Showing papers in "Journal of Analytical Atomic Spectrometry in 2012"
TL;DR: In this article, the effect of three different cone combinations on the performance of laser ablation MC-ICP-MS (Neptune plus) for the in situ Hf isotope analysis of zircon were investigated.
Abstract: The effect of three different cone combinations on the performance of laser ablation MC-ICP-MS (Neptune plus) for the in situ Hf isotope analysis of zircon were investigated. The signal sensitivities of Hf, Yb and Lu were improved by a factor of 1.4 and 2.5, respectively, with using the X skimmer cone + standard sampler cone and the X skimmer cone + Jet sample cone compared to the standard arrangement (H skimmer cone + standard sample cone). However, when using the high-sensitivity Jet sample cone, the instrumental mass fractionation for hafnium displayed a large non-linear component that could not be corrected using the normal mass fractionation laws. The magnitude of this non-linear mass fractionation was strongly related to the central gas flow rate. The in situ Hf isotope analysis of zircon standards 91500 and Mud Tank using the Jet cone displayed large deviations (410–470 ppm) at the optimum central gas flow rate for Hf, which seriously deteriorated the performance of the Jet cone. The addition of 4 ml min−1 nitrogen to the central gas flow in laser ablation MC-ICP-MS was found to not only increase the sensitivity of Hf by a factor of 2.1, but also suppress this non-linear mass fractionation. The determined Yb/Hf and Lu/Hf ratios at their corresponding optimum makeup gas flow rates for Hf intensity were found to be reduced by factors of 2 and 1.3 in the presence of nitrogen, respectively, which would benefit the accurate in situ determination of Hf isotopes in high-content Yb and Lu samples. Compared to the standard arrangement, the corresponding precision (2σ) of 176Hf/177Hf for single spot analysis of zircon standard 91500 was improved from 224 ppm to 50 ppm by using the newly designed X-skimmer cone and Jet sample cone in combination with the nitrogen addition technique. The determined 176Hf/177Hf ratios are in excellent agreement with published values in five reference zircon standards (91500, GJ-1, Mud Tank, Penglai and Plesovice). Our first Hf isotopic results from zircon standard M257 (0.281544 ± 0.000018; 2SD, n = 151) showed that it was fairly homogeneous in Hf isotopes. These results clearly demonstrate that the present analytical method has the potential to become an important tool for the pursuit of high-quality in situ Hf isotope data for zircons.
760 citations
TL;DR: In this article, the authors compared the ability of two emerging techniques to detect well characterized, monodisperse silver ENPs and examined their overall applicability to environmental studies specifically with respect to their size and concentration detection limits, resolution and multi-form elemental analysis.
Abstract: Methods to detect, quantify, and characterize engineered nanoparticles (ENPs) in environmental matrices are highlighted as one of the areas of highest priority research needs with respect to understanding the potential environmental risks associated with nanomaterials. More specifically, techniques are needed to determine the size and concentration of ENPs in a variety of complex matrices. Furthermore, data should be collected at environmentally and toxicologically relevant concentrations. Both single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) and asymmetrical flow field flow fractionation (AF4) ICP-MS offer substantial advantages for detecting ENPs and assessing many of the above parameters in complex matrices over traditional characterization methods such as microscopy, light scattering, and filtration. In this study, we compared the ability of two emerging techniques to detect well characterized, monodisperse silver ENPs and examined their overall applicability to environmental studies specifically with respect to their: (A) size and concentration detection limits, (B) resolution and (C) multi-form elemental analysis. We find that in terms of concentration detection limit (both, on a mass basis and particle number basis) SP-ICP-MS was considerably more sensitive than AF4-ICP-MS (ng L−1vs. μg L−1, respectively), and offers the unique ability to differentiate dissolved and nanoparticulate fractions of total metal. With a variety of optimization parameters possible, AF4-ICP-MS can detect a much smaller NP size (2 nm vs. 20 nm for SP-ICP-MS), provides the possibility for greater size resolution.
256 citations
TL;DR: In this article, the unique considerations to determine the number of particles per liter and analyte mass distributions from single particle ICP-MS measurements with quadrupole or sequential sector field mass spectrometers are discussed.
Abstract: The unique considerations to determine the number of particles per liter and analyte mass (particle size) distributions from single particle ICP-MS measurements with quadrupole or sequential sector field mass spectrometers are discussed. The short, transient nature of signals from single particles affects the optimum selection of dwell times and pulse counting versus analog detection. The signal peak width due to a cloud of ions produced from a single particle also limits the maximum number of single particles that can be accurately measured in a given total measurement time and the dynamic range of the particle number concentration. The range of analyte mass (particle size) measurements is limited by the rates of vaporization and diffusion. Approaches to calibrate the number of particles detected as a function of the number of particles per mL and to calibrate the signal from a single particle as a function of analyte mass are discussed. Measurement of particle diameter distributions for spherical, solid particles are assessed.
177 citations
TL;DR: For example, the authors found that small beer, wort drinks, stews, and pottage may have been regularly consumed by children during the Medieval period, and this culturally mediated behaviour could have affected the oxygen isotope composition of their water intake beyond that which is accommodated in the current conversion equations used in archaeological studies to assess environmental origins.
Abstract: ‘Small beer’, ‘wort drinks’ and ‘pottage’ may have been regularly consumed by children during the Medieval Period. This culturally mediated behaviour could have affected the oxygen isotope composition of their water intake beyond that which is accommodated in the current conversion equations used in archaeological studies to assess environmental origins. Experimental data shows that brewing may increase the δ18O value of ale by 1.3‰ over that of the initial water (‘liquor’) used, boiling water to make hot drinks raises the δ18O value of the fluid consumed by ∼0.4‰ and slow-cooking using a large stew pot results in an increase in the oxygen isotope composition of the ‘pottage’ by an average of 10.2‰ after 3 hours of cooking. Thus, if ingested fluids included 20% from ale, 10% from ‘teas’ and 20% from stews (the latter increased from −7.0‰ to +3.2‰ by three hours of cooking) then the overall effect on the calculated drinking water value from the tooth enamel will be +2.3‰.
137 citations
TL;DR: A compilation of strontium and oxygen isotope data from human tooth enamel that has been produced at NERC Isotope Geosciences Laboratory over the last c.15 years is presented in this article.
Abstract: This paper presents a compilation of strontium and oxygen isotope data from human tooth enamel that has been produced at NERC Isotope Geosciences Laboratory over the last c.15 years. These many and often small studies are here combined to provide an overview of data from Britain. The strontium isotope composition ranges between 0.7078 and 0.7165 (excluding individuals deemed to be of non-British origin). The median Sr concentration is 84 ppm but there is a vector of increasing Sr concentrations related to seawater strontium isotope composition that is seen in individuals predominantly from the west coast of Scotland attributed to the used of kelp as a fertilizer. The oxygen isotope data is normally distributed with a mean value of 17.7‰ ± 1.4‰ (2SD n = 615). Two sub-populations of local individuals have been identified that provide control groups for human enamel values from the eastern side of Britain where there are lower rainfall levels: 17.2‰ ± 1.3‰, (2SD, n = 83) and western area of Britain where rainfall levels are higher = 18.2‰ ± 1‰, (2SD, n = 40). These data make it possible to make direct comparisons of population means between burial populations and the control dataset to assess commonality of origin.
132 citations
TL;DR: In this article, the authors describe the first systematic comparison and optimisation of extraction methods for titanium dioxide nanoparticles in sunscreen samples, based on sample spiking with aluminium-labeled titanium dioxide reference particles of known size.
Abstract: Titanium dioxide in nanoparticulate form is used in large scale in a variety of consumer products including sunscreens. There is an increasing need for methodology for the reliable characterisation of the particle size and size dependent elemental composition in these complex matrices. Such measurement capability is essential for underpinning safety assessments, for quality control of existing products and for correlation of nanoparticle characteristics with biological effects observed in toxicity tests. This work describes the first systematic comparison and optimisation of extraction methods for titanium dioxide nanoparticles in sunscreen samples. Sunscreens were selected because of their wide use, high fat content and matrix of high complexity. Defatting of the sample with hexane followed by bath sonication with an aqueous extractant was found to provide stable suspensions of secondary titanium dioxide particles for their size characterisation by flow field flow fractionation on-line with element selective detection by inductively coupled plasma mass spectrometry. Further addition of a small amount of hexane to the aqueous extractant resulted in particle disaggregation and thus allowed for characterisation of the primary particle size. A novel approach based on sample spiking with aluminium-labelled titanium dioxide reference particles of known size was used to study the effect of extraction and separation conditions on particle size distribution in the presence of the real sample matrix. The developed methodology was applied to analysis of commercial sunscreens with various sun protection factors. Titanium extraction efficiency, particle size distribution and titanium dioxide recovery from the FFF channel were determined for each product.
110 citations
TL;DR: In this article, the authors compared hydrodynamic chromatography (HDC) and asymmetrical flow field flow fractionation (AF4), both coupled with inductively coupled plasma mass spectrometry (ICP-MS), in their capacity to detect, quantify, and characterize nanoparticles.
Abstract: Robust methods to detect and characterize engineered nanoparticles (ENPs) in environmental samples are an urgent need, particularly given the increasing use of ENPs in consumer products. To be successful, methods should enable differentiation of ENPs from background nanoparticulates and other system components. The element specificity of inductively coupled plasma mass spectrometry (ICP-MS) can, to some degree, satisfy this requirement. Given the polydisperse nature of particles in natural systems, combining ICP-MS with a size separation method holds particular promise. This paper compares hydrodynamic chromatography (HDC) and asymmetrical flow field flow fractionation (AF4), both coupled with ICP-MS, in their capacity to detect, quantify, and characterize nanoparticles. The detection limits, resolution, and recoveries for both techniques were determined using gold nanoparticle standards. AF4 is capable of separating mixtures of 5, 20, 50 and 100 nm gold ENPs with significantly greater resolution than HDC, with these resolution differences being most pronounced in the smaller size range. However, HDC recoveries ranged from 77 to 96%, while recovery during AF4 ranged from 4 to 89%. The low AF4 recoveries generally occurred for the largest ENPs at the lowest concentrations examined. The limits of detection for both techniques were found to be approximately 5 μg L−1, however different experimental conditions could lower this value. HDC provides an additional benefit over AF4 by proving capable of separating a dissolved signal from a NP sample.
105 citations
TL;DR: In this article, a matrix-dependent partitioning of carbon into carbon containing gaseous species (CCGS) and carbon containing particles (CCP) was observed while trace element analytes are exclusively transported as the particulate phase.
Abstract: Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is considered a mature technique for the quantitative analysis of various soft and solid materials but is still lacking suitable calibration standards, in particular, for biological and medical applications. Therefore, most quantification strategies rely on in-house prepared standards. Due to its availability and apparent homogeneity in biological and medical matrices carbon is frequently used as an internal standard. Although the applicability of carbon as internal standard has already been in dispute over years its behaviour during LA is not well-understood. This work deals with the analysis of twelve common carbon matrices using a gas exchange device (GED) to investigate the formation of carbon-containing gaseous species (CCGS) during LA. A matrix-dependent partitioning of carbon into CCGS and carbon containing particles (CCP) was observed while trace element analytes are exclusively transported as the particulate phase. The production of CCGS was also found to critically depend on the presence or absence of oxygen (matrix or gas impurities) and the affinity of matrix constituents towards oxygen.
100 citations
TL;DR: In this article, the detection and sizing of metal-containing engineered nanoparticles (ENPs) was achieved at concentrations predicted for environmental samples (part-per-trillion levels) using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS).
Abstract: Detection and sizing of metal-containing engineered nanoparticles (ENPs) was achieved at concentrations predicted for environmental samples (part-per trillion levels) using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). Silver nanowires, titanium dioxide and cerium oxide nanoparticles were found to be detectable by this technique, while zinc oxide dissolved too quickly for analysis at these concentrations. In addition to the potential dissolution of particles, other considerations affecting ENP analysis include: instrumental background, mass interferences, percent metal in a nanoparticle, and isotopic abundance of the analyte element. Sizing of these metal-containing nanoparticles was done by correlating ICP-MS response (pulses) from ENPs entering the plasma to mass of metal in dissolved standards. The resulting particle size distributions compared well with results from sedimentation field-flow fractionation. Coincidence in ENP pulses may be difficult to detect in the broad size distributions that arise from polydisperse samples. Comparison of data obtained by combination of multiple analyses of dilute solutions to single analyses of higher concentration allowed discrimination between coincidence and polydispersity. The ratio of ENP pulse detections to the total number of readings during analysis was optimized at 2.5% or less to minimize coincident pulses while still allowing definition of a size distribution.
99 citations
TL;DR: In this paper, a multi-collector ICP-mass spectrometry (MC-ICP-MS) was used for the isotopic analysis of Cu, Fe and Zn, isolated from human whole blood.
Abstract: Multi-collector ICP-mass spectrometry (MC-ICP-MS) was used for the isotopic analysis of Cu, Fe and Zn, isolated from human whole blood. For chromatographic isolation of these elements, the method first described by Marechal, Telouk and Albarede (Chem. Geol., 1999, 156, 251–273) and relying on the use of AG MP-1 strong anion exchange resin was further tailored and subsequently validated. It was shown that all three target elements could be obtained in pure form and with quantitative recovery from Seronorm whole blood reference material. MC-ICP-MS isotope ratio measurement conditions were optimized so as to avoid the influence of spectral overlap and the capabilities of several methods to correct for instrumental mass discrimination were compared. The method developed was then applied to a set of whole blood samples from supposedly healthy volunteers (reference population). For Fe, the by now well-known difference in isotopic composition between blood from male and female individuals was confirmed. The isotopic composition of Zn in whole blood was assessed to be governed by the diet as a significant difference could be established between blood from vegetarians and from omnivores, respectively. For the isotopic composition of Cu, interpretation of the results is more challenging, as neither gender, nor diet seems to have a significant influence, but the combined influence of both factors may show an effect.
97 citations
TL;DR: In this paper, a simple analytical approach using batch dynamic light scattering (DLS) is proposed for a fast assessment of samples containing unknown ENP types or structures, which can be used to detect unwanted particle-membrane interactions, which often lead to inappropriate recovery rates in A4F fractionation.
Abstract: The analysis of engineered nanomaterials (ENMs), especially engineered nanoparticles (ENPs), is a fast growing analytical research field. New trends in plasma spectrometry such as direct single particle inductively coupled plasma mass spectrometry (spICPMS) or the coupling of asymmetric flow field flow fractionation to ICPMS (A4F-ICPMS) allow direct analysis of ENPs by getting not only chemical but also size information simultaneously. However, sample handling of nanoparticles could be challenging and change the ENP properties. For most of the analysing techniques, dilution of ENP samples is needed as minimum sample preparation. The colloidal stability and the agglomeration behaviour depend on the ENP-type, the coating or functionalization agent and on the surrounding media. The stability of charge stabilized ENPs is especially sensitive to changes of pH or ionic strength, and sometimes even to dilution. Although the stability of sterically stabilized ENPs is typically less affected by the above-mentioned factors, agglomeration can still occur in certain environments. Thus, storage, handling and sample preparation are big challenges in ENP analysis. Kinetic studies of different ENPs, representative of typical nanoparticle types and coatings, point out that the behaviour is dependent on various influencing factors pertaining to the chemical environment (pH, ionic strength, dilution). In this study polyvinyl alcohol (Ag@PVA) and citrate (Ag@citrate) stabilized silver nanoparticles, as well as titanium oxide ENPs functionalized with poly-acrylate (TiO2@PA) have been studied. A simple analytical approach using batch dynamic light scattering (DLS) is proposed for a fast assessment of samples containing unknown ENP types or structures. Besides aspects of sample handling, unwanted particle–membrane interactions, which often lead to inappropriate recovery rates in A4F fractionation, are investigated here. These interactions are caused by the electrostatic charges carried by different membrane materials and the resulting interaction with the ENPs' charge. This is critically discussed for membrane materials typical for A4F analysis: polyethersulfone (PES), regenerated cellulose (RC), and polyvinylidene difluoride (PVDF).
TL;DR: In this paper, a coal sample was analyzed using a 266 nm Nd:YAG laser in different gas environments (air, argon and helium) at atmospheric pressure and the influence of the ambient gas on the laser-induced coal plasma was studied by using time-resolved analysis.
Abstract: Laser ablation chemical analysis of a coal sample was studied by LIBS (laser-induced breakdown spectroscopy). Ablation was performed using a 266 nm Nd:YAG laser in different gas environments (air, argon and helium) at atmospheric pressure. We present characteristics of spectra measured from coal with special attention to atomic and molecular carbon including CI, C2 and CN. The influence of the ambient gas on the laser-induced coal plasma was studied by using time-resolved analysis. Atomic iron emission lines were employed to construct Boltzmann plots for the plasma excitation temperature. Computer simulations of C2 spectra were used to deduce the molecular rotational temperature. Electron density and total atomic and molecular number density are reported to describe emission differences of atomic and molecular carbon in the different gas environments. These data demonstrate that the plasma excitation temperature is the primary factor contributing to differences among the atomic carbon emission in the gas environments. Reactions between the plasma species and ambient gas, and the total molecular number are main factors influencing molecular carbon emission. Finally, the influence of laser energy on the rotational temperature was studied in the air environment to demonstrate that the rotational temperature derived from C2 band emission can be utilized to correct plasma fluctuations.
TL;DR: In this article, the authors present an approach to create compositional images using a module created for use with the freely distributed software package Iolite, which creates images by synchronizing the state of the laser (e.g., whether the laser is firing or not) and the position on the sample, which are recorded in laser log files, with concurrently collected mass spectrometer data.
Abstract: We present a novel approach to creating compositional images using a module created for use with the freely distributed software package Iolite. The module creates images by synchronising the state of the laser (e.g., whether the laser is firing or not) and the position on the sample, which are recorded in laser log files, with concurrently collected mass spectrometer data. When these two data sources are synchronised, mass spectrometer data which are recorded temporally can then be displayed versus ablation position (i.e., spatially). Each mass spectrometer reading is then plotted as a circular spot representing the size of the area ablated. This approach has many advantages. CellSpace takes advantage of Iolite's ability to manipulate data from various mass spectrometers and to reduce data of different types. Laser ablation data can be plotted over other images, such as those produced by scanning electron microscopes, where the image has been transformed into cell coordinates using third party software. This allows the analyst to visualise laser ablation data in context and to correlate sample data from multiple sources and/or techniques. The code also has the advantage of averaging data spatially, rather than just temporally, and faithfully presents the data as a corresponding laser spot, rather than a simple rectangular pixel. Here we provide an example of a fish otolith, where trace element concentrations and Sr-isotopic compositions are overlain on microscope images, providing information on migration patterns that are applicable to population studies and fisheries conservation.
TL;DR: In this article, a model based on the photochemical generation of free radicals involving ligand to metal charge transfer reductions and oxidations was proposed to account for the production of volatile metal species arising from photochemical vapor generation in acetic and formic acid media.
Abstract: Possible mechanisms are advanced to account for a number of observations/phenomena associated with the production of volatile metal species arising from photochemical vapor generation in acetic and formic acid media. These systems include mercury, iodine, selenium, iron and nickel as test cases which generate cold vapor, hydrides, methylated and carbonylated species. A model, based on the photochemical generation of free radicals involving ligand to metal charge transfer reductions and oxidations, is consistent with the majority of experimental data, including the identity of the resultant species and the impact of external parameters. This mechanistic framework will hopefully serve to enhance understanding of the technique so as to elicit enhanced performance through development of improved hardware and minimization/control of interferences.
TL;DR: In this paper, the authors compared different data-driven multivariate statistical predictive algorithms for the quantitative analysis of Fe content in iron ore measured using Laser-Induced Breakdown Spectroscopy (LIBS).
Abstract: The objective of the current research was to compare different data-driven multivariate statistical predictive algorithms for the quantitative analysis of Fe content in iron ore measured using Laser-Induced Breakdown Spectroscopy (LIBS). The algorithms investigated were Principal Components Regression (PCR), Partial Least Squares Regression (PLS), Multi-Block Partial Least Squares (MB-PLS), and Serial Partial Least Squares Regression (S-PLS). Particular emphasis was placed on the issues of the selection and combination of atomic spectral data available from two separate spectrometers covering 208–222 nm and 300–855 nm ranges, which include many of the spectral features of interest. Standard PLS and PCR models produced similar prediction accuracy, although in the case of PLS there were notably less latent variables in use by the model. It was further shown that MB-PLS and S-PLS algorithms which both treated available UV and VIS data blocks separately, demonstrated inferior performance in comparison with both PCR and PLS.
TL;DR: In this article, the analytical performance of three sample introduction systems, a PFA micronebulizer with a Peltier-cooled cyclonic spray chamber (PC3), an APEX Q, and a monodisperse droplet generator (Microdrop) with an in-house built spray chamber, was compared for the characterization of silver nanoparticles (Ag NP) with different sizes (20-100 nm) using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS).
Abstract: Engineered nanomaterials are used increasingly around the world. In recent years, environmental concerns have being raised that call for risk assessment, toxicity studies, and nanosafety policies. It is therefore important to provide analytical tools that are able to characterize various types of nanomaterials in a sensitive and fast fashion. In this study, the analytical performance of three sample introduction systems, a PFA micronebulizer with a Peltier-cooled cyclonic spray chamber (PC3), a PFA micronebulizer with a heated cyclonic spray chamber and three-stage Peltier-cooled desolvation system (APEX Q), and a monodisperse droplet generator (Microdrop) with an in-house built spray chamber, was compared for the characterization of silver nanoparticles (Ag NP) with different sizes (20–100 nm) using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). With continuous polydisperse and pulsed monodisperse droplet sample introduction, single 30 nm NP (PC3) and 20 nm NP (APEX Q, Microdrop), respectively, were successfully detected. Detection efficiencies (20–100 nm Ag NP) were in the range of 5.8 × 10−5 to 8.2 × 10−5 counts per atom, cpa (PC3), 7 × 10−5 to 9.5 × 10−5 cpa (APEX Q), and 8.1 × 10−5 to 1.2 × 10−4 cpa (Microdrop). For a given nanoparticle sample, the variation of the relative standard deviation (RSD) of the size distribution width among the three systems was found to be 1–4% (e.g. 1.3% for 100 nm Ag NP with RSDs of 16.3%, 16.8%, and 17.6% for Microdrop, APEX Q, and PC3, respectively). Size measurements performed by SP-ICP-MS were validated by transmission electron microscopy measurements. Because silver toxicity depends on the silver species in the sample, simultaneous detection of Ag NP and free Ag(I) ions was studied with droplet sample introduction.
TL;DR: In this article, carbon and nitrogen stable isotope ratios were measured in 157 fish bone collagen samples from 15 different archaeological sites in Belgium which ranged in ages from the 3rd to the 18th c. AD.
Abstract: Carbon and nitrogen stable isotope ratios were measured in 157 fish bone collagen samples from 15 different archaeological sites in Belgium which ranged in ages from the 3rd to the 18th c. AD. Due to diagenetic contamination of the burial environment, only 63 specimens produced results with suitable C : N ratios (2.9–3.6). The selected bones encompass a wide spectrum of freshwater, brackish, and marine taxa (N = 18), and this is reflected in the δ13C results (−28.2‰ to −12.9%). The freshwater fish have δ13C values that range from −28.2‰ to −20.2‰, while the marine fish cluster between −15.4‰ and −13.0‰. Eel, a catadromous species (mostly living in freshwater but migrating into the sea to spawn), plots between −24.1‰ and −17.7‰, and the anadromous fish (living in marine environments but migrating into freshwater to spawn) show a mix of freshwater and marine isotopic signatures. The δ15N results also have a large range (7.2‰ to 16.7‰) indicating that these fish were feeding at many different trophic levels in these diverse aquatic environments. The aim of this research is the isotopic characterization of archaeological fish species (ecology, trophic level, migration patterns) and to determine intra-species variation within and between fish populations differing in time and location. Due to the previous lack of archaeological fish isotope data from Northern Europe and Belgium in particular, these results serve as an important ecological backdrop for the future isotopic reconstruction of the diet of human populations dating from the historical period (1st and 2nd millennium AD), where there is zooarchaeological and historical evidence for an increased consumption of marine fish.
TL;DR: In this paper, double-pulse laser-induced breakdown spectroscopy (DP-LIBS) was performed for quantitative analysis of three metallic trace elements: Fe, Pb and Au in aqueous solutions.
Abstract: Double-pulse laser-induced breakdown spectroscopy (DP-LIBS) was performed for quantitative analysis of three metallic trace elements: Fe, Pb and Au in aqueous solutions. The plasma was generated using a UV (266 nm) frequency-quadrupled Q-switched Nd:YAG laser (7 ns) and then reheated by a 1064 nm Q-switched Nd:YAG laser (7 ns) in a quasi-collinear geometrical configuration. In order to improve the reproducibility of LIBS measurements, a circulation cell was used, providing a reproducibility of about 4% with a laser repetition rate of 0.3 Hz. The influence of the inter-pulse delay and the fluence of the second laser pulse on the signal-to-noise ratio (SNR) for the analytical lines was investigated and optimized. Analytical figures of merit of DP-LIBS and conventional single-pulse LIBS (SP-LIBS) were evaluated by establishing the calibration curves for the Fe I 358.12 nm, Pb I 405.78 nm and Au I 267.60 nm lines. The signal was greatly enhanced in DP-LIBS while the noise level did not vary as much. An improvement of the relative limit of detection of about 10 was achieved using DP-LIBS when compared to UV SP-LIBS in all cases. Measurement of the electron density as a function of time indicates that the plasma plume lifetime is longer in DP-LIBS. Similar trends in the excitation temperature were not observed for reasons that we attribute to larger uncertainties related to the Boltzmann plot method.
TL;DR: The main pathways for greening atomic spectrometry such as downsizing of instrumentation, use of portable instruments, solid sampling, application of clean energies (ultrasound, microwaves, etc.) for sample pre-treatment, development of on-site, on-line and at-line approaches vs. typical off-line methods, and application of modern extraction techniques (e.g., solid-and liquid-phase microextraction), green solvents and derivatization agents and use of chemometric tools for method optimization, signal processing, etc. as discussed by the authors
Abstract: As a result of the greater consciousness within the analytical community on the impact of chemicals on human health and environment, green issues are increasingly taken into account when choosing an established analytical method or developing a new one. Apart from typical analytical characteristics (e.g., sensitivity, limit of detection, repeatability, etc.), other features such as the amount of sample/reagents, operation time, use of energy-effective apparatus, waste production, etc. should be highlighted in order to meet the principles of Green Chemistry. Although conventional approaches for trace element analysis by atomic spectrometry usually involve well-established sample pre-treatments based on ‘wet chemistry’, and high consumption of gases, reagents, etc. is inherent to many techniques in this group, there are still many avenues where green issues can be implemented. For greening atomic spectrometry, green chemistry principles should be applied to every step of the analytical process, i.e., from sampling and sample pre-treatment to data processing. In this review, main pathways for greening atomic spectrometry such as downsizing of instrumentation, use of portable instruments, solid sampling, application of clean energies (ultrasound, microwaves, etc.) for sample pre-treatment, development of on-site, on-line and at-line approaches vs. typical off-line methods, application of modern extraction techniques (e.g., solid- and liquid-phase microextraction), green solvents and derivatization agents and use of chemometric tools for method optimization, signal processing, etc. are discussed in a critical way.
TL;DR: In this article, three cleaning techniques that remove external contamination of human hair are assessed to investigate the potential use of Sr and Pb isotope composition of hair for human provenancing, and they are successfully applied to demonstrate the capability of modern and archaeological human scalp hair and modern human facial hair to record isotope variations related to geographic location.
Abstract: Three cleaning techniques that remove external contamination of human hair are assessed to investigate the potential use of Sr and Pb isotope composition of hair for human provenancing. These techniques are; (i) a centrifugation technique using diiodomethane where hair and soil particles are separated by density difference; (ii) a leaching technique of the hair surface using 2 M HNO3 acid and (iii) cleaning the hair with chloroform, methanol and ultra pure water. These techniques are validated and are successfully applied to demonstrate the capability of modern and archaeological human scalp hair and modern human facial hair to record Sr and Pb isotope variations related to geographic location. In this study, Sr isotope ratios analysed in modern human scalp hair from a female vegetarian and non-smoker register marked isotopic change on a monthly timescale when an individual moves to locations with contrasting Sr isotope compositions. Pb isotope ratios do not show significant changes after moving locations, possibly due to comparable Pb isotope ratios in the two environments. In contrast, Pb isotopes ratios analysed in facial hair from a male omnivore and smoker record isotopic changes within a two week period when moving between locations with significant differences in environmental Pb isotope compositions. Further research is needed to determine the exact rate of change in isotopic composition in scalp and facial hair in humans with different diets and life styles that move from geographical locations with isotopic contrasting composition.
TL;DR: In this article, an on-line solid-phase extraction method linked to inductively coupled mass spectrometry (ICP-MS) was developed for the determination of low levels of uranium and thorium in environmental samples.
Abstract: An on-line solid-phase extraction method linked to inductively coupled mass spectrometry (ICP-MS) has been developed for the determination of low levels of uranium and thorium in environmental samples. The hyphenation of lab-on-valve (LOV) and multisyringe flow injection analysis (MSFIA), coupled to an ICP-MS, allows the simultaneous determination of thorium and uranium in different types of environmental sample matrices achieving high selectivity and sensitivity levels. On-line separation and preconcentration of thorium and uranium are carried out by means of UTEVA resin. The potential of the LOV-MSFIA makes possible the full automation of the system by the on-line regeneration of the column. The limits of detection reached are 0.4 ng L−1 of uranium and 2.8 ng L−1 of thorium. The reproducibility of the LOV-MSFIA-ICP-MS is 1.7% of RSD. Moreover, a high sensitivity, a wide working range (0–200 μg L−1 for uranium and thorium) and an injection frequency up to 9 h−1 (depending on the sample volume) should be highlighted. Different water sample matrices (seawater, well water, freshwater, tap water and mineral water), a phosphogypsum sample with natural uranium and thorium content and a channel sediment reference material were satisfactorily analyzed with the proposed method.
TL;DR: In this article, a novel approach for the chemical purification of Ca from silicate rocks by ion-exchange chromatography, and a highly-precise method for the isotopic analysis of Ca, including the smallest isotope 46Ca (0.003%) was reported.
Abstract: We report a novel approach for the chemical purification of Ca from silicate rocks by ion-exchange chromatography, and a highly-precise method for the isotopic analysis of Ca—including the smallest isotope 46Ca (0.003%)—by high-resolution multiple collector inductively coupled plasma source mass spectrometry (HR-MC-ICPMS), in combination with thermal ionization mass spectrometry (TIMS). Using this approach, we measured the Ca isotope composition of a number of terrestrial rock standards and seawater. Based on these data, we show that the non-mass-dependent abundances of μ43Ca, μ46Ca, and μ48Ca (normalized to 42Ca/44Ca) can be measured with an external reproducibility of 1.8, 45 and 12.5 ppm, respectively, when measured by HR-MC-ICPMS and μ40Ca and μ43Ca to 80 and 23 ppm, respectively, when measured by TIMS (μ notation is the per 106 deviation from the reference material). Comparison with earlier studies demonstrate that it is possible to measure the mass-dependent Ca isotope composition of terrestrial materials using HR-MC-ICPMS with an external reproducibility comparable to that typically obtained with double spike TIMS techniques. The resolution of the mass-independent 43Ca, 46Ca and 48Ca data obtained by HR-MC-ICPMS represents more than a 45-, 120-, and 18-fold improvement, respectively, relative to earlier measurements obtained by TIMS. This improvement allows for a better understanding of the mass fractionation laws responsible for the mass-dependent fractionation of Ca present in natural samples and synthetic standards. For example, the presence of an apparent excess of ∼60 ppm in the μ48Ca composition of the SRM 915a suggests that equilibrium fractionation processes have generated the mass-dependent fractionation of this material. In contrast, the absence of residual anomalies in the mass-independent composition of seawater implies that biogenic and inorganic processes of carbonate formation fractionate Ca kinetically from seawater. Finally, we note that SRM 915b has a mass-dependent and mass-independent Ca isotope composition that is within the resolution of our method identical to that of bulk silicate Earth (BSE). This observation, together with the potential heterogeneity in the 40Ca composition of the SRM 915a inferred from our measurements, suggests that the SRM 915b is a better reference material to study the Ca isotope composition of terrestrial and non-terrestrial materials.
TL;DR: X-ray absorption spectroscopy (XAS) is an element specific spectrography sensitive to the local chemical and structural order of the absorber element as discussed by the authors, which is used for speciation analysis of chemical elements.
Abstract: X-ray absorption spectroscopy (XAS) is an element specific spectroscopy sensitive to the local chemical and structural order of the absorber element. XAS is nowadays increasingly used for the speciation analysis of chemical elements owing to the development of new synchrotron radiation facilities worldwide. XAS can be divided into X-ray absorption near edge structure (XANES), which provides information primarily about the geometry and oxidation state, and extended X-ray absorption fine structure (EXAFS), which provides information about metal site ligation. The main advantages of the XAS method are its subatomic (angstrom) resolution, the ability to analyze almost any type of samples including amorphous (non-crystalline) materials, the possibility to analyze such materials in situ requiring minor or no sample preparation. The main limitations of XAS are its sensitivity in the mM (or μg g−1) range, the difficulty to deconvolute the bulk data when the sample is composed of a mixture of structures of the absorber element, and the limited chemical selectivity of ligands to within one row of the periodic table. This tutorial will discuss the strengths and limitations of XAS and compare them to those of alternative or complementary methods such as X-ray diffraction and X-ray photoelectron spectroscopy. The tutorial will also present and discuss the specific needs in terms of sample preparation and preservation all along the process of storage and analysis, and discuss the importance of the use of cryogenic methods when XAS is applied to biological samples. Applications in life sciences are reviewed, not exhaustively, with a special emphasis on some characteristic examples. The article ends with some perspectives on future trends of XAS: micro- and nano-XAS, time-resolved XAS, and high energy resolution XAS.
TL;DR: In this article, relative elemental sensitivities are reported for a number of sample and skimmer cone combinations, with standard and enhanced pumping of the interface region, for the Thermo Scientific Neptune MC-ICP-MS.
Abstract: Relative elemental sensitivities are reported for a number of sample and skimmer cone combinations, with standard and enhanced pumping of the interface region, for the Thermo Scientific Neptune MC-ICP-MS. An approximate two-fold sensitivity enhancement was observed for Sr, Nd, Hf, Pb and U using the Jet sample cone and an enhanced pumping configuration, compared to the standard arrangement. In the case of Li, the standard sample cone and enhanced pumping configuration gave the maximum sensitivity. In addition to improved ion transmission, the X skimmer cone geometry is also associated with additional contributions to the instrumental mass fractionation (at least in the case of Nd) that do not have a simple exponential dependence on the isotope mass. Neodymium isotope ratios measured using the X cone displayed large deviations (up to ∼750 ppm) from the reference (i.e. ‘true’) values. Similar deviations have been reported previously when using high sensitivity skimmer cone geometries on the Nu MC-ICP-MS instruments (K. Newman et al., J. Anal. At. Spectrom., 2009, 24, 742). The reported non-linear contribution to the instrumental mass fractionation with respect to Nd is not specific to a particular MC-ICP-MS instrument; it is associated with an increase in the NdO+/Nd+ ratio, due to either a change in the plasma operating conditions (e.g. an increase in the sample gas flow, absence of a secondary discharge at the interface, change in plasma gas composition) or modification of the cone geometry. The role of secondary discharge formation and the physical and chemical processes occurring in the supersonic expansion with respect to NdO+ formation are discussed.
TL;DR: In this article, a collision reaction cell-Inductively Coupled Plasma-Mass Spectrometry (CRC-ICP-MS) was applied to ice core samples from Talos Dome, Antarctica.
Abstract: Iron is an element of great interest due to its role in primary production and in oceanic carbon cycle regulation, such that past changes in iron deposition may have influenced oceanic sequestration of atmospheric CO2 on millennial time scales. The behavior of iron in biological and environmental contexts depends strongly on its oxidation state. Solubility in water and the capacity to form complexes are just two important characteristics that are species dependent. Distinguishing between the two iron species, Fe(II) and Fe(III), is necessary to evaluate bioavailability, as Fe(II) is more soluble and therefore more readily available for phytoplankton uptake and growth. Here, we present a novel analytical method for iron speciation analysis using Collision Reaction Cell-Inductively Coupled Plasma-Mass Spectrometry (CRC-ICP-MS) and apply it to ice core samples from Talos Dome, Antarctica. The method detection limit is 0.01 ng g−1. A chelating resin, Ni-NTA Superflow, was used to separate the Fe species. At pH 2 the resin is capable of retaining Fe3+ with no retention of Fe2+. After the initial separation, we oxidized the Fe2+ using H2O2, and determined the Fe2+ concentration as the difference between the two measurements. Our preliminary results demonstrate higher Fe2+ concentrations during glacial periods than during interglacial periods. This elevated concentration of Fe2+ suggests that more iron was available for phytoplankton growth during the Last Glacial Maximum, than would be expected from measurements of proxies such as dust mass or total Fe.
TL;DR: In this paper, the authors evaluate the statistical distribution of the sweep intensities based on goodness-of-fit tests in order to find a model probability distribution fitting the data to apply an appropriate formulation for the standard deviation.
Abstract: U–Pb dating of zircons by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) is a widely used analytical technique in Earth Sciences. For U–Pb ages below 1 billion years (1 Ga), Pb206/U238 dates are usually used, showing the least bias by external parameters such as the presence of initial lead and its isotopic composition in the analysed mineral. Precision and accuracy of the Pb/U ratio are thus of highest importance in LA-ICPMS geochronology. We consider the evaluation of the statistical distribution of the sweep intensities based on goodness-of-fit tests in order to find a model probability distribution fitting the data to apply an appropriate formulation for the standard deviation. We then discuss three main methods to calculate the Pb/U intensity ratio and its uncertainty in the LA-ICPMS: (1) ratio-of-the-mean intensities method, (2) mean-of-the-intensity-ratios method and (3) intercept method. These methods apply different functions to the same raw intensity vs. time data to calculate the mean Pb/U intensity ratio. Thus, the calculated intensity ratio and its uncertainty depend on the method applied. We demonstrate that the accuracy and, conditionally, the precision of the ratio-of-the-mean intensities method are invariant to the intensity fluctuations and averaging related to the dwell time selection and off-line data transformation (averaging of several sweeps); we present a statistical approach how to calculate the uncertainty of this method for transient signals. We also show that the accuracy of methods (2) and (3) is influenced by the intensity fluctuations and averaging, and the extent of this influence can amount to tens of percentage points; we show that the uncertainty of these methods also depends on how the signal is averaged. Each of the above methods imposes requirements to the instrumentation. The ratio-of-the-mean intensities method is sufficiently accurate provided the laser induced fractionation between the beginning and the end of the signal is kept low and linear. We show, based on a comprehensive series of analyses with different ablation pit sizes, energy densities and repetition rates for a 193 nm ns-ablation system that such a fractionation behaviour requires using a low ablation speed (low energy density and low repetition rate). Overall, we conclude that the ratio-of-the-mean intensities method combined with low sampling rates is the most mathematically accurate among the existing data treatment methods for U–Pb zircon dating by sensitive sector field ICPMS.
TL;DR: In this article, sample preparation protocols based on common cation exchange and Sr-specific extraction chromatographic resin were evaluated and investigated for natural geological samples prior to 87Sr/86Sr ratio measurement using MC-ICP-MS or TIMS.
Abstract: In this paper, sample preparation protocols based on common cation-exchange and Sr-specific extraction chromatographic resin were evaluated and investigated for natural geological samples prior to 87Sr/86Sr ratio measurement using MC-ICP-MS or TIMS. Several CRMs and real geological samples were digested using HF, HNO3 and HClO4 in closed vessels prior to sequential chemical purifications and then Sr isotopic ratios were determined by MC-ICP-MS or TIMS. Because HREEs reside in the Sr fraction when common cation-exhange resin is used, this purification technique is unsuitable prior to MC-ICP-MS analysis, as doubly loaded HREE interfere on Sr masses. We observe an obviously positive relationship between the radiogenic 87Sr/86Sr ratio and the content of HREEs in the Sr fractions, as well as a negative relationship between un-radiogenic 84Sr/86Sr or 84Sr/88Sr ratios and the content of HREEs in the Sr fractions during MC-ICP-MS Sr isotopic measurement. Such effects are insignificant for TIMS measurement, because ionization temperatures are generally lower and can be well controlled during the analyses. In contrast to the traditional Sr purification method (cation exchange resin), Sr-specific extraction chromatographic resin produces high purity Sr fractions, making it feasible for both MC-ICP-MS and TIMS.
TL;DR: In this paper, a simple method to calculate the laser scan speeds capable of reducing the acquisition time by up to a factor of 5 whilst maintaining dimensional integrity of the image is presented. But this method does not consider the relationship between laser scan speed, laser spot diameter and the total scan cycle of the quadrupole mass analyser.
Abstract: Elemental bio-imaging experiments by quadrupole-based LA-ICP-MS normally employ scan speeds where the distance traversed in one second is equal to or less than the diameter of the laser beam. Consequently, data for a higher-resolution (pixel size = 15 μm2) image of a 5 mm2 tissue section can take upwards of 30 h to acquire. Appropriate laser scan speeds may be calculated by consideration of the relationship between laser scan speed, laser spot diameter and the total scan cycle of the quadrupole mass analyser. This paper presents a simple method to calculate the laser scan speeds capable of reducing the acquisition time by up to a factor of 5 whilst maintaining dimensional integrity of the image.
TL;DR: In this article, a review of the state of the art in nanoscale SIMS analysis is presented, with a short introduction into recent instrumentation for high resolution SIMS imaging and the limiting factors of lateral resolution.
Abstract: Secondary Ion Mass Spectrometry (SIMS) enables surface chemical analysis of nano-scaled objects and chemical imaging of nano-scaled details of natural or artificial objects. This review presents the state of the art in nanoscale SIMS analysis. At first a short introduction into recent instrumentation for high resolution SIMS imaging and the limiting factors of lateral resolution is given. The next section covers the chemical analysis of nanoparticles. Recent applications of nanoscale imaging SIMS in geology, cosmochemistry, materials research, cellular biology, ecology and medical research are summarized and illustrated by examples.
TL;DR: In this article, an ultraviolet (200 nm) femtosecond laser ablation (200FsLA) sector-field inductively coupled plasma mass spectrometry (SF-ICPMS) system was used for major and trace element analyses in anhydrous silicate glasses and minerals.
Abstract: We have tested an ultraviolet (200 nm) femtosecond laser ablation (200FsLA) sector-field inductively coupled plasma mass spectrometry (SF-ICPMS) system for major and trace element analyses in anhydrous silicate glasses and minerals. Use of the 200FsLA minimized the matrix effect by 50% compared to that of a 193 nm nanosecond excimer LA. The origin of this improvement was identified as the suppression of ‘melting point (MP)-induced’ element fractionation at the LA site due to a decreased thermal effect of the 200FsLA. Sensitivity enhancement in elements with high first ionization energy remained for the basalt aerosols relative to silica-rich aerosols. This is interpreted as being due to the higher thermal conductivity of the basalt aerosols in the inductively coupled plasma enhanced ionization, which is essentially controlled by the first ionization energy of an element. This was confirmed by simulation using Saha's equation and by the analytical data after reduction of the MP-induced fractionation at the LA site. Accurate determination of trace elements (within 5% of accepted values) was achieved for MPI-DING glasses ranging from komatiite to rhyolite, using a single basalt glass BHVO-2G as the calibration standard. This method is also applicable to anhydrous silicate minerals such as plagioclase, pyroxenes, and garnet. However, SRM610 glass, which has a very different matrix compared to BHVO-2G, is preferred for zircon. Apart from this exception, the proposed method requires no external analytical techniques when the amounts of unmeasured elements in the materials, such as halogens or water, are negligibly low, which is the case for many geological materials.