| 1. |
- 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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| 2. |
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| 3. |
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| 4. |
- Goitom, Daniel, et al.
(författare)
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Comparison of aerosol properties and ICP-MS analytical performance of the Vulkan direct injection nebuliser and the Direct Injection High Efficiency Nebuliser
- 2007
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). ; 22, s. 250-7
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Tidskriftsartikel (refereegranskat)abstract
- Monodisperse polymer particles consisting of DVB and styrene-copoly-DVB were successfully synthesized by photoinitiated precipitation polymerization with 2,2'-azobis(2-methylpropionitrile) (AIBN) as initiator. A focused 150 W xenon short arc lamp was used to radiate the sample mixtures. The size of the particles ranged from 1.5 to 4 m and could be varied by changing the monomer concentration between 2 and 10% (v/v) and by means of the time of polymerization. By using photoinitiation instead of thermal initiation, it was possible to avoid coagulum and arrive at spherical particles with an exceptionally high monodispersity for particles of this size range (polydispersity index < 1.02) and with monomer loadings well above 5%.
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| 5. |
- Goitom, Daniel, et al.
(författare)
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Noise characteristics and analytical precision of inductively coupled plasma mass spectrometry using a Vulkan direct injection nebuliser for sample introduction
- 2006
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Ingår i: Journal of Analytical Atomic Spectrometry. - London : Royal Society of Chemistry. - 0267-9477 .- 1364-5544. ; 22:2, s. 168-176
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Tidskriftsartikel (refereegranskat)abstract
- Noise and precision of ion count rate measurements were characterised for ICP-MS using a Vulkan direct injection nebuliser (Vulkan DIN) for sample introduction. For comparison, experiments were also carried out using a direct injection high efficiency nebuliser (DIHEN). The Vulkan DIN gave considerably higher relative white noise compared with the DIHEN, −40.3 compared with −45.8 dB, and measurements of aerosol characteristics showed that this was a result of broader size distribution and larger mean size of droplets for the Vulkan DIN. At a liquid flow rate of 85 μL min−1, the aerosol volume fraction constituted by droplets with a diameter smaller than 10 μm was only 5% for the Vulkan DIN compared to 38% for the DIHEN, and the Sauter mean diameter was 30.2 and 11.1 μm, respectively. Compared with the DIHEN, interference noise from a peristaltic pump was very small with the Vulkan DIN because at the liquid flow rate giving maximum sensitivity, the analyte signal intensity was not much affected by changes in liquid flow rate. Although this had a positive effect on precision, it indicated that the plasma is cooled by large droplets that do not positively contribute to the analyte signal intensity. For analytical precision data it was evident that with the Vulkan DIN, precision was limited by the high white noise in the frequency range 0.4–500 Hz, but for the DIHEN there were relatively large contributions from 1/f and/or interference noise to the observed precision. When using integration times of 1000 ms or longer, the DIHEN did, however, appear to give slightly better precision for most of the isotopes tested. For comparison, precision data was also generated when using a conventional spray chamber sample introduction system and it was found that, with a 3000 ms integration time, both direct injection nebulisers gave better precision for most isotopes. Although analytical precision is impressive, the results in this paper also show that both direct injection nebulisers produce aerosols that are far from ideal for the types of ICPs currently used in commercial instruments.
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| 6. |
- Goitom, Daniel, et al.
(författare)
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Radial ICP characteristics for ICP-AES using direct injection or microconcentric nebulisation
- 2005
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Ingår i: Journal of Analytical Atomic Spectrometry. - London : Royal Society of Chemistry. - 0267-9477 .- 1364-5544. ; 20:7, s. 645-651
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Tidskriftsartikel (refereegranskat)abstract
- Radial analyte signal intensities, fundamental plasma parameters, and non-spectral interference effects were characterized for inductively coupled plasma atomic emission spectrometry (ICP-AES) using a direct injection nebuliser (Vulkan DIN) or a microconcentric nebuliser (MCN) coupled to a cyclonic spray chamber for sample introduction. Radial analyte signal intensity profiles for atomic and ionic lines with energy sum (Esum) between 1.85 and 15.41 eV were used. When using the MCN system, for all lines the signal intensity profiles were parabolic with maxima at the axial centre of the plasma. For the Vulkan DIN, the shapes of the profiles were dependent on their Esum showing minimum intensities at the axial centre of the plasma for lines with high Esum values. The ionisation temperature, electron number density and magnesium ion-atom line intensity ratio determined indicated that ionisation and excitation capabilities were deteriorated at the centre of the plasma when using the Vulkan DIN compared with the MCN. This was found to be not simply a result of high aerosol load when using the Vulkan DIN, but because of poor plasma–aerosol interaction, possibly caused by the confined distribution of aerosol in the plasma and high nebuliser gas velocity. Indeed, for the Vulkan DIN, electron number density and ionisation temperature increased with liquid flow rate, which could be explained by plasma shrinkage, or the thermal pinch effect, which increased the aerosol–plasma interaction at increased liquid flow rates. As a consequence, when increasing the liquid flow rate in the range 20–90 µL min–1: (i) analyte sensitivity increased linearly; (ii) the plasma became unstable; (iii) the magnitude of matrix effects remained almost unaffected. These results are partly in contrast to observations made with other types of direct injection nebulisers and ICP instruments.
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| 7. |
- Larsson, Tom, et al.
(författare)
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Species specific isotope dilution with on line derivatisation for determination of gaseous mercury species
- 2005
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Ingår i: Journal of Analytical Atomic Spectrometry. - : RCS Publishing. - 0267-9477 .- 1364-5544. ; 20:11, s. 1232-1239
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Tidskriftsartikel (refereegranskat)abstract
- A species specific isotope dilution (SSID) method for determination of the volatile mercury (Hg) species Hg0, (CH3)2Hg, CH3HgX and HgX2(where X is a counter ion) in gaseous samples was developed. The procedure involved on line derivatisation of ionic Hg species with sodium tetraethylborate during sampling, before collection of species on a Tenax TA tube in series with an Au–Pt tube. Collected species were thermally desorbed and determined by GC-ICP-MS. The procedure provided absolute detection limits of 0.5 pg for CH3HgX and (CH3)2Hg, 5 pg for HgX2 and 25 pg for Hg0. Recoveries and transformations of the investigated species were studied for the different procedural steps and the method was tested for microcosm experiments on brackish water sediment samples, as well as for laboratory air samples. As a result of methylation and reduction processes within the sediment, gaseous emission rates could be determined for all investigated species after addition of an isotope enriched aqueous inorganic 199Hg2+ standard to the sediment. Hg0 was the only specie detected in laboratory air samples (4.5 ng m–3). The procedure for derivatisation of ionic Hg species prior to collection on Tenax TA reduces memory effects and transformations of CH3HgX and HgX2, which is especially advantageous at low sample gas flow rates and for complex gaseous matrices, such as emissions from sediment samples. SSID provides simplified methodological development, as well as efficient correction for matrix induced losses and transformations of Hg species. The method could be useful for various biogeochemical studies of Hg, as well as for reliable risk assessments during, for example, waste management and soil remediation.
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| 8. |
- Mason, P.R.D., et al.
(författare)
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In situ determination of sulfur isotopes in sulfur-rich materials by laser ablation multiple-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS)
- 2006
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Ingår i: JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY. - : Royal Society of Chemistry (RSC). - 0267-9477. ; 21:2, s. 177-186
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Tidskriftsartikel (refereegranskat)abstract
- A new method has been developed for the accurate and precise measurement of sulfur isotopes (S-32, S-33, S-34) in solids on a scale down to 80-100 pin by laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). The method was developed independently on two different sets of instrumentation, both of which give equivalent results with comparable accuracy and precision. The first instrumental set-up utilizes Xe gas in a hexapole collision and reaction cell for interference attenuation coupled with a mass discrimination correction by external normalization using a nebulised vapour of Cl-37/Cl-35 standard solution. The second employs high mass resolution by sector field mass spectrometry to avoid the interfering O2+ isobars with a Si-30/Si-29 standard aerosol for external normalization. The external isotope mass discrimination correction was applied using the exponential law and was further calibrated for both sets of instrumentation by linear interpolation in a sample-standard bracketing method. Mean delta(34)S(V-CDT) and delta(33)S(V-CDT) show excellent agreement (within analytical error, typically 0.6 and 1.5%, respectively) with compiled data for IAEA-S series AgS standard reference materials. Results for NIST SRM 127 (sulfate) were less accurate when calibrated against the IAEA-S series sulfides, whilst significant and consistent deviations in accuracy of up to 3%. were observed in both sets of instrumentation for Soufre de Lacq SRM sulfur. Such generic matrix effects may be widespread in LA-ICP-MS due to differential ablation rates, particle formation, particle transport efficiency and ionization efficiency in an argon plasma.
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| 9. |
- Nguyen Van, Dong, et al.
(författare)
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A comparison between continuum- and line source AAS for speciation analysis of butyl- and phenyltin compounds
- 2006
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Ingår i: Journal of Analytical Atomic Spectrometry. - London : Royal Society of Chemistry. - 0267-9477 .- 1364-5544. ; 21:7, s. 708-711
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Tidskriftsartikel (refereegranskat)abstract
- The analytical potential of using instrumentation based on AAS for speciation analysis was investigated. Organic tin (OT) species were determined following gas chromatographic (GC) separation, atomization in a quartz tube (QT) and detection by line source AAS (LSAAS) and, for comparison, by state of the art continuum source AAS (CSAAS). For an unbiased comparison of the AAS instruments, their working conditions were individually optimized. For CSAAS, the linear range was limited by the GC column capacity (10-1600 ng g-1) and for LSAAS this range was limited by stray radiation (20-1000 ng g-1). With background correction, the instrumental LODs for OT were 6-22 pg as tin for CSAAS, while for LSAAS corresponding values were five to ten times poorer. Without background correction, the LOD of CSAAS was twice as good as that of LSAAS. For method validation, two certified reference materials, Harbour Sediment BCR-646 and Oyster Tissue BCR-710, were analysed.
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| 10. |
- Nguyen Van, Dong, et al.
(författare)
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Redistribution reactions of butyl- and phenyltin species during storage in methanol
- 2005
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 20, s. 266-72
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Tidskriftsartikel (refereegranskat)abstract
- The stability of organotin species, which are frequently used as standards, in methanol has been investigated by gas chromatography coupled to either quartz furnace atomic absorption spectrometry, inductively coupled plasma mass spectrometry or mass spectrometry. Ethylation with sodium tetraethylborate was used during sample preparation. The species composition of single or mixed standard solutions at a concentration of 10 µg g–1 was investigated after storing at –20 °C, +4 °C and +22 °C for various time periods. All butyltin species (monobutyltin—MBT, dibutyltin—DBT and tributyltin—TBT) were found to be stable for all storage conditions, even when mixed. The single triphenyltin (TPhT) standard was also stable, whereas mono-and diphenyltin (MPhT; DPhT) were unstable. MPhT redistributed to DPhT and inorganic tin (IOT), while DPhT redistributed to MPhT and to a minor extent to TPhT. In a mixture containing MBT, DBT, TBT, MPhT, DPhT and TPhT, besides the above mentioned reactions, DPhT was found to react strongly with MBT forming up to 73% monobutyl-monophenyltin (MBMPhT) and MPhT. The composition of MBMPhT was investigated by GC-MS. Suggestions for the type of reactions leading to the redistribution of OT species are outlined and suggestions on how to prepare stable OT standards are made.
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