Spectrométrie de masse à plasma à couplage inductif

vignette|alt=photo d'un spectromètre|Un spectromètre Varian pour ICP-MS La spectrométrie de masse à plasma à couplage inductif, ou ICP-MS (), est un type de spectrométrie de masse capable de détecter les métaux et plusieurs non-métaux à des concentrations très faibles, pouvant aller jusqu'à une partie par billiard (\frac{1}{10^{15}}) lorsque le bruit de fond isotopique est assez faible ou interfère peu. Cette analyse est effectuée en ionisant l'échantillon au moyen d'une torche à plasma, puis en analysant le plasma résultant par spectrométrie de masse pour séparer et quantifier ces ions. Comparée à la spectrométrie d'absorption atomique, l'ICP-MS est plus rapide, plus précise et plus sensible. Néanmoins, elle est plus susceptible que d'autres spectrométries de masse (TIMS ou GD-MS) d'introduire des sources d'interférences à l'analyse : argon du plasma, gaz de l'air qui peuvent fuir à travers les orifices coniques, et contaminations par la verrerie ou les cônes. En raiso

Time-resolved size and element analysis of gas-borne nanoparticles

Adrian Hess

Physical and chemical characterization of gas-borne particles in the nanometer to sub-micrometer size range is important in many applications, such as nanoparticle related health studies, the monitoring of powder or dust distribution processes, assessing the release of engineered nanoparticles (ENP) from ENP reinforced materials due to abrasion or combustion, or exposure studies related to ENP containing spray products. Such investigations are also highly valuable in the development of technical processes, e.g. to determine distinct size fractions containing specific elements or isotopes in terms of dealing with nuclear waste, or to evaluate particulate matter in process gases and emissions from thermal waste treatment, gas turbines, or other combustion engines. Such particle speciation includes knowledge about particle size distribution and chemical composition, and if possible obtained with a high time resolution. However, most of the available techniques are offline methods and/or not able to provide such physical and chemical information simultaneously. The Scanning Mobility Particle Sizer (SMPS) is a well-established and widely used equipment for determining size distribution and number concentration of such particles, within scan durations of a few minutes. Inductively Coupled Plasma Mass Spectrometry (ICPMS) is a highly sensitive multi-element technique, which allows determining the elemental composition of normally liquid samples, with excellent detection limits and a wide dynamic concentration range. In this work, SMPS and ICPMS are coupled to one hyphenated system. A Rotating Disk Diluter (RDD) allows directing a well-defined flow of a diluted aerosol into subsequent measuring equipment, which besides is mainly argon based, due to the dilution effect. Therefore an RDD is implemented as sample introduction interface, and the SMPS flow concept is re-designed to fulfil the requirements of both different analytical methods. This coupling strategy allows achieving simultaneous information on particle size and elemental composition, with SMPS-typical time resolutions of a few minutes, and offers high flexibility in terms of dealing with different aerosols, loaded with particles in the nanometer to sub-micrometer size range. Proper SMPS operation under argon atmosphere instead of air is validated. The developed setup is tested with a model aerosol containing air-borne silver nanoparticles. The capabilities are then demonstrated on uniformly composited metal aerosols, as well as an aerosol mixture containing smaller gold and larger silver nanoparticles. Sensitivity and limit of detection, related to particle number and mass concentration, are determined for several elements and particle diameters. After the successful characterization, the instrumentation is applied in two research applications. The first is a study on aerosol particles, released by commercial consumer spray products. In the second application, particulate metal emissions from the thermal treatment of differently impregnated wood samples are investigated, with the focus on alkali metals.

EPFL2016

Scale-up of phosphate remobilization from sewage sludge in a microbial fuel cell

Christos Comninellis, Thomas Egli, Fabian Fischer, Alain-François Grogg, Marc Sugnaux, Géraldine Zufferey

Phosphate remobilization from digested sewage sludge containing iron phosphate was scaled-up in a microbial fuel cell (MFC). A 3 litre triple chambered MFC was constructed. This reactor was operated as a microbial fuel cell and later as a microbial electrolysis cell to accelerate cathodic phosphate remobilization. Applying an additional voltage and exceeding native MFC power accelerated chemical base formation and the related phosphate remobilization rate. The electrolysis approach was extended using a platinum-RVC cathode. The pH rose to 12.6 and phosphate was recovered by 67% in 26 h. This was significantly faster than using microbial fuel cell conditions. Shrinking core modelling particle fluid kinetics showed that the reaction resistance has to move inside the sewage sludge particle for considerable rate enhancement. Remobilized phosphate was subsequently precipitated as struvite and inductively coupled plasma mass spectrometry indicated low levels of cadmium, lead, and other metals as required by law for recycling fertilizers. (C) 2015 Elsevier Ltd. All rights reserved.

Elsevier Sci Ltd2016

Influence of power switching on power line communications in medium voltage networks

Emmanuel Marthe

A complete framework dealing with power line communication in medium voltage network is proposed. Based on path loss measurements, a complete characterisation of inductive couplers is performed. After a brief recall of inductive coupling techniques, we address the issue of power switching influence on inductive coupler performances. Finally, we show the key role of the medium voltage to low voltage transformer for a phase to ground propagation mode

2004

Time-resolved size and element analysis of gas-borne nanoparticles

Adrian Hess

EPFL2016