| 1. |
- Pallavicini, Nicola, et al.
(författare)
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Ranges of B, Cd, Cr, Cu, Fe, Pb, Sr, Tl, and Zn Concentrations and Isotope Ratios in Environmental Matrices from an Urban Area
- 2018
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Ingår i: Journal of Spectroscopy. - : Hindawi Publishing Corporation. - 2314-4920 .- 2314-4939. ; , s. 1-17
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Tidskriftsartikel (refereegranskat)abstract
- Isotopic information may provide powerful insight into the elemental cycling processes which occur in natural compartments. Further implementation of isotopic techniques in natural sciences requires a better understanding of the range of elemental and isotopic compositional variability in environmental matrices. This study assesses the local-scale concentration and isotopic composition variability of nine elements: boron (B), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), strontium (Sr), thallium (Tl), and zinc (Zn) in lysimetric waters, mushrooms, litter, needles, leaves, and lichens. Sequential extractions were also performed on soil samples from 6 depth profiles providing more detailed information on the variability of elemental concentrations and isotope ratios between the elemental pools present in soil. For most of the sample types studied the range of isotopic variability between samples spans almost the entire ranges reported in the literature for natural samples. These results represent a starting point for discussing the role of natural variability in isotopic studies (for example, as a limiting factor in the use of isotopic mixing models) and a baseline for future in-depth studies examining the controls on isotope fraction in natural systems
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| 2. |
- Rodushkin, Ilia, et al.
(författare)
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Application of double-focusing sector field ICP-MS for determination of ultratrace constituents in samples characterized by complex composition of the matrix
- 2018
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Ingår i: Science of the Total Environment. - : ELSEVIER SCIENCE BV. - 0048-9697 .- 1879-1026. ; 622-623, s. 203-213
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Tidskriftsartikel (refereegranskat)abstract
- The performance of double focusing, sector fieldmass spectrometry (ICP-SFMS) for determination of analytes, including technology critical elements (TCE), at ultra-trace levels in environmental and clinical matrices was critically evaluated. Different configurations of the ICP-SFMS introduction system as well as various sample preparations, pre-concentration andmatrix separation methods were employed and compared. Factors affecting detection capabilities and accuracy of data produced (instrumental sensitivity, contamination risks, purity of reagents, spectral interferences, matrix effects, analyte recovery and losses) were discussed. Optimized matrixspecific methods were applied to a range of reference and control materials (riverine, brackish and seawaters; whole blood, serumand urine) as well as tap water and snow samples collected in the area of Lulea city, northern Sweden; brackish and seawater from the Laptev Sea; venous blood samples with a special emphasis on determination of Au, Ag, Ir, Os, Pd, Pt, Re, Rh, Ru, Sb and Te. Even though these low abundant elements are relatively under-documented, the results produced were compared with published data, where available.
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| 3. |
- Andren, Henrik, et al.
(författare)
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Sources of mass bias and isotope ratio variation in multi-collector ICP-MS : optimization of instrumental parameters based on experimental observations
- 2004
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 19:9, s. 1217-1224
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Tidskriftsartikel (refereegranskat)abstract
- In this work, several contributing factors to the observed mass bias in inductively coupled plasma mass spectrometry (ICP-MS) have been identified. Analyses of the isotopic compositions of B deposited on sampler and skimmer cones demonstrate enrichment of [1][0]B on the former and [1][1]B on the latter. Grounding the capacitive discharge system to enhance sensitivity also magnified the level of [1][1]B enrichment on the skimmer cone more than four-fold. This supersonic expansion of the ion beam behind the sampler is confirmed to be an important source of mass bias. Isotopic analyses of the Fe, Zn and Ti leached from used extraction lenses yielded a linear relationship between the levels of lighter isotope depletion and mass ratio. Although consistent with the space-charge effect, the fact that isotopically-heavy deposits were found demonstrates that the ion beam diverges into a relatively wide solid angle in the field-free region behind the skimmer. This severely impairs transmission of, in particular, the lighter isotopes. For a wide range of elements (Li, B, Fe, Ni, Cu, Sb, Ce, Hf and Re), the magnitude of the mass bias was found to be affected by the sample gas flow rate, as well as the distance between the sampler and the end of the torch, i.e., the sampling depth, employed in the Neptune multi-collector ICP-MS instrument. Mathematical analysis of the profiles of intensity variations as a function of these instrumental parameters revealed that the response peaks closer to the torch for the heavier isotopes of all studied elements. Owing to this spatial non-coincidence, tuning for maximum intensity on either isotope will result in sampling from a region where even slight plasma instabilities will be translated into substantial variations in mass bias. Therefore, in-plasma processes also contribute to the degree and temporal stability of mass bias. In light of these findings, recommendations for optimizing multi-collector ICP-MS with respect to obtaining the highest possible precision are presented.
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| 4. |
- Andren, Henrik, et al.
(författare)
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Variations in instrumental mass discrimination
- 2004
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Ingår i: 2004 Winter Conference on Plasma Spectrochemistry. - Cambridge : Royal Society of Chemistry. ; , s. 329-
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Konferensbidrag (refereegranskat)
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| 5. |
- Appelblad, P.K., et al.
(författare)
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Sources of uncertainty in isotope ratio measurements by inductively coupled plasma mass spectrometry
- 2001
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 73:13, s. 2911-2919
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Tidskriftsartikel (refereegranskat)abstract
- A model is presented describing the effects of dead time and mass bias correction factor uncertainties, flicker noise, and counting statistics on isotope ratio measurement precision using inductively coupled plasma mass spectrometry (ICPMS) with a single collector. Noise spectral analysis is exploited to enable estimation of the flicker noise parameters. For the instrument used, the flicker noise component exhibited a fairly weak frequency (f) dependence ( f -0.33±0.12), but was directly proportional to the total number of counts, Q. As white noise, determined by counting statistics, is given by Q0.5, the isotope ratio measurement uncertainties will actually cease to improve when Q exceeds a certain threshold. This would suggest that flicker noise could become the limiting factor for the precision with which isotope ratios can be determined by ICPMS. However, under most experimental conditions, uncertainties associated with mass discrimination and dead time correction factors are decisive. For ratios up to ~22 (115In/113In), optimum major isotope count rates are generally below 0.3 MHz, for which precision in the mass discrimination factor is limiting. The model derived could be used as a starting point for determining optimum conditions and understanding the limitations of single-collector ICPMS for precise isotope ratio measurements.
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| 6. |
- Appelblad, Petra K., et al.
(författare)
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The use of Pt guard electrode in inductively coupled plasma sectorÆeld mass spectrometry: advantages and limitations
- 2000
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 15:4, s. 359-364
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Tidskriftsartikel (refereegranskat)abstract
- Performance characteristics of inductively coupled plasma sector field mass spectrometry (ICP-SFMS) were studied with a Pt guard electrode (GE) inserted between the torch and load coil. The importance of the optimisation procedure and the matrix effects caused by a seawater matrix were assessed for 20 elements. Oxide and doubly charged ion formation was also investigated. Use of the GE allows a significant increase in ion transmission, by a factor of three to 20, thus resulting in improved instrumental detection limits. The improvement in sensitivity is mass dependent, with the highest gain observed for lower mass elements. Since, for the majority of analytical applications, actual detection limits depend upon blank levels rather on instrumental sensitivity, the most important factor for the determination of elements at ultra-trace levels is the degree of contamination of reagents and containers used. At the same time, significantly greater oxide formation is observed when operating the GE grounded rather than in the floating mode. For example, the BaO+/Ba+ ratio is ten to twelve times higher in the grounded mode. This calls for compromised instrumental parameters and the potential for severe spectral interferences from oxide species, which are often unresolved, even in high-resolution mode. Furthermore, non-spectral interferences from the seawater matrix appear to be more pronounced with the grounded GE, yielding a recovery of Ni of 55% compared with 93% in the floating GE mode. Hence all possible advantages and limitations of the use of the GE should be carefully considered prior to the analysis of real samples.
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| 7. |
- Axelsson, Mikael D., et al.
(författare)
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High spatial resolution analysis of ferromanganese concretions by LA-ICP-MS
- 2002
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Ingår i: Geochemical Transactions. - : Springer Science and Business Media LLC. - 1467-4866. ; 3:5, s. 40-47
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Tidskriftsartikel (refereegranskat)abstract
- A procedure was developed for the determination of element distributions in cross-sections of ferromanganese concretions using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The effects of carrier flow rates, rf forward power, ablation energy, ablation spot size, repetition rate and number of shots per point on analyte intensity were studied. It is shown that different carrier gas flow rates are required in order to obtain maximum sensitivities for different groups of elements, thus complicating the optimisation of ICP parameters. On the contrary, LA parameters have very similar effects on almost all elements studied, thus providing a common optimum parameter set for the entire mass range. However, for selected LA parameters, the use of compromise conditions was necessary in order to compensate for relatively slow data acquisition by ICP-MS and maintain high spatial resolution without sacrificing the multielemental capabilities of the technique. Possible variations in ablation efficiency were corrected for mathematically using the sum of Fe and Mn intensities. Quantification by external calibration against matrix-matched standards was successfully used for more than 50 elements. These standards, in the form of pressed pellets (no binder), were prepared in-house using
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| 8. |
- Baxter, Douglas, et al.
(författare)
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Methylmercury measurement in whole blood by isotope-dilution GC-ICPMS with 2 sample preparation methods
- 2007
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Ingår i: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 53:1, s. 111-116
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Tidskriftsartikel (refereegranskat)abstract
- Background: Despite its known toxicity, methylmercury is rarely measured directly in clinical studies; instead, conclusions are based on total mercury measurements. We have developed isotope-dilution-based methods for methylmercury-specific analysis of whole blood by coupled gas chromatography-inductively coupled plasma mass spectrometry (GC-ICPMS). Methods: We analyzed animal and human blood samples after alkaline digestion or extraction of methylmercury into dichloromethane and back extraction into water. Methylmercury was converted to the volatile ethyl derivative, purged, and trapped on a solid-phase collection medium, and then introduced into the GC-ICPMS system. Results: Limits of quantification were 0.4 and 0.03 mu g/L at a signal-to-noise ratio of 10 with the alkaline digestion and extraction methods, respectively. Extraction met our selected acceptable total error criterion, with an SD of 0.58 mu g/L at the critical maternal blood concentration of 5.8 mu g/L.Results obtained with alkaline digestion indicated the need for improved random analytical uncertainty, which was achieved by increasing the enrichment of the isotope dilution. For 37 blood samples, the mean (SD) proportion of total mercury present as methylmercury was 60 (27)%, range 6%-100%.Conclusions: The combination of extraction and isotope-dilution GC-ICPMS meets the requirements for use as a reference method for measuring methylmercury in whole blood.
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| 9. |
- Baxter, Douglas, et al.
(författare)
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Revised exponential model for mass bias correction using an internal standard for isotope abundance ratio measurements by multi-collector inductively coupled plasma mass spectrometry
- 2006
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 21:4, s. 427-430
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Tidskriftsartikel (refereegranskat)abstract
- An internal standard (IS) can be used to account for moderate, matrix-related shifts in mass bias using multi-collector inductively coupled plasma mass spectrometry through the empirical, linear relationship between measured isotope abundance ratios for different elements in ln-ln space. Unfortunately, erroneous mass bias corrected isotope abundance ratios may be returned by the model, requiring artificial adjustment of the true isotope abundance ratio of the IS. Although inadequate correction for peak tailing has been convincingly used to explain this problem, our analysis of the literature describing the development of the mass bias correction model using an IS reveals the presence of a source of systematic error. The origin of this error is purely mathematical and is eliminated in the revised model presented, in which mass bias corrected isotope abundance ratios are independent of the isotopic composition of the IS. An expression for computing the total combined uncertainty in the corrected ratio, incorporating contributions from the linear model, the isotopic reference material, and measurements of analyte element and IS in the sample, is also derived.
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| 10. |
- Baxter, Douglas, et al.
(författare)
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Serum/plasma methylmercury determination by isotope dilution gas chromatography : inductively coupled plasma mass spectrometry
- 2011
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 701:2, s. 134-138
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Tidskriftsartikel (refereegranskat)abstract
- A method for the determination of methylmercury in plasma and serum samples was developed. The method uses isotope dilution with 198Hg-labelled methylmercury, extraction into dichloromethane, back-extraction into water, aqueous-phase ethylation, purge and trap collection, thermal desorption, separation by gas chromatography, and mercury isotope specific detection by inductively coupled plasma mass spectrometry. By spiking 2 mL sample with 1.2 ng tracer, measurements in a concentration interval of (0.007–2.9) μg L−1 could be performed with uncertainty amplification factors <2. A limit of quantification of 0.03 μg L−1 was estimated at 10 times the standard deviation of concentrations measured in preparation blanks. Within- and between-run relative standard deviations were <10% at added concentration levels of 0.14 μg L−1, 0.35 μg L−1 and 2.8 μg L−1, with recoveries in the range 82% to 110%. Application of the method to 50 plasma/serum samples yielded a median (mean; range) concentration of methylmercury of 0.081 (0.091; <0.03–0.19) μg L−1. This is the first time methylmercury has been directly measured in this kind of specimen, and is therefore the first estimate of a reference range.
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