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5. Species-specific isotope dilution with permeation tubes for determination of gaseous mercury species

Author

Larsson, T. and Frech, W.

Subjects
Mass spectrometry -- Usage, Borates, Solution (Chemistry), Gases, Mercury compounds, Chemical compounds, Chemistry, Analytic -- Research, Chemistry
Abstract

Instrumentation and methodology for determination of the gaseous mercury species [Hg.sup.0], [(C[H.sub.3]).sub.2]Hg, and C[H.sub.3][Hg.sup.+] has been developed. The method is based on continuous addition of gaseous isotopically enriched Hg species (tracers) at the point of sample acquisition, in combination with reduced pressure sampling on Carbotrap adsorbent tubes. Permeation tubes are used for generation of the tracers. Collected species are thermally desorbed and purged through an aqueous sodium tetraethylborate solution for derivatization of C[H.sub.3][Hg.sup.+]. The purged gas is dried with a Nation membrane, and the Hg species are subsequently collected on a smaller Tenax TA adsorbent tube. Species are then thermally desorbed from the Tenax TA and introduced into a gas chromatograph connected to an inductively coupled plasma mass spectrometer for separation and detection. To be able to add tracers during field sampling, we developed a portable device, supplying the permeation tubes with a thermostated and mass flow-controlled air stream of 5.0 [+ or -] 0.1 [degrees]C and 50.0 mL [min.sup.-1], respectively. Typical permeation rates obtained during a period of more than 6 weeks were 12.93 [+ or -] 0.56, 0.42 [+ or -] 0.01, and 0.49 [+ or -] 0.03 (mean [+ or -] standard deviation) pg of Hg [min.sup.-1] for a set of [sup.199][Hg.sup.0], [(C[H.sub.3]).sub.2] [sup.198]Hg, and C[H.sub.3][sup.200][Hg.sup.+] tubes, respectively. Methodological detection limits (3[sigma]) were determined to 700 pg of Hg [m.sup.-3] for [Hg.sup.0] and 50 pg of Hg [m.sup.-3] for [(C[H.sub.3]).sub.2]Hg and C[H.sub.3][Hg.sup.+]. The collection efficiencies for sampled volumes of 400 L of synthetic air on the Carbotrap tubes used in this study were 13 [+ or -] 2, 102 [+ or -] 2, and 99 [+ or -] 4% for [Hg.sup.0], [(C[H.sub.3]).sub.2]Hg, and C[H.sub.3][Hg.sup.+], respectively. Desorption efficiencies for the above species and tubes were 98 [+ or -] 2, 98 [+ or -] 1, and 90 [+ or -] 4%, respectively. Fractions (20-40%) of the added [(C[H.sub.3]).sub.2] [sup.198]Hg and C[H.sub.3][sup.200][Hg.sup.+] tracers were found to be transformed during the analytical processing of collected air samples. Determined concentrations in the research laboratory air, corrected for species transformations, were 3-53, 8-11, and 1-2 ng of Hg [min.sup.-3] for [Hg.sup.0], [(C[H.sub.3]).sub.2]Hg, and C[H.sub.3][Hg.sup.+], respectively. Concentrations in the ambient air were determined to be 2.1-2.6 ng [m.sup.-3] for [Hg.sup.0] and below the detection limit for [(C[H.sub.3]).sub.2]Hg and C[H.sub.3][Hg.sup.+].

Published
2003

17. Spatiotemporal visualization of the dynamics of absorbing layers in a two-stage atomizer

Author

Nagulin K., Gil'mutdinov A., Axner O., and Frech W.

Subjects
Condensed Matter::Quantum Gases, Physics::Optics, Physics::Atomic Physics
Abstract

This paper describes an experimental apparatus for studying the dynamics of the variation of the spatial distribution of the absorbing layers in a two-stage atomizer. An optical system with a telecentric beam, using a diode laser as the radiation source, is proposed and analyzed. The spatiotemporal resolution and the contribution of refraction effects to the resulting absorption pattern are estimated. The dynamics of the evaporation and condensation processes are visualized in a two-stage atomizer of Cd atoms and NaCl molecules.

Published
2002

18. Microstructure and mechanical properties of rapidly solidified Fe-25%Cr-5%Al ribbons produced by planar flow casting

Author

Jiménez, José Antonio, Frech, W., Ruano, Oscar Antonio, and Frommeyer, G.

Subjects
Metallographic microstructure, Mechanical properties, Grain size and shape, Rapid solidification
Abstract

Catalyst substrate foils of the highly oxidation resistant Fe-25Cr-5Al alloy (mass contents in%) with a thickness ranging from 40 to 180 μm have been produced by planar flow casting. The rapidly solidified ribbons showed a monophase ferritic microstructure of columnar grains. The grain size determined over a section parallel to the ribbon wheel side ranged from 5 μm for the thin ribbons (40 μm) to 18 μm for the thicker ones (180 μm). This anisotropic columnar solidification microstructure exhibits a strong 〈100〉 fiber texture, with the fiber axis nearly perpendicular to the plane of the ribbon. The position of the maximum in the pole figure was tilted from the center point toward the casting direction. Results of uniaxial tensile tests showed that only the yield stress data of the ribbons in the as-cast condition are reproducible, whereas the ultimate tensile strength and the elongation to failure data show a wide scatter band. The fracture mode exhibits ductile features such as glide bands and dimples.

Published
1995

19. Mercury species transformations during sample pre-treatment of biological tissues studied by HPLC-ICP-MS

Author

Qvarnström, Johanna, Frech, W., Qvarnström, Johanna, and Frech, W.

Abstract

A high-performance liquid chromatography (HPLC) system with a C18 column and an aqueous phase eluent (0.08% ammonium acetate and 0.02% L-cysteine) was directly connected to an inductively coupled plasma mass spectrometer (ICP-MS). HPLC-ICP-MS was used to study the abiotic formation of methylmercury, CH3Hg+, from inorganic mercury, Hg2+, as well as demethylation of CH3Hg+ to Hg2+ in biological tissues during treatment with tetramethylammonium hydroxide (TMAH) followed by pH adjustment with citric or acetic acid. Enriched isotope standards from CH3198Hg+ and 201Hg2+ were added to the samples to monitor species transformation and to apply species-specific isotope dilution (SSID) calibration. Depending on the type of sample matrix, up to 11.5% of added Hg2+ was methylated and up to 6.26% CH3Hg+ was demethylated to Hg2+. Methylation of Hg2+ probably takes place mainly during and after pH adjustment and it decreases after prolonged TMAH treatment. To minimize abiotic methylation, it is therefore recommended to proceed with pH adjustment after samples have been treated with TMAH for 24 h. There is no significant difference in the degree of methylation using citric or acetic acid.

Published
2002
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23. Towards a new Certified Reference Material for butyltins, methylmercury and arsenobetaine in oyster tissue

Author

Morabito, R., primary, Massanisso, P., additional, Cámara, C., additional, Larsson, T., additional, Frech, W., additional, Kramer, K.J.M., additional, Bianchi, M., additional, Muntau, H., additional, Donard, O.F.X., additional, Lobinski, R., additional, McSheehy, S., additional, Pannier, F., additional, Potin-Gautier, M., additional, Gawlik, B.M., additional, Bøwadt, S., additional, and Quevauviller, Ph., additional

Published
2004
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41. Applications of enriched stable isotope tracers in combination with isotope dilution GC-ICP-MS to study mercury species transformation in sea sediments during in situ ethylation and determination

Author

Lambertsson, L., Lundberg, E., Nilsson, M., and Frech, W.

Abstract

An isotope dilution (ID) based GC-ICP-MS method, able to simultaneously determine incipient concentrations of methylmercury as well as the degree of methylation of inorganic mercury and de-methylation of methylmercury in brackish water sediments, was developed. Methyl- and inorganic mercury were extracted from the sediments using a solution containing KBr–H2SO4–CuSO4. CH3200Hg+ was added as a species-specific internal standard and 199Hg2+ to monitor artefact formation of methylmercury during sample work-up. Extracted mercury species were treated with NaBEt4 to form ethyl derivatives that were trapped on Tenax. The typical precision of the method was in the range of 2–3% RSD for methylmercury concentrations of 2–5 ng g−1 sediment (dry weight). The detection limit of the method based on 3 times the standard deviation of repeated sediment analysis was 0.3 ng g−1 sediment as the metal. When using bromide for extraction, degradation of methylmercury into elemental mercury and the probable formation of methylmercury bromide during sample pretreatment and/or analysis were observed. For investigations of mercury methylation and de-methylation during sample incubation, 201Hg2+ and CH3198Hg+ were added to sediment layers at 20% of the ambient concentrations of the two species. Mercury methylation and de-methylation activities differed by a factor of four between depths and were highest in the top 3 cm of the sediment. In this region 9.5% of the added 201Hg2+ tracer was methylated and 79% of the CH3198Hg+ tracer was de-methylated. Detection limits for methylation of 201Hg2+ and de-methylation of CH3198Hg+ were 0.1 ng g−1 and 0.2 ng g−1, respectively. Methylmercury concentrations changed about 5 times over the depth profile, which implies that samples have to be taken over a well-defined depth when assessing representative data.

Published
2001

44. Analysis of solid samples by graphite furnace atomic emission spectrometry

Author

Baxter, D. and Frech, W.

Abstract

Summary: The possibility of determining a range of analytes in solid samples using a single set of optimised ‘multi-element’ instrumental parameters for a graphite furnace atomic emission spectrometry (GFAES) system was investigated. Accurate results for silver, manganese, nickel, lead and vanadium in solid reference materials of biological origin were obtained using peak area evaluation and calibration against standard solution curves. The versatility of the constant-temperature atomiser enabled lead and silver in metallurgical samples to be determined as well, although quantification against standard steel materials was necessary in the case of silver to obtain acceptable results.

Published
1987
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