Laser Ablation Inductively Coupled Plasma Mass Spectrometry: Principles and Applications

Abstract

The application of laser ablation inductively plasma mass spectrometry (LA‐ICP‐MS) to the determination of major, minor, and trace elements as well as isotope‐ratio measurements offers superior technology for direct solid sampling in analytical chemistry. The advantages of LA‐ICP‐MS include direct analysis of solids; no chemical dissolution is necessary, reduced risk of contamination, analysis of small sample mass, and determination of spatial distributions of elemental compositions. This review aims to summarize recent research to apply LA‐ICP‐MS, primarily in the field of environmental chemistry. Experimental systems, fractionation, calibration procedures, figures of merit, and new applications are discussed. Selected applications highlighting LA‐ICP‐MS are presented.     

Preliminary in situ teeth study of the narrow‐ridged finless porpoises remains using microsynchrotron radiation X‐ray fluorescence and laser ablation inductively coupled plasma mass spectrometry

In recent years, a growing number of the narrow‐ridged finless porpoises were found dead near the Yangtze River estuary. In this region lived two sympatric subspecies, respectively, the East Asian finless porpoise and the Yangtze finless porpoise. So far, it is difficult to distinguish these two subspecies due to their similar shape and unavailable molecular marker. In this work, synchrotron radiation X‐ray fluorescence (SRXRF) and laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) were applied for in situ teeth trace chemical analysis to study subspecies identification and migration near the Yangtze River estuary. Teeth Sr concentration and ⁸⁷Sr/⁸⁶Sr ratios, determined by SRXRF and LA‐ICP‐MS techniques, have potential application in the identification of the finless porpoise subspecies. Only one (Sample S4) of the six samples was concluded as the Yangtze finless porpoise, and the others were the East Asian finless porpoise. This study also proved that the Sr/Ca and Zn/Ca ratios could be used as a useful environmental indicator to detect the migratory history of narrow‐ridged finless porpoises.     

Quantitative determination of essential and trace element content of medicinal plants and their infusions by XRF and ICP techniques

Macro‐ and microelement contents of five medicinal plants (Taraxacum officinale Weber, Eucalyptus globulus Labill, Plantago lanceolata L., Matricaria chamomilla L. and Mentha piperita L.) and their infusions were evaluated by the combined use of x‐ray fluorescence (WDXRF and EDXRF, bulk raw plants) and inductively coupled plasma (ICP‐MS and ICP‐AES, infusions) techniques. The analytical methods allow the determination of 17 elements (Na, Mg, Al, Si, P, S, K, Ca, Ti, Mn, Fe, Cu, Zn, As, Rb, Sr, and Pb) both in plants and in the infusions. The use of XRF techniques offer a good multielemental approach for the rapid quality control of bulk raw plant materials whereas ICP techniques are well suited for the analytical control of infusions in order to ascertain the nutritional role of medicinal plants and the daily dietary intake. Copyright © 2005 John Wiley & Sons, Ltd.     

Methodology for the determination of minor and trace elements in petroleum cokes by wavelength‐dispersive X‐ray fluorescence (WD‐XRF)

This article describes a methodology for the analysis of minor and trace elements in petroleum cokes by wavelength‐dispersive X‐ray fluorescence (WD‐XRF) spectrometry. The methodology was developed in order to have a rapid and reliable control method of these elements, because they determine coke end uses. There are a number of standard methods of chemical analysis by WD‐XRF or inductively coupled plasma atomic emission spectrometry (ICP‐OES) techniques. However, the standards that use WD‐XRF measurement give detection limits (L_D) above 10 mg·kg^?1 and only analyse a few elements of interest, whereas the ICP‐OES method requires extensive sample handling and long sample preparation times, with the ensuing errors. In order to improve the method described in the standard ASTM D6376 and reach the L_D and quantification limits (L_Q) required, the different stages of the process, ranging from sample preparation to measurement conditions: analytical line, detector, crystal, tube power, use of primary beam filters, and measurement time, were optimised. The samples were prepared in the form of pressed pellets, under conditions of high cleanliness of the mills, crushers, presses, and dies, and of the laboratory itself. The following reference materials were used in measurement calibration and validation: SRM 1632c, SRM 2718, SRM 2719, SRM 2685b, AR 2771, AR 2772, SARM 18, SARM 19, and CLB‐1. In addition, a series of materials were analysed by WD‐XRF and ICP‐OES, and the results were compared. The developed methodology, which uses WD‐XRF, is rapid and accurate, and very low L_D and measurement uncertainties were obtained for the following elements: Al, Ba, Ca, Cr, Cu, Fe, Ge, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, V, and Zn. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparison of trace elements analysis of nephrite samples from different deposits by PIXE and ICP‐AES

Comparing values of trace elements determined by external‐beam proton‐induced X‐ray emission (PIXE) and inductively coupled plasma atomic emission spectrometry (ICP‐AES) is important to find the provenience of raw materials of ancient nephrite artifacts, because most previous elemental characterizations of nephrite minerals were obtained by ICP‐AES, but PIXE presents the possibility of nondestructive analysis for largely and integrally ancient nephrite artifacts. In this work based on 12 nephrite minerals, it shows that the distribution of trace elements of nephrite samples both in PIXE and ICP‐AES data are generally consistent, although large differences exist in some elements. According to the trace elements, the two types of nephrite mineralization origins can be distinguished, determined by PIXE and ICP‐AES, respectively. Moreover, depending on the PIXE and ICP‐AES data, Sr can be regarded as fingerprint element of Xiaomeiling nephrite minerals, and the differentiation of Sr content between Xiaomeiling nephrite minerals and ancient nephrite artifacts from Liangzhu culture (3300–2300 bc ) is clear evidence that the raw materials of the artifacts are not from Xiaomeiling deposit. The nephrite minerals from Wenchuan deposit can be distinguished from other samples because of their high values of Mn/Fe. Therefore, the PIXE can be used with ICP‐AES to judge mineralization mechanism and find fingerprint elements of raw materials of ancient nephrite artifacts. Copyright © 2012 John Wiley & Sons, Ltd.     

Elemental characterization of edible plants and soils in an abandoned mining region: assessment of environmental risk

The chemical concentrations of 11 elements in 6 species of edible plants grown in 7 soils, developed in different gossanous materials of the abandoned mine area of Sao Domingos, in southern Portugal, was measured by energy dispersive X‐ray fluorescence. The total fraction of elements in the soils from which the plants were sampled, was measured, using wavelength dispersive X‐ray fluorescence. The elemental content in bioavailable fraction was obtained by using three different leaching tests: DIN 38414‐S4, 1 M ammonium acetate and 0.005 M DTPA. Leachates were analyzed by Induced Coupled Plasma—Optical Emission Spectrometer (ICP‐OES) and Induced Coupled Plasma—Mass Spectrometer (ICP‐MS). The mineralogy of the same soils was evaluated by X‐ray diffraction to identify the species present. The results show that levels in plants can be hazardous especially for Pb and As. Important concentrations of Fe and K were also observed. A different uptake was observed in the several plants for the different elements. The highest assimilation of metals was observed in sampling points containing soluble sulfate salts. Copyright © 2011 John Wiley & Sons, Ltd.     

Plant elemental composition and portable X‐ray fluorescence (pXRF) spectroscopy: quantification under different analytical parameters

Emergence of portable X‐ray fluorescence (pXRF) systems presents new opportunities for rapid, low‐cost plant analysis, both as a lab system and in situ system. Numerous studies have extolled the virtues of using pXRF for a wide range of plant applications, however, for many such applications, there is need for further assessment with regards to analytical parameters for plant analysis. While pXRF is a potential powerful research tool for elemental composition analysis, its successful use in plant analysis is made more likely by having an understanding of X‐ray physics, calibration process, and ability to test a variety of homogenous and well‐characterized materials for developing a matrix‐specific calibration. Because potential pXRF users may often underestimate the complexity of proper analysis, this study aims at providing a technical background for plant analysis using pXRF. The focus is on elemental quantification under different analytical parameters and different methods of sample presentation: direct surface contact under vacuum, placement in a sample cup with prolene as a seal, and without the aid of a vacuum. Direct analysis on the surface of a pXRF provided highest sensitivity and accuracy (R² > 0.90) for light elements (Mg to P). Sulfur, K, and Ca can be reliably measured without the aid of a vacuum (R² > 0.99, 0.97, and 0.93 respectively), although lower detection limits may be compromised. pXRF instruments provide plant data of sufficient accuracy for many applications and will reduce the overall time and budget compared with the use of conventional techniques. Sensitivity and accuracy are dependent on the instrument's settings, make, and model. © 2015 The Authors. X‐Ray Spectrometry published by John Wiley & Sons, Ltd.     

An integrated spectroscopic approach to investigate pigments and engobes on pre‐Roman pottery

Painted Canosa ceramics were examined to identify the nature of the pigments employed and their manufacturing technology. A multi‐technique approach was used, comprising Raman microspectroscopy and laser ablation hyphenated to inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS). The analysed samples were mainly produced for burial in tombs and were not intended for everyday use. They belong to the period between the end of the mid‐7th century and the first half of the 4th century BC, and were excavated from the Toppicelli archaeological district near the suburbs of Canosa (Puglia, Italy). Forty‐eight pottery fragments were available for this study. No handling of the samples was required for the Raman study, and it was possible to excise the pigmented layer in such a way that the lacunae were not distinguishable to the naked eye due to the micrometric size of the laser spot as far as LA‐ICP‐MS is concerned. Their combination turned out to be quite useful for the investigation of these archaeological materials: the chemical nature of the white, red, brown and black pigments employed in the pottery manufacture was investigated. Iron and manganese compounds were identified as the red and brown/black main colouring substances, respectively; on the other hand, whites and engobes (whitish slips) were based on kaolinite. This set of colouring substances is of importance, as it enabled the artisan to obtain in one oxidising firing cycle brown, black and red paints. Finally, the finding of manganese black in these Canosa potsherds confirms that Canosa was an important centre connecting the near East to central Italy and Europe since the pre‐Roman age. Copyright © 2010 John Wiley & Sons, Ltd.     

Monte Carlo simulation code for confocal 3D micro‐beam X‐ray fluorescence analysis of stratified materials

Stratified materials are of great importance for many branches of modern industry, e.g. electronics or optics and for biomedical applications. Examination of chemical composition of individual layers and determination of their thickness helps to get information on their properties and function. A confocal 3D micro X‐ray fluorescence (3D µXRF) spectroscopy is an analytical method giving the possibility to investigate 3D distribution of chemical elements in a sample with spatial resolution in the micrometer regime in a non‐destructive way. Thin foils of Ti, Cu and Au, a bulk sample of Cu and a three‐layered sandwich sample, made of two thin Fe/Ni alloy foils, separated by polypropylene, were used as test samples. A Monte Carlo (MC) simulation code for the determination of elemental concentrations and thickness of individual layers in stratified materials with the use of confocal 3D µXRF spectroscopy was developed. The X‐ray intensity profiles versus the depth below surface, obtained from 3D µXRF experiments, MC simulation and an analytical approach were compared. Correlation coefficients between experimental versus simulated, and experimental versus analytical model X‐ray profiles were calculated. The correlation coefficients were comparable for both methods and exceeded 99%. The experimental X‐ray intensity profiles were deconvoluted with iterative MC simulation and by using analytical expression. The MC method produced slightly more accurate elemental concentrations and thickness of successive layers as compared to the results of the analytical approach. This MC code is a robust tool for simulation of scanning confocal 3D µXRF experiments on stratified materials and for quantitative interpretation of experimental results. Copyright © 2011 John Wiley & Sons, Ltd.     

Acid assisted proton transfer in 4‐[(4‐R‐phenylimino)methyl]pyridin‐3‐ols: NMR spectroscopy in solution and solid state,X‐ray and UV studies and DFT calculations

The behaviour of Schiff bases of 3‐hydroxy‐4‐pyridincarboxaldehyde and 4‐R‐anilines (R?H, CH₃, OCH₃, Br, Cl, NO₂) in acid media has been described. ¹H, ¹³C, ¹⁵N‐NMR chemical shifts allow to establish the protonation site and its influence on the hydroxyimino/oxoenamino tautomerism. DFT calculations, electronic spectra and X‐ray diffraction are in agreement with the NMR conclusions. Copyright © 2007 John Wiley & Sons, Ltd.     

A portable spectrometer for simultaneous PIXE and XRF analysis

A new portable system that performs simultaneous particle induced x‐ray emission and x‐ray fluorescence analysis is described. It is based on the use of a ²⁴⁴Cm radioactive source as α‐particle and x‐ray emitter, coupled to a Si drift detector. Particular care has been devoted to the choice of the materials surrounding the source. X‐ray fluorescence spectra are presented, showing high detection efficiency for elements from Na (K lines) to Pb (L and M lines). The system can be used as a qualitative tool for ‘fingerprint’ analysis and, in some cases, as a quantitative one. Examples are presented and discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Application of Multivariate Techniques in Optimization of Spectroanalytical Methods

Abstract

The present article describes fundamentals and applications of multivariate techniques used for the optimization of analytical procedures and systems involving spectroanalytical methods such as flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively coupled plasma mass spectrometry (ICP‐MS), considering the main steps of a chemical analysis. This way, applications of experimental designs in optimization of sampling systems, digestion procedures, preconcentration procedures, instrumental parameters of quantification steps of analytical methods, and robustness tests have been summarized in this work.     

Physical parameters for atomic inner‐shell photoionization processes and analytical applications: a status report

The atomic inner‐shell vacancy decay processes comprising of radiative and non‐radiative transitions are characterized by the physical parameters, namely, the photoionization cross‐sections; X‐ray, Auger and Coster–Kronig (CK) transition rates; fluorescence and CK yields; and the vacancy transfer probabilities. These parameters are required to calculate the K‐shell and L_i (i = 1–3)/M_i (i = 1–5) sub‐shell X‐ray production cross‐sections and relative intensities which, in turn, are needed for different analytical applications. This report intended to provide a detailed account of the currently available data sets of different physical parameters for use in various analytical applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Elemental analysis of particulate matter in a metal workshop and of biological samples from exposed workers

During metal welding and cutting, large amounts of particulate matter (PM) are produced that might represent a significant health risk for the exposed workers. In the present pilot study, we performed an elemental analysis of fine PM collected in a metal workshop. Also, elemental analysis of the hair and nail samples collected from workers exposed to the workshop dust and control group was done. Concentrations of 15 elements in PM were measured with X‐Ray Fluorescence (XRF) and Particle Induced X‐ray Emission (PIXE), whereas inductively coupled plasma mass spectrometry (ICP‐MS) was used to determine 12 elements in hair and nail samples. Mean 8‐hr concentrations of PM_2.5, Fe, and Mn in the vicinity of welders were up to 1803, 860, and 30 μg/m³, respectively, whereas in the nearby city, daily PM_2.5 concentrations are on average 11 μg/m³. We found that several elements, especially Fe and Mn, had substantially higher concentrations in hair and nail samples of exposed workers than in the control group, which indicates the accumulation of metals in workers' tissues, although limit values were not exceeded.     

Patterns of inter‐elemental effects in EDXRF and a new correction method

A new method is suggested for improving the accuracy of energy‐dispersive x‐ray fluorescence analysis (EDXRF) and its implementation is described. This method is a result of studying changes in coefficients of the inter‐elemental effect, A = f(Z). We created a data bank for elements from K to Br, which accounts for the effect of three lighter and five heavier neighboring elements upon the sought element. This study offers a physical explanation of sharp bends in coefficient curves. We suggest principles for optimizing the analytical region parameters so as to reduce the effect of neighboring elements. Finally, we describe the principles of building a data bank A = f(Z, R) to account for the effect of energy resolution (R) change. Application of the suggested method to the exploration of oceanic nodules reduced the cobalt detection threshold by 50–75% (C_lim?0.95 = 0.032%) and decreased the standard deviation of spectrum analysis, thus enhancing confidence in EDXRF as an effective tool for research on complex objects. The approach suggested in this study can be used with newer energy‐dispersive analyzers, including TXRF models. Copyright © 2003 John Wiley & Sons, Ltd.     

X‐ray photon correlation spectroscopy in systems without long‐range order: existence of an intermediate‐field regime

Successful X‐ray photon correlation spectroscopy studies often require that signals be optimized while minimizing power density in the sample to decrease radiation damage and, at free‐electron laser sources, thermal impact. This suggests exploration of scattering outside the Fraunhofer far‐field diffraction limit d²/λR, where d is the incident beam size, λ is the photon wavelength and R is the sample‐to‐detector distance. Here it is shown that, in an intermediate regime d²/λ > Rdξ/λ, where ξ is the structural correlation length in the material, the ensemble averages of the scattered intensity and of the structure factor are equal. Similarly, in the regime d²/λ > Rdξ(τ)/λ, where ξ(τ) is a time‐dependent dynamics length scale of interest, the ensemble‐averaged correlation functions g₁(τ) and g₂(τ) of the scattered electric field are also equal to their values in the far‐field limit. This broadens the parameter space for X‐ray photon correlation spectroscopy experiments, but detectors with smaller pixel size and variable focusing are required to more fully exploit the potential for such studies.     

Total reflection x‐ray fluorescence analysis—a review

Total reflection x‐ray fluorescence analysis (TXRF) is a special energy‐dispersive x‐ray analytical technique extending XRF down to the ultra trace element range. Detection limits of picograms or nanograms per gram levels are reached with x‐ray tube excitation. Using synchrotron radiation as excitation source, femtogram levels are detectable, particularly important for Si wafer surface analysis. TXRF is specially suited for applications in which only a very small amount of sample is available, as only a few micrograms are required for the analysis. In this review, an overview of theoretical principles, advantages, instrumentation, quantification and application is given. Chemical analysis as well as surface analysis including depth profiling and thin‐film characterization is described. Special research results on extension to low‐Z elements, excitation with synchrotron radiation and x‐ray absorption spectroscopy (XAS) for chemical speciation at trace levels are reviewed. Copyright © 2007 John Wiley & Sons, Ltd.     

Comparison of Inductively Coupled Plasma with Classical Analytical Techniques in the Analysis of Southern Oregon Lithia Water: Inclusion of a Local Resource in the Undergraduate Chemistry Curriculum

Abstract

Lithia water, a community resource of local historical significance, is described as a central theme in the undergraduate analytical chemistry sequence. A statistical comparison of the classical determination of major cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) and anions (HCO₃ ^?, Cl^?) reinforces statistical and charge‐balance concepts covered in analytical chemistry. Subsequent determination of these major cations by inductively coupled plasma (ICP) enables students to statistically evaluate the presence of bias between instrumental and classical methods. The effect of easily ionized elements on ICP calibration sensitivity and linearity via the use of cesium as an ionization suppressor is reported.     

Application of high‐energy polarized energy‐dispersive x‐ray fluorescence spectrometry to the determination of trace levels of As,Hg, and Pb in certifiable color additives

Advances in x‐ray fluorescence (XRF) using high‐energy polarized energy‐dispersive (ED)XRF spectrometry (PEDXRF) were applied to the determination of trace As, Hg, and Pb in various color additives subject to batch certification by the U.S. Food and Drug Administration (FDA). The objectives of this study were to simplify sample preparation for quantitative determination of these elements and, if possible, to achieve improved sensitivity and detection limits compared to techniques currently used for certification. PEDXRF was compared with wavelength‐dispersive x‐ray fluorescence spectrometry (WDXRF) and inductively coupled plasma – mass spectrometry (ICP‐MS) for the analysis of trace levels of As, Hg, and Pb in certifiable color additives. For these light matrices, PEDXRF provided better signal‐to‐noise and allowed quantitation in smaller amounts of color additive relative to WDXRF and equal or better precision to ICP‐MS. Determination of these trace elements in a variety of color additives was possible relative to calibrations generated from one color additive using specimens prepared simply by pouring the color additive powder into an XRF sample cup. Published 2016. This article is a U.S. Government work and is in the public domain in the USA     

Extraction of local coordination structure in a low‐concentration uranyl system by XANES

Obtaining structural information of uranyl species at an atomic/molecular scale is a critical step to control and predict their physical and chemical properties. To obtain such information, experimental and theoretical L₃‐edge X‐ray absorption near‐edge structure (XANES) spectra of uranium were studied systematically for uranyl complexes. It was demonstrated that the bond lengths (R) in the uranyl species and relative energy positions (ΔE) of the XANES were determined as follows: ΔE₁ = 168.3/R(U—O_ax)² ? 38.5 (for the axial plane) and ΔE₂ = 428.4/R(U—O_eq)² ? 37.1 (for the equatorial plane). These formulae could be used to directly extract the distances between the uranium absorber and oxygen ligand atoms in the axial and equatorial planes of uranyl ions based on the U L₃‐edge XANES experimental data. In addition, the relative weights were estimated for each configuration derived from the water molecule and nitrate ligand based on the obtained average equatorial coordination bond lengths in a series of uranyl nitrate complexes with progressively varied nitrate concentrations. Results obtained from XANES analysis were identical to that from extended X‐ray absorption fine‐structure (EXAFS) analysis. XANES analysis is applicable to ubiquitous uranyl–ligand complexes, such as the uranyl–carbonate complex. Most importantly, the XANES research method could be extended to low‐concentration uranyl systems, as indicated by the results of the uranyl–amidoximate complex (～40 p.p.m. uranium). Quantitative XANES analysis, a reliable and straightforward method, provides a simplified approach applied to the structural chemistry of actinides.