| 1. |
- 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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| 2. |
- 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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| 3. |
- Appelblad, Petra, et al.
(författare)
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Model for calculating dead time and mass discrimination correction factors from inductively coupled plasma mass spectrometry calibration curves
- 2000
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 15:5, s. 557-560
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Tidskriftsartikel (refereegranskat)abstract
- A model allowing simultaneous determination of the detector dead time and the mass discrimination factor in inductively coupled plasma mass spectrometry (ICP-MS), as well as the corresponding uncertainties, is presented and compared for three representative isotope systems, namely magnesium, indium and thallium. The advantages of using the model presented are firstly that both the detector dead time and the mass discrimination factor can be obtained simultaneously and secondly that the sampling time can be spent entirely on the isotopes of interest.
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| 4. |
- Baxter, Douglas, et al.
(författare)
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Isotope abundance ratio measurements by inductively coupled plasma-sector field mass spectrometry
- 2012
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Ingår i: Journal of Analytical Atomic Spectrometry. - 0267-9477 .- 1364-5544. ; 27:8, s. 1355-1381
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Tidskriftsartikel (refereegranskat)abstract
- This tutorial reviews fundamental aspects of isotope abundance ratio measurement by inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). After a synopsis of the scope of isotope abundance ratio measurement and a summary introduction to the factors affecting precision and accuracy, attention is turned to noise sources. Detailed theory behind Poisson or counting statistics and plasma flicker noise components is given, since much of the observed imprecision can be attributed to these sources. Using single collector instruments, ion beams from different isotopes are sampled in rapid sequence, and so ratioing of the signals will be subject to fluctuations derived from intensity variations, i.e., flicker noise. It is demonstrated that flicker noise can, under specified circumstances, become the limiting factor for the attainable precision. Furthermore, the practice of partitioning dwell times, ostensibly to optimize precision based on isotopic abundances and assumed Poisson statistics, is shown to be flawed and actually requires accounting for flicker noise. In addition to random uncertainty, various offset factors may contribute to systematic error in measured isotope abundance ratios. Two of these, namely mass scale shift and spectral interferences are ameliorated using ICP-SFMS. The former is eliminated when operating under conditions providing flat-topped peaks, such that the minor drift in mass calibration typical of the technique becomes inconsequential and the intensity remains the same. Isotope abundance ratio measurements are subject to three further important offset factors. First is abundance sensitivity, which quantifies the extent of peak tailing to neighboring masses and can present a considerable source of offset. Second is mass bias, resulting from the fact that all sector field devices exhibit increasing sensitivity with ion mass, and various empirical methods used to correct for this effect are compared and contrasted. Third is detector dead time, which affects mass spectrometers equipped with ion counting systems. Although a well-understood phenomenon, all current methods for determining the dead time on the basis of experimentally measured isotope abundance ratios are likely to yield biased estimates. Finally, the capabilities of ICP-SFMS for the determination of isotope abundance ratios are placed in perspective by making a brief comparison with other techniques.
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| 5. |
- 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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| 6. |
- Björn, Erik, et al.
(författare)
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Calibration errors due to variations in peak characteristics in the measurement of transient signals by inductively coupled plasma-scanning mass spectrometry
- 2002
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Ingår i: Journal of Analytical Atomic Spectrometry. - 0267-9477 .- 1364-5544. ; 17:12, s. 1582-1588
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Tidskriftsartikel (refereegranskat)abstract
- The impact of variations in peak characteristics on the fidelity of transient signal measurement by inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) was investigated. Specifically, the question as to whether the multi-element capabilities or the accuracy in determined analyte amounts were deteriorated compared to what has been reported previously when not considering peak variations was addressed. The peak characteristics considered were the time of the signal maximum (tpeak), the standard deviation of the assumed Gaussian input function generated by the sample introduction system (σG), and the time constant for signal decay (τ). Investigations of simulated exponentially-modified Gaussian peaks revealed that, for variations of peak characteristics within reasonable ranges, measurement noise and variations in tpeak, σG and τ all contributed to calibration uncertainty. Electrothermal vaporisation (ETV) and flow injection (FI) systems were used to experimentally generate transient signals of varying peak characteristics. Removing data points from the raw signals simulated the monitoring of up to 100 mass-to-charge ratios, allowing calibration data and analyte amounts to be determined from the processed signals. To obtain calibration graph slopes with relative standard deviations below 1% for the ETV-ICP-QMS system, it was found necessary to acquire 7-24 data points per peak for 50-5 ms dwell times. On this basis, the maximum number of mass-to-charge ratios that could be monitored in a typical ETV-ICP-QMS analysis was 4-10 using dwell times of 50-5 ms. With the FI-ICP-QMS system, variations in the peak characteristics between calibration standards and samples meant that, to obtain less than 3% error in determined analyte amounts, at least 7 or 10 points per peak were required for external and internal standardisation, respectively. It was found that variations in peak characteristics contributed more than measurement noise to the error in determined analyte amounts. In recent studies it has been reported that 3-4 data points per peak are sufficient to accurately monitor a transient if peak variations are not considered, which, for typical ETV signals, would allow the monitoring of 20 mass-to-charge ratios during a single measurement cycle. Thus the results obtained here show that the multi-element capability of ICP-QMS when monitoring transient signals can be severely compromised by such variations.
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| 7. |
- Björn, Erik, et al.
(författare)
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Calibration errors due to variations in peak characteristics in the measurement of transient signals by inductively coupled plasma-scanning mass spectrometry
- 2002
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). ; 17, s. 1582-8
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Tidskriftsartikel (refereegranskat)abstract
- The impact of variations in peak characteristics on the fidelity of transient signal measurement by inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) was investigated. Specifically, the question as to whether the multi-element capabilities or the accuracy in determined analyte amounts were deteriorated compared to what has been reported previously when not considering peak variations was addressed. The peak characteristics considered were the time of the signal maximum (tpeak), the standard deviation of the assumed Gaussian input function generated by the sample introduction system (G), and the time constant for signal decay (). Investigations of simulated exponentially-modified Gaussian peaks revealed that, for variations of peak characteristics within reasonable ranges, measurement noise and variations in tpeak, G and all contributed to calibration uncertainty. Electrothermal vaporisation (ETV) and flow injection (FI) systems were used to experimentally generate transient signals of varying peak characteristics. Removing data points from the raw signals simulated the monitoring of up to 100 mass-to-charge ratios, allowing calibration data and analyte amounts to be determined from the processed signals. To obtain calibration graph slopes with relative standard deviations below 1% for the ETV-ICP-QMS system, it was found necessary to acquire 7–24 data points per peak for 50–5 ms dwell times. On this basis, the maximum number of mass-to-charge ratios that could be monitored in a typical ETV-ICP-QMS analysis was 4–10 using dwell times of 50–5 ms. With the FI-ICP-QMS system, variations in the peak characteristics between calibration standards and samples meant that, to obtain less than 3% error in determined analyte amounts, at least 7 or 10 points per peak were required for external and internal standardisation, respectively. It was found that variations in peak characteristics contributed more than measurement noise to the error in determined analyte amounts. In recent studies it has been reported that 3–4 data points per peak are sufficient to accurately monitor a transient if peak variations are not considered, which, for typical ETV signals, would allow the monitoring of 20 mass-to-charge ratios during a single measurement cycle. Thus the results obtained here show that the multi-element capability of ICP-QMS when monitoring transient signals can be severely compromised by such variations.
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| 8. |
- Björn, Erik, et al.
(författare)
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Non-spectral interference effects in inductively coupled plasma mass spectrometry using direct injection high efficiency and microconcentric nebulisation
- 2001
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Ingår i: JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. - : Royal Society of Chemistry (RSC). ; 16, s. 4-11
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Tidskriftsartikel (refereegranskat)abstract
- Non-spectral interference effects in inductively coupled plasma mass spectrometry (ICP-MS) were investigated for the direct injection high efficiency nebuliser (DIHEN) the large bore DIHEN (LB-DIHEN) and a microconcentric nebuliser (MCN) with a cyclone spray chamber. Interference effects from nitric and sulfuric acid, methanol and sodium nitrate solutions were studied. Eight elements with different ionisation potentials (IP) and atomic masses were monitored at various nebuliser gas flow rates. The processes giving rise to interference effects observed with the DIHEN were investigated by monitoring relative analyte sensitivities at different radial plasma positions. It was found that the average magnitude of interference effects decreased in the order MCN approximate to DIHEN > LB-DIHEN, showing that analytical performance is improved by removing the spray chamber. It is suggested that remaining interference effects observed for the DIHEN are caused by a matrix induced spatial redistribution of the aerosol in the plasma due to differences in droplet. size distribution and density between water and the matrix solutions. In addition, the high plasma solvent load with the DIHEN results in a pronounced negative correlation between relative analyte signal magnitude and IP. For the LB-DIHEN, these effects were smaller, and other element specific interference effects dominated. For the eight elements monitored, element specific interference effects increased in the order MCN < DIHEN < LB-DIHEN. Transient acid effects were also investigated and found to be virtually eliminated by the use of a DIHEN instead of the MCN system. For the latter, stabilisation times of 3-10 mill were necessary when changing the nitric acid concentration between 0.22 and 2.2 mol 1(-1).
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| 9. |
- Blachucki, Wojciech, et al.
(författare)
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A laboratory-based double X-ray spectrometer for simultaneous X-ray emission and X-ray absorption studies
- 2019
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry. - 0267-9477 .- 1364-5544. ; 34:7, s. 1409-1415
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Tidskriftsartikel (refereegranskat)abstract
- X-ray spectroscopy studies are usually performed using synchrotron radiation sources, which offer bright, coherent, energy-tuneable and monochromatic light. However, the application of synchrotron-based Xray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) is directly constrained by the limited, infrequent access to central facilities. With the advent of new technological solutions in the field of X-ray sources, optics and detectors, the development of efficient and compact laboratory X-ray spectroscopy systems is possible. A permanent laboratory-based setup offers the advantages of low cost and easy accessibility and, therefore, more flexibility in the preparation and scheduling of measurements. Herein, we report a laboratory X-ray setup allowing simultaneous XES and XAS measurements. The double von Hamos spectrometer performances are demonstrated by concurrent K beta XES and K-edge XAS measurements done for 3d elements.
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| 10. |
- Bredberg, Anna, et al.
(författare)
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Analysis of manganese and iron in exhaled endogenous particles
- 2014
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Ingår i: Journal of Analytical Atomic Spectrometry. - 0267-9477 .- 1364-5544. ; 29, s. 730-735
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Tidskriftsartikel (refereegranskat)abstract
- Background: Many full-time welders experience some sort of respiratory disorder e.g., asthma, bronchitis and metal fume fever. Thus, welding aerosols are thought to cause airway inflammation. There is a need for markers of welding aerosols in exposure assessments, and as most welding aerosols contain manganese and iron, these metals may possibly be used as an indicator. We have previously developed a novel non-invasive technique to collect endogenous particles in exhaled air (PEx). This study is designed to i) develop a method for analysis of manganese and iron in PEx and ii) investigate whether the manganese and/or iron content of PEx changes after exposure to welding aerosols. Methods: Nine individuals were experimentally exposed to welding fumes. PEx was collected at three time points for each individual; before, after and 24 hour after exposure. Analyses of PEx samples were performed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results: Four out of nine individuals showed an increase in manganese and iron levels after exposure to welding aerosols. The mean manganese and iron concentration increased from,
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