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Quetel C.R.,European Commission | Vassileva E.,European Commission | Vassileva E.,IAEA Marine Environment Laboratories | Petrov I.,European Commission | And 2 more authors.
Analytical and Bioanalytical Chemistry | Year: 2010

This paper describes the application of TiO2 nano-particles (anatase form) for the solid-phase extraction of iron from coastal seawater samples. We investigated the adsorption processes by infra-red spectroscopy. We compared in batch and on-(mini)column extraction approaches (0.1 and 0.05 g TiO2 per sample, respectively), combined to external calibration and detection by inductively coupled plasma mass spectrometry at medium mass resolution. Globally, this titania phase was slightly more efficient with seawater than with ultra-pure water, although between pH 2 and pH 7, the Fe retention efficiency progressed more in ultra-pure water than in seawater (6.9 versus 4.8 times improvement). Different reaction schemes are proposed between Fe(III) species and the two main categories of titania sites at pH 2 (adsorption of [FeL x ](3-x)+ via possibly the mediation of chlorides) and at pH 7 (adsorption of [Fe(OH)2]+ and precipitation of [Fe(OH)3]0). Under optimised conditions, the inlet system was pre-cleaned by pumping 6% HCl for ∼2 h, and the column was conditioned by aspirating ultra-pure water (1.7 g min-1) and 0.05% ammonia (0.6 g min-1) for 1 min. Then 3 g seawater sample was loaded at the same flow rate while being mixed on-line with 0.05% ammonia at 0.6 g min-1 to adjust the pH to 7. The iron retained on the oxide powder was then eluted with 3 g 6% HCl (<0.002% residual salinity in the separated samples). The overall procedural blank was 220 ± 46 (2 s, n = 16) ng Fe kg-1 (the titania was renewed in the column every 20 samples, with 2-min rinsing in between samples with 6% HCl at 1.5 g min-1). The recovery estimated from the Canadian certified reference material CASS-2 was 69.5 ± 7.6% (2 s, n = 4). Typically, the relative combined uncertainty (k = 2) estimated for the measurement of ∼1 μg Fe kg-1 (0.45 μm filtered and acidified to pH 1.5) of seawater was ∼12%. We applied our method to a similar sample, from the coastal region of the North Sea. The agreement well within stated uncertainties of our result with the value obtained independently by isotope dilution mass spectrometry further validated our method. © 2010 Springer-Verlag. Source

Garcia-Ruiz S.,European Commission | Petrov I.,European Commission | Petrov I.,Free University of Colombia | Vassileva E.,European Commission | And 2 more authors.
Analytical and Bioanalytical Chemistry | Year: 2011

The cadmium content in surface water is regulated by the last European Water Framework Directive to a maximum between 0.08 and 0.25 μg L -1 depending on the water type and hardness. Direct measurement of cadmium at this low level is not straightforward in real samples, and we hereby propose a validated method capable of addressing cadmium content below μg L-1 level in natural water. It is based on solid-phase extraction using TiO2 nanoparticles as solid sorbent (0.05 g packed in mini-columns) to allow the separation and preconcentration of cadmium from the sample, combined to direct isotope dilution and detection by inductively coupled plasma mass spectrometry (ID-ICP-MS). The extraction setup is miniaturised and semi-automated to reduce risks of sample contamination and improve reproducibility. Procedural blanks for the whole measurement process were 5.3 ± 2.8 ng kg-1 (1 s) for 50 g of ultrapure water preconcentrated ten times. Experimental conditions influencing the separation (including loading pH, sample flow rates, and acid concentration in the eluent) were evaluated. With isotope dilution the Cd recovery rate does not have to be evaluated carefully. Moreover, the mathematical model associated to IDMS is known, and provides transparency for the uncertainty propagation. Our validation protocol was in agreement with guidelines of the ISO/IEC 17025 standard (chapter 5.4.5). Firstly, we assessed the experimental factors influencing the final result. Secondly, we compared the isotope ratios measured after our separation procedure to the reference values obtained with a different protocol for the digested test material IMEP-111 (mineral feed). Thirdly, we analysed the certified reference material BCR-609 (groundwater). Finally, combined uncertainties associated to our results were estimated according to ISO-GUM guidelines (typically, 3-4% k = 2 for a cadmium content of around 100 ng kg -1). We applied the developed method to the groundwater and wastewater samples ERM-CA615 and BCR-713, respectively, and results agreed with certificate values within uncertainty statements. [Figure not available: see fulltext.] © 2011 Springer-Verlag. Source

Vassileva E.,IAEA Marine Environment Laboratories | Hoenig M.,Research Center
Analytica Chimica Acta | Year: 2011

This paper describes the determination of the total and extractable mass fractions of Cd and Pb in mineral feed test sample distributed by the Community Reference Laboratory for Heavy Metals in Feed and Food (CRL-HM), in the frame of the fifth interlaboratory comparison for the European Union National Reference Laboratories (NRL).The developed in this study protocol for the total and extractable mass fractions of Pb and Cd in mineral feed sample is based on isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS). The applied dual spiking approach reduced by 50% the number of analytical steps. The addition of hydrofluoric acid in the digestion step was found necessary to ensure a full decomposition and complete isotope equilibration. Quadrupole inductively coupled plasma mass spectrometer equipped with collision reaction interface (CRI) was employed for the measurements of Cd and Pb. Two methods for the determination of Cd were applied and compared. In the first one the high molybdenum content was reduced by introduction of matrix separation step followed by standard ICP-MS mode measurement, whereas in the second one CRI mode was used for the determination of Cd without preliminary matrix separation. The estimation of the combined uncertainty was performed according to the ISO guidelines. Uncertainty propagation was used as a tool for validation of proposed analytical procedure. Contributions from the correction for moisture content, sample homogeneity, procedural blank, instrumental background and dead time effects were evaluated in both cases. The largest uncertainty contributors for Cd and Pb is due to the within bottle homogeneity of the mineral feed sample - 50.3% and 90% respectively. The IUPAC data for isotope composition are the second major contributor to the combined uncertainty of the result for the total mass fraction of Cd in mineral feed - 43.3%. However, the ID ICP-MS results achieved from the two series of samples (partial and total extraction) were in excellent agreement within uncertainty, irrespective of the method used for extraction. The ID ICP-MS results for the total and extractable mass fractions of Cd and Pb in feed sample were compared with the results obtained with external calibration approach and routinely applied in the daily analytical practice of the Belgium National Reference Laboratory for trace elements in food and feed. © 2011 Elsevier B.V. Source

Reinardy H.C.,University of Plymouth | Teyssie J.-L.,IAEA Marine Environment Laboratories | Jeffree R.A.,IAEA Marine Environment Laboratories | Jeffree R.A.,University of Technology, Sydney | And 4 more authors.
Science of the Total Environment | Year: 2011

Understanding uptake and depuration of radionuclides in organisms is necessary to relate exposure to radiation dose and ultimately to biological effects. We investigated uptake and depuration of a mixture of radionuclides to link bioaccumulation with radiation dose in zebrafish, Danio rerio. Adult zebrafish were exposed to radionuclides ( 54Mn, 60Co, 65Zn, 75Se, 109Cd, 110mAg, 134Cs and 241Am) at tracer levels (<200Bqg -1) for 14d, either via water or diet. Radioactivity concentrations were measured in whole body and excised gonads of exposed fish during uptake (14d) and depuration phases (47d and 42d for aqueous and dietary exposures respectively), and dose rates were modelled from activity concentrations in whole body and exposure medium (water or diet). After 14-day aqueous exposure, radionuclides were detected in decreasing activity concentrations: 75Se> 65Zn> 109Cd> 110mAg> 54Mn> 60Co> 241Am> 134Cs (range: 175-8Bqg 1). After dietary exposure the order of radionuclide activity concentration in tissues (Bqg -1) was: 65Zn> 60Co> 75Se> 109Cd> 110mAg> 241Am> 54Mn> 134Cs (range: 91-1Bqg -1). Aqueous exposure resulted in higher whole body activity concentrations for all radionuclides except 60Co. Route of exposure did not appear to influence activity concentrations in gonads, except for 54Mn, 65Zn, and 75Se, which had higher activity concentrations in gonads following aqueous exposure. Highest gonad activity concentrations (Bqg -1) were for 75Se (211), 109Cd (142), and 65Zn (117), and highest dose rates (-Gyh -1) were from 241Am (aqueous, 1050; diet 242). This study links radionuclide bioaccumulation data obtained in laboratory experiments with radiation dose determined by application of a dosimetry modelling tool, an approach that will enable better linkages to be made between exposure, dose, and effects of radionuclides in organisms. © 2011 Elsevier B.V. Source

Martn J.,IAEA Marine Environment Laboratories | Miquel J.-C.,IAEA Marine Environment Laboratories
Geophysical Research Letters | Year: 2010

The northwestern Mediterranean is known to be a privileged area of deep water formation via dense shelf water cascading and offshore convection. The impact of the former in the sedimentary dynamics of the deep basin has been highlighted in recent years, while open sea convection has been solely studied from a hydrological perspective. Particle fluxes and hydrodynamics were monitored at the DYFAMED site (Ligurian Sea, western Mediterranean) at 200, 1000 m and near the seafloor (2350 m depth) during winter 2005-2006. From February to April 2006, and in coincidence with an unusual episode of deep water formation, a notable intensification of currents was observed in the entire water column and near-bottom particle flux increased up to two orders of magnitude. These observations suggest that offshore convection must be taken into account together with cascading as a major driving force for sedimentary dynamics in the deep western Mediterranean. © 2010 by the American Geophysical Union. Source

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