capable of separating and analyzing MeHg-cysteine complexes (MeHgCys; charges are neglected for simplicity) and MeHg-glutathione complexes (MeHgGlu), as well as MeHgX (X = H2O, OH−, or Cl−) and inorganic HgX, with detection limits at the sub-micromolar levels. The method was successfully applied for the determination of MeHg speciation in a dogfish muscle sample after enzymatic hydrolysis with trypsin, and provided the first analytical evidence for the presence and dominance of MeHgCys in fish muscle.
TL;DR: In this article, the detection and discrimination of explosive residues on a variety of surfaces using laser-induced breakdown spectroscopy and partial least squares discriminant analysis is discussed, and the correlation between the hardness of a substrate and the ability to discriminate residues on that substrate is discussed.
Abstract: We have demonstrated the detection and discrimination of explosive residues on a variety of surfaces using laser-induced breakdown spectroscopy and partial least squares discriminant analysis. The correlation between the hardness of a substrate and the ability to discriminate residues on that substrate is discussed. We have also shown that while using the full spectra in the chemometric model improves the classification of sample types in the model, the use of intensities and ratios specific to explosive residues improves the classification of sample types that are not part of the model. In the first case, differences in the laser-induced plasma (and resulting spectral features) attributable to the laser-material interaction contribute to the sample discrimination, while using intensities and ratios specific to explosive residues focuses on the chemical composition of the sample for discrimination. Combining the results of the two models for a given sample set decreases the overall false positive rate for all test samples.
TL;DR: In this article, a double spike (DS) method for determining the mass-dependent fractionation (MDF) of cadmium isotopes is described, where samples are spiked with a mixed 106Cd-108Cd tracer prior to high-purity anion exchange based separation of Cd.
Abstract: Natural mass-dependent fractionation (MDF) of cadmium isotopes is a promising new tool for investigating Cd pathways and cycling in geological and biological materials. One interesting new application is as chemical tracer of deep water circulation and nutrient distribution in the oceans. But since natural isotope fractionation of Cd appears to be extremely limited and Cd abundances low, excellent external precision and sensitivity are needed to make full use of its potential. Here, we describe a newly-developed double spike (DS) method for determining the MDF of Cd isotopes. For inorganic matrices, samples are spiked with a mixed 106Cd-108Cd tracer prior to high-purity anion exchange-based separation of Cd. Isotope measurements are performed by TIMS using a silica gel activator. Overall, the DS-TIMS technique offers benefits in terms of superior precision and sensitivity compared to MC-ICPMS methods currently in use. External precisions on 100-ng-sized Cd standard loads, double spiked as unknowns, are ±14 ppm on the 112Cd/110Cd ratio (2SD), while ionization efficiencies (ions per atom loaded) are ∼0.3%. Using this technique, we calibrated the relative difference in MDF between several Cd standard materials used in various laboratories as “zero reference standards”. We also show that the 112Cd/110Cd ratio can be fractionated by as much as ∼0.2% by ion-exchange elution, which is potentially problematic for Cd isotope studies not using a double spike.
TL;DR: In this paper, the results were obtained with a Q-switched Nd:YAG laser (1064 nm), characterized by 5.3 ns duration pulses at a maximum repetition frequency of 10 Hz and with pulse energy up to 300 mJ.
Abstract: The calibration-free methodology described in the literature dealing with the technique of laser induced breakdown spectroscopy has been applied here to several samples under different operating pressures with the aim of classifying the analytical technique as quantitative, semi-quantitative or qualitative (with quantitative estimates only), depending on the relative percentage errors calculated for the major, minor and trace elemental composition of the sample. The results were obtained with a Q-switched Nd:YAG laser (1064 nm), characterized by 5.3 ns duration pulses at a maximum repetition frequency of 10 Hz and with pulse energy up to 300 mJ. The spectra were taken with a grating monochromator coupled with an intensified CCD detector, calibrated from 220 to 700 nm. The samples investigated were aluminum alloy standard disks, standard reference materials of Zn alloy, Cu–Ni alloy, Ti alloy, Ni alloy powder, Cu–Zn alloy and soils. The data are compared with those published in the literature. The results show that the best accuracy (5% relative error) is usually obtained for the matrix element, while in most cases, for the remainder of the components in the sample (major, minor or trace composition), the results can only be considered semi-quantitative (<200% relative error).
TL;DR: A review of analytical 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 as mentioned in this paper.
Abstract: This is the fourth Atomic Spectrometry Update (ASU) to focus specifically on developments in elemental speciation and covers a period of approximately 12 months from January 2011. The International Union for Pure and Applied Chemistry (IUPAC) has evaluated speciation and provided a definition as follows: “speciation analysis is the analytical activity of identifying and/or measuring the quantities of one or more individual chemical species in a sample; the chemical species are specific forms of an element defined as to isotopic composition, electronic or oxidation state, and/or complex or molecular structure; the speciation of an element is the distribution of an element amongst defined chemical species in a system.” This review therefore deals with all aspects of the analytical 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 operationally defined ‘speciation’, which is correctly termed fractionation. As with all ASU reviews1–6 the coverage of the topic is confined to those methods that incorporate atomic spectrometry as the measurement technique. However, in the spirit of meeting the needs of the subject, material is incorporated that is not strictly “atomic spectrometry” but the separation or sample introduction technique used could also be coupled with an atomic spectrometry detector. For the most part, such procedures are those in which some form of molecular MS is used for speciation measurements. As the content of this Update shows, the field is now maturing as evidenced by the extent to which the speciation of particular elements or technique combinations have been the subject of review articles. However, it is becoming increasingly difficult to ascertain the analytical details of the methodologies applied in speciation analysis, particularly where the paper is published in an ‘application’ based journal.
TL;DR: In this paper, the authors review currently proposed Se metabolic pathways in animals and plants and point out ambiguous selenometabolites from the viewpoint of speciation, and highlight some metabolites required for solid verification of the metabolic chart.
Abstract: Selenium (Se) shows ambivalent characteristics in animals and plants. It is an essential element in animals but becomes severely toxic when the amount ingested exceeds the required level. Meanwhile, Se is not essential in plants although some plants are Se hyperaccumulators. As Se changes into several chemical forms when metabolized, the identification of selenometabolites is considered to correspond to the depiction of the metabolic chart of Se. Hence, we are very much interested in unveiling selenometabolomes, i.e., the entirety of selenometabolites. Speciation with elemental and molecular mass spectrometry coupled with separation techniques has significantly contributed to the discovery of selenometabolomes. At the same time, speciation has highlighted some metabolites required for solid verification of the metabolic chart. The aim of this article is to review currently proposed Se metabolic pathways in animals and plants and to point out ambiguous selenometabolites from the viewpoint of speciation.
TL;DR: In this paper, it was shown that explosives detection is possible behind a barrier placed between a target and a standoff LIBS sensor, such as polymethylmethacrylate (PMMA) and a variety of glasses.
Abstract: Development studies reveal that explosives detection is possible behind a barrier placed between a target and a standoff LIBS sensor. Barriers such as polymethylmethacrylate (PMMA) and a variety of glasses have been tested. Results for the detection of organic (DNT, TNT, C4 and H15) and inorganic (sodium chlorate) explosive residues placed up to 30 m from the sensor are presented. The standoff experiments have been evaluated in the emission (studies on laser beam transmission sent by the sensor) and collection (studies on plasma light emission collected by the sensor) channels. These experiments open wide perspectives for the detection of IEDs (improvised explosive devices) through windows located, for instance, inside vehicles, industrial warehouses and buildings where explosive residues have been produced, handled, stored or prepared.
TL;DR: In this paper, a new and sensitive method is described for the on-line determination and preconcentration of ultra-trace nickel using the coupling of a flow injection system with graphite furnace atomic absorption spectrometry.
Abstract: A new and sensitive method is described for the on-line determination and preconcentration of ultra-trace nickel using the coupling of a flow injection system with graphite furnace atomic absorption spectrometry. The method is based on photochemical generation of Ni(CO)4 and its trapping on the surface of a graphite furnace, the latter accomplished with approximately 35% efficiency by exposing a solution of Ni(II), containing formic acid, to UV irradiation. Optimum conditions for generation and trapping, as well as interferences from concomitant elemental ions, were investigated. A characteristic mass of 10 pg and LOD of 8 pg mL−1 were obtained based on a 2 ml sample volume. The LOD can be further enhanced by increasing sample volume and reaction temperature, or by addition of copper ions. The precision was better than 3% (RSD) at 1 ng mL−1. Environmental Certified Reference Materials were analyzed to validate the accuracy of the proposed method, including SLRS-4 (river water), MESS-3 (marine sediment), TORT-2 (lobster hepatopancreas) and DOLT-3 (fish liver tissue).
TL;DR: In this article, the authors evaluated the speciation and distribution of Se in Se-enriched rice and non-supplemented rice by ion-paring reversed phase (IP-RP) and strong anion-exchange (SAX) chromatography coupled with inductively coupled plasma mass spectrometry (ICPMS) detection.
Abstract: Se-enriched rice was prepared by foliar fertilization. In the present work, speciation and distribution of Se in Se-enriched rice and non-supplemented rice was evaluated by ion-paring reversed phase (IP-RP) and strong anion-exchange (SAX) chromatography coupled with inductively coupled plasma mass spectrometry (ICPMS) detection. Three extraction procedures: water extraction, acid extraction (0.1 M HCl) and enzymatic hydrolysis were studied with a combination of protease XIV and amylase with ultrasonic bath and the latter was found to be optimal for the extraction of selenospecies. The chromatograms obtained revealed that the major selenospecies found in Se-enriched rice was selenomethionine (SeMet), which was further identified by nanoelectrospray ionization, ion trap mass spectrometry (nano-ESI-ITMS). Approximately 86.9% of the total Se in the Se-enriched rice extract was SeMet, while only 26.7% of non-supplemented rice extract was due to SeMet. Moreover, nearly 60% of inorganic Se in the form of SeIV was present in the non-supplemented rice, while only 6.8% of inorganic Se as SeIV and SeVI was found in Se-enriched rice extract with minor selenocystine (SeCys2) and trace selenomethionine selenoxide (SeOMet) present. The results proved that SeMet was efficiently extracted by the enzymatic hydrolysis without oxidization. The high SeMet concentrations of Se-enriched rice indicate a high inorganic to organic conversion when Se enrichment was carried out by foliar application. Since SeMet is a readily bioavailable Se species for animals, Se-enriched rice could be considered for supplementation in Se poor geographical regions.
TL;DR: In this paper, a system for trace analysis of multiple heavy metals was developed wherein a magnetic nano-adsorbent was integrated with a lab-on-valve system and coupled this to an inductively coupled plasma mass spectrometer.
Abstract: A novel system for trace analysis of multiple heavy metals was developed wherein we have integrated a magnetic nano-adsorbent with a lab-on-valve system and coupled this to an inductively coupled plasma mass spectrometer. The magnetic nano-adsorbent was prepared by surface modification of iron-based magnetic nanoparticles with polyacrylic acid (MNPs-PAA). The MNPs-PAA possessing the superparamagnetic nature of MNPs could be controllably immobilized in PTFE tubing by an external magnetic force. The high surface density of PAA (3.30 × 1011 molecules cm−2) on MNPs-PAA significantly reduced the amounts of adsorbent needed for adsorption of heavy metals (Mn2+, Co2+, Cu2+, Zn2+, and Pb2+). A detection limit of 0.04–0.06 µg L−1 (except 0.6 µg L−1 for Cu2+ and Zn2+), a precision smaller than 4% (RSD, n = 3), and a linear range of 0.5–50 µg L−1 were obtained by directly injecting an aliquot of 20 µL fortified standard solution analyzed at 5 min per sample. The accuracy was evaluated by analyzing certified reference materials of SRM 2670a (trace elements in urine, low level) and CASS-2 (nearshore seawater reference material for trace metals). Good agreement between the measured and certified values demonstrated that the system is useful for trace analysis of multiple heavy metals in environmental and biological aqueous samples. The potential of integrating functionalized nano-materials to improve the performance of existing analytical systems as an alternative approach to green analytical chemistry is foreseen.
TL;DR: In this paper, two standard free approaches to the quantitative analysis of aluminum alloys by laser-induced breakdown spectroscopy (LIBS) are compared: the calibration-free LIBS (CF-LIBS), and the Monte Carlo simulated annealing optimization method (MC -LIBS).
Abstract: Two standard free approaches to the quantitative analysis of aluminum alloys by laser-induced breakdown spectroscopy (LIBS) are compared—the calibration-free LIBS (CF-LIBS) approach and the Monte Carlo simulated annealing optimization method (MC-LIBS). The experiments are carried out under a pressure of 0.1 mbar, using a Nd-YAG at 1064 nm, with a 5.3 ns nominal pulse width, an energy of 90 mJ/pulse and a spot size on the target of 0.070 cm, resulting in an irradiance of 4.4 GW/cm2. The spectra are taken with a grating monochromator calibrated over a wide spectral range and equipped with an intensified CCD detector. A gate width of 100 ns has been chosen for the measurements. In the MC model, a direct-inverse approach is used, where simulated and experimental spectra are correlated with each other until a satisfactory correlation coefficient is obtained. Spatially resolved measurements are also performed, by recording the plasma emission in the imaging mode and binning the resulting image into 11 different spatial positions along the axial direction, each binned region being equivalent to ∼ 0.025 cm portion of the vertical plasma partition. The spectrum obtained for each spatial position is still spatially integrated along the line-of-sight. Comparatively, concentration values obtained with CF-LIBS for the matrix element Al are much closer to the certified values than those obtained with MC-LIBS (4% versus 20% relative errors, respectively), while the relative concentration obtained for the remainder of the sample components resulted in relative errors that are comparable in magnitude with both approaches (30%–250% relative errors). It is argued that the necessity of improving the space and time resolution of the experimental set-up appears to be at least as important as that of refining the theoretical models.
TL;DR: In this paper, a simple method with a fast sample preparation procedure for total and inorganic mercury determinations in blood samples is proposed based on flow injection cold vapor inductively coupled plasma mass spectrometry (FI-CV ICP-MS).
Abstract: A simple method with a fast sample preparation procedure for total and inorganic mercury determinations in blood samples is proposed based on flow injection cold vapor inductively coupled plasma mass spectrometry (FI-CV ICP-MS). Aliquots of whole blood (500 µL) are diluted 1 + 1 v/v with 10.0% v/v tetramethylammonium hydroxide (TMAH) solution, incubated for 3 h at room temperature and then further diluted 1 + 4 v/v with 2.0% v/v HCl. The inorganic Hg was released by on-line addition of L-cysteine and then reduced to elemental Hg by SnCl2. On the other hand, total mercury was determined by on-line addition of KMnO4 and then reduced to elemental Hg by NaBH4. Samples were calibrated against matrix-matching. The method detection limit was found to be 0.80 µg L−1 and 0.08 µg L−1 for inorganic and total mercury, respectively. Sample throughput is 20 samples h−1. The method accuracy is traceable to Standard Reference Material (SRM) 966 Toxic Metals in Bovine Blood from the National Institute of Standards and Technology (NIST). For additional validation purposes, human whole blood samples were analyzed by the proposed method and by an established CV AAS method, with no statistical difference between the two techniques at 95% confidence level on applying the t-test.