Grethe Wibetoe

Springtime depletion of mercury in the European Arctic as observed at Svalbard.

This study was carried out to see whether the geographical extent of the mercury depletion events (MDEs), first seen at Alert in the Canadian High Arctic, is also covering Svalbard. Another goal was to determine the main reaction products from the MDE and their fate. Gaseous elemental mercury (GEM), total particulate mercury (TPM), reactive gaseous mercury (RGM) and total mercury in surface snow have been measured at the Zeppelin mountain during 2000. GEM has been measured with a high time resolution automatic monitor (Tekran 2537A) based on CV-AFS, TPM was sampled/measured using high volume samplers/CV-AFS and RGM was sampled with annular denuders and measured by CV-AFS (Gardis Hg-monitor). During spring of 2000, in the three-month period following polar sunrise, there were several episodic depletions in GEM concentration correlating well with the depletion of surface ozone. Measurements of RGM and TPM showed higher concentrations of these mercury species during the depletion period than during the rest of the year. Total mercury in surface snow showed a distinct increase from the polar night to the Arctic spring. MDEs are caused by the specific chemical and physical conditions observed in the Arctic during spring. GEM is oxidised and converted to more reactive forms (RGM and/or TPM), which have considerably higher deposition velocities than elemental mercury, leading to an overall enhanced deposition flux of mercury.

Speciation analysis of As, Sb and Se in leachates of cementitious construction materials using selective solid phase extraction and ICP-MS

A solid phase extraction (SPE) method has been developed for the separation of As(III), Sb(III) and Se(IV) from As(V), Sb(V) and Se(VI) in leachates of cementitious construction materials. The leachates were treated with ammonium pyrrolidine dithiocarbamate (APDC) and the APDC complexes of As(III), Sb(III) and Se(IV) were retained on a non-polar (C-18) sorbent, whereas As(V), Sb(V) and Se(VI) passed through. The SPE method was optimized in a multivariate approach: the effect of sample pH, APDC concentration, mixing time and sample percolation rate on the extraction of the analyte species was studied, and the optimum conditions of the significant parameters, i.e. sample pH and APDC concentration, were identified and experimentally verified. The two oxidation states of the elements can be separated using the SPE method from solutions of pH 3–8 (As), pH 4–10 (Sb) and pH 3–9 (Se) treated with 0.08% (w/v) APDC. The effect of matrix interferences was studied and the use of benzene sulfonate to remove interfering matrix metal ions by ion-pair SPE was demonstrated. The limit of detection of As(V), Sb(V) and Se(VI) by ICP-MS was 0.09, 0.14 and 0.37 µg L−1, respectively. A condition was established for the preconcentration of As(III), Sb(III) and Se(IV) by elution with 3.0 M HNO3 in a back-flushing mode. With a preconcentration factor of 50, concentrations of As(III), Sb(III) and Se(IV) down to 1–6 ng L−1 could be detected using the SPE method in combination with ICP-MS. The SPE method was validated using spike recovery tests, and was used to determine the oxidation states of the target elements in leachates of a concrete material. As(V), Sb(V) and Se(VI) were found to be the major species in most of the leachates.

Dual mode sample introduction for multi-element determination by ICP-MS: the optimization and use of a method based on simultaneous introduction of vapor formed by NaBH4 reaction and aerosol from the nebulizer

A method has been developed utilizing dual mode sample introduction of a commercial Multi Mode Sample Introduction System (MSIS™) for simultaneous multi-element (As, Bi, Cd, Co, Cu, Ni, Pb, Sb, Zn) determination by ICP-MS. Vapor formed by NaBH4 reaction and aerosol from the nebulizer were introduced simultaneously into the plasma. The effects of parameters that are expected to affect hydride generation of As, Bi and Sb, i.e. concentrations of HNO3, NaBH4 and thiourea, plus flow rates of sample and NaBH4, were evaluated using Plankett–Burman experimental design. Then, the most significant of the parameters were optimized using a central composite design. Further, as optimum values were not the same for all the elements, a response optimizer was used to obtain a compromised optimum. Except for Pb, the sensitivity of the ‘classical’ hydride generating elements (As, Bi and Sb) increased significantly using the dual mode sample introduction, compared to pneumatic nebulization. The factors of sensitivity increase for As, Bi and Sb were 77, 33 and 56, respectively. For the other elements (Cd, Co, Cu, Ni and Zn), that are also reported to react with NaBH4 forming volatile species, no significant change in sensitivity was observed. The limits of detection obtained for As, Bi, and Sb using dual mode sample introduction were 7, 15 and 10 pg mL−1, respectively. The use of thiourea as a pre-reducing agent and masking agent was also investigated. The accuracy of the method was verified by analyzing various certified reference materials (CRMs): SRM1572 ‘Citrus leaves’, SRM1575 ‘Pine Needles’, SRM1643e ‘Trace Elements in Water’, GBW07602 ‘Bush Branches and Leaves’ and GBW07601 ‘Human hair’.

Spectral interferences and background overcompensation in zeeman-corrected atomic absorption spectrometry : Part 1. The effect of iron on 30 elements and 49 element lines

Abstract The background compensation performance of a Zeeman corrector with the magnetic field acting on the graphite atomization cell was assessed for 30 elements and 49 element lines in an iron matrix. Two of the elements studied, gallium and zinc, are influenced by background overcompensation which introduces serious negative systematic errors. The overcompensation is due to the presence of iron lines close to the 287.4-nm gallium line and the 213.9-nm zinc line; when the magnetic field is on, the σ-components of the adjacent iron lines overlap at the position of the analyte line and a background, which is not present when the magnetic field is off, is recorded. When gallium and zinc are measured under the same conditions but with deuterium arc background correction, the adjacent iron lines cause positive systematic errors. These spectral interferences for gallium in the presence of iron can be avoided by doing the measurements at the 294.4-nm gallium line; the two lines have about the same sensitivity. When zinc is to be measured at the 213.9-nm line, with either type of background correction, the spectral interferences from iron can be avoided by careful selection of the graphite-furnace parameters. In addition to spectral interferences, iron also affects the sensitivity for both gallium and zinc.

Field site leaching from recycled concrete aggregates applied as sub-base material in road construction

The release of major and trace elements from recycled concrete aggregates used in an asphalt covered road sub-base has been monitored for more than 4 years. A similar test field without an asphalt cover, directly exposed to air and rain, and an asphalt covered reference field with natural aggregates in the sub-base were also included in the study. It was found that the pH of the infiltration water from the road sub-base with asphalt covered concrete aggregates decreased from 12.6 to below pH 10 after 2.5 years of exposure, whereas this pH was reached within only one year for the uncovered field. Vertical temperature profiles established for the sub-base, could explain the measured infiltration during parts of the winter season. When the release of major and trace elements as function of field pH was compared with pH dependent release data measured in the laboratory, some similar pH trends were found. The field concentrations of Cd, Ni, Pb and Zn were found to be low throughout the monitoring period. During two of the winter seasons, a concentration increase of Cr and Mo was observed, possibly due to the use of de-icing salt. The concentrations of the trace constituents did not exceed Norwegian acceptance criteria for ground water and surface water Class II.

Determination of cobalt, nickel and copper in flowers, leaves, stem and roots of plants using ultrasonic slurry sampling electrothermal atomic absorption spectrometry

An ultrasonic slurry sampling electrothermal atomic absorption spectrometric method was developed and used for the determination of Co, Ni and Cu in the four plant species Helichrysum candolleanum , Peristrophe decorticans , Blepharis diverspinia and Tephrosia burchelli . The plants were sampled in a copper–nickel mining site in Botswana, Africa. For each plant species, flowers, leaves, stem and roots were analysed. The concentration range of the elements was 0.2–10 µg g -1 for Co, 20–400 µg g -1 for Ni and 30–600 µg g -1 for Cu. The method was validated by comparing the results from slurry sampling with those from the analysis of decomposed samples. The two methods gave comparable precision and accuracy. The relative standard deviations were in the range 1–14 and 1–20% for slurry sampling and decomposed materials, respectively. Analysis of certified plant reference materials also confirmed the accuracy of the method; no significant difference from the certified values was found when the slurry sampling technique was used.

Spectral interferences and background overcompensation in inverse zeeman-corrected atomic absorption spectrometry Part 3. Study of eighteen cases of spectral interference

Abstract Atomic line tables were surveyed in order to select pairs of elements which have contiguous lines and so are likely to suffer from spectral interference. Spectrometric measurements of these element pairs revealed eighteen cases of spectral interference. Four of these cases occurred at the recommended wavelengths for the analyte: the 459.4-nm europium line (interference form vanadium and cesium), the 247.6-nm palladium line (interference from lead) and the 265.9-nm platinum line (interference from europium).

Spectral interferences and background overcompensation in inverse zeeman-corrected atomic absorption spectrometry : Part 2. The effects of cobalt, manganese and nickel on 30 elements and 53 elements lines

Abstract The background compensation performance of a transversal alternating-current Zeeman corrector system with the magnet acting on the graphite atomization cell was assessed for 30 elements and 53 element lines in the presence of relatively large amounts of cobalt, manganese or nicke. The study reveaaled three cases of background overcompensation, all being caused by a cobalt line adjacent to the analytical line. When the magnetic field is on (and the background is measured), a σ-component of the cobalt lines overlaps the emission lines of boron (249.7 nm), mercury (253.7nm) and gold (267.6 nm). The interfering effect on boron is small, but mercury and gold are more seriously affected; for both elements a serious negative systematic error is introduced. Manganese and nickel did not give any overcompensation effects on the elements and lines studied. When gold and mercury were measured with the use of the same experimental parameters and a conventional deuterium-arc background corrector, only mercury suffered from spectral interference. The spectral interference of cobalt on mercury, with either type of background correction, can be avoided by selecting a proper furnace program. When gold is tobe measured in the presence of cobalt and with the present Zeeman background-correction system, the 267.6.-nm line should not be used; the more sensitive 242.8 nm line is recommended.

Determination of endogenous concentrations of the lanthanides in body fluids and tissues using electrothermal vaporization inductively coupled plasma mass spectrometry

A method was developed for the determination of endogenous concentrations of the lanthanides in body fluids and tissues with electrothermal vaporization inductively coupled plasma mass spectrometry. The method was applied to the analysis of rat liver and human blood plasma as well as to some reference materials,viz., Oyster Tissue, Bovine Liver, Seronorm Trace Element Serum and Human Hair. Microwave digestion in high-pressure containers was used to digest the various biological materials. Analyses of undigested biological tissues by slurry sampling and body fluids by direct injection were also performed. For undigested samples, hydrogen peroxide injected directly onto the sample inside the graphite furnace was found to be effective in preventing the build-up of ash in the furnace. Trifluoromethane (Freon-23) was used as an effective chemical modifier that lowered the vaporization temperature and the memory effect significantly for most of the lanthanides. The absolute detection limits were, with few exceptions, in the range 1–20 fg for all the lanthanides in the various biological materials. The relative detection limits varied with the level of dilution and the method used. For Seronorm Trace Element Serum, the relative detection limits were in the range 0.05–1.2 ng l–1. The analytical results for slurry and digested samples of the same material were similar with respect to accuracy and precision. The intermediate precision, i.e., the overall relative standard deviation obtained for the CRMs analysed on three different (not consecutive) days, was less than 25% for the lanthanides with concentrations higher than 1 ng g–1 dry material. In the few cases where a certified or indicative value existed for the concentrations of the lanthanides in the reference materials, good agreement between these concentrations and the concentrations obtained in the present work was found. Blood plasma samples from 30 healthy volunteers and liver samples from ten unexposed rats were analysed. All the lanthanides were above the detection limit in the various samples analysed.

Interferences in inverse zeeman-corrected atomic absorption spectrometry caused by zeeman splitting of molecules

Abstract Orthophosphoric acid was vaporized in the graphite furnace of an inverse Zeeman-corrected atomic absorption spectrometer and the performance of the background corrector system was studied at some analyte lines in the wavelength region where the species PO is known to have strong band systems. The investigation revealed cases of both over- and under-compensation probably caused by Zeeman splitting of PO rotational lines.