| 1. |
- Appelblad, Petra K., et al.
(författare)
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Determination of metal-humic complexes, free metal ions and total concentrations in natural waters
- 1999
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Ingår i: Journal of Environmental Monitoring. - 1464-0325 .- 1464-0333. ; 1:3, s. 211-217
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Tidskriftsartikel (refereegranskat)abstract
- A comparison of two systems for the quantitation of metal-humic complexes and free metal ions, consisting of the separation by coupled ion exchange columns followed by detection by inductively coupled plasma mass spectrometry or cold vapour atomic fluorescence spectrometry, is presented. The systems evaluated comprised the serially coupled anion and cation exchangers, Sephadex A-25/Chelex 100 and Dowex 1X8/Chelamine Metalfix. Separation and preconcentration of the species studied were accomplished with both systems, elution being carried out using 2 M HNO3. Total concentrations, metal-humic complex fractions and free metal ion fractions of Al, Ba, Cd, Co, Cu, Fe, Hg, Mn, Pb, Sr, U and Zn in nine natural waters were determined. Statistical evaluation of the data from the two cation exchange materials, including results for additional elements, showed better precision (for Al, Ba, Cr, Cu and Mo) and higher recoveries (Al, Ba, Cd, Fe, Sr and Zn) for Chelex 100 than Chelamine Metalfix for free metal ions. On the other hand, Chelamine Metalfix recovered a significantly greater amount of Ni. The amounts of metal-humic complexes were compared with modelled distributions of these species, and one advantage of the preferred Sephadex A-25/Chelex 100 system is that the elements studied are all correctly classified with respect to their binding strengths to humic substances, which is not the case with the Dowex 1X8/Chelamine Metalfix pair. With the preferred system, metal-humic complexes can be reliably determined, as indicated by the results of equilibrium speciation modelling. However, comparison with the total concentrations showed statistically significant, non-quantitative recoveries of Al, Cu, Hg, Mn, U and Zn from some samples. Thus a combination of speciation and total concentration measurements is required to obtain a complete representation of the distribution of trace elements in natural waters.
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| 2. |
- Appelblad, Petra K.
(författare)
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Inductively coupled plasma mass spectrometry : fundamental studies
- 2000
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inductively coupled plasma mass spectrometry (ICP-MS) is in focus in this thesis. Fundamental studies of ICP double focusing magnetic sector MS are presented, and some possible applications are discussed. One of the recent innovations for increasing the sensitivity of ICP-MS is to use a Pt-shield inserted between the coil and the torch, which can be grounded. It is known that use of a shielded torch results in gain in sensitivity as well attenuation of the secondary discharge, but other physical parameters change as well. Thereby a thorough study of a torch with a Pt guard electrode has been performed in order to address these questions. Matrix effects from seawater samples are described. Isotope ratio measurements can be performed using ICP-MS. The raw data collected needs to be mathematically corrected for mass discrimination factors as well as detector dead time. A model is presented herein with which both these factors can be determined from calibration curves.
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| 3. |
- 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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| 4. |
- Rodushkin, Ilia, et al.
(författare)
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Multielement determination and lead isotope ratio measurement in alcoholic beverages by high-resolution inductively coupled plasma mass spectrometry
- 1999
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Ingår i: Journal of Food Composition and Analysis. - : Elsevier BV. - 0889-1575 .- 1096-0481. ; 12:4, s. 243-257
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Tidskriftsartikel (refereegranskat)abstract
- The analytical performance of inductively coupled plasma mass spectrometry (ICP-MS) for the inorganic analysis of alcoholic beverages was evaluated using double-focusing sector field ICP-MS (ICP-SMS). No sample pre-treatment other than acidification and dilution was carried out. Though aspiration of ethanol-containing solutions into the ICP caused significant matrix effects, accurate results could be obtained by using matrix-matched blanks and standards. Method detection limits reach the fg mL-1range for elements with high m/z ratios which makes the technique especially useful for determination of such low-abundant elements as REE, actinide elements, etc., in this sample type. Between-run reproducibility better than 10% RSD was found for the majority of the elements even at ultra-trace concentrations. The precision in lead isotope ratio measurements is superior to that obtained with quadrupole systems (ICP-QMS) and an uncertainty of about 0.06% RSD can be routinely obtained. Measured ratios for wines of European origin are in good agreement with previously published results obtained by thermal ionization mass spectrometry (TIMS). The robustness of the analytical procedure was tested by analysis of a wide range of alcoholic beverages from the Swedish market. Average elemental concentrations found in wines, whiskies and spiced strong aperitifs are also given.
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| 5. |
- Sjögren, Anna, et al.
(författare)
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Isotope amount ratio measurements by ICP-MS : Aspects of software induced measurement bias and non-linearity
- 2005
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Ingår i: Journal of Analytical Atomic Spectrometry. - 0267-9477 .- 1364-5544. ; 20:4, s. 320-322
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Tidskriftsartikel (refereegranskat)abstract
- The effect of a post-acquisition software induced bias on the measurement of the 235U/238U isotope amount ratio in the reference material IRMM-184 was studied. The total uranium concentration ranged from 7 to 2500 pg g-1 [80 (235U) to 3 500 000 (238U) counts per second], thus covering the entire pulse counting range of the ICP-MS instrument. The bias for the measured ratio increases with decreasing count rate, and it is mostly governed by the count rate of the 235U isotope. Blocking the data into large subgroups is one way of reducing the effects of the bias; however, a decreased number of blocks is accompanied by an increased scattering of the standard uncertainty. Using a more laborious, manual data evaluation procedure of a less processed raw measurement signal not only solves the problem, it also increases the linear measurement range by at least ten times. At the lowest concentration, 7 pg g-1 total uranium concentration, the combined uncertainty of the observed ratio was less than 5% (k = 2).
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