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Dübendorf, Switzerland

Gemayel R.,Aix - Marseille University | Hellebust S.,Aix - Marseille University | Temime-Roussel B.,Aix - Marseille University | Hayeck N.,Aix - Marseille University | And 5 more authors.
Atmospheric Measurement Techniques | Year: 2016

Hyphenated laser ablation-mass spectrometry instruments have been recognized as useful analytical tools for the detection and chemical characterization of aerosol particles. Here we describe the performances of a laser ablation aerosol particle time-of-flight mass spectrometer (LAAP-ToF-MS) which was designed for aerodynamic particle sizing using two 405 nm scattering lasers and characterization of the chemical composition of single aerosol particle via ablation/ionization by a 193 nm excimer laser and detection in a bipolar time-of-flight mass spectrometer with a mass resolving power of m/Δm > 600. We describe a laboratory based optimization strategy for the development of an analytical methodology for characterization of atmospheric particles using the LAAP-ToF-MS instrument in combination with a particle generator, a differential mobility analyzer and an optical particle counter. We investigated the influence of particle number concentration, particle size and particle composition on the detection efficiency. The detection efficiency is a product of the scattering efficiency of the laser diodes and the ionization efficiency or hit rate of the excimer laser. The scattering efficiency was found to vary between 0.6 and 1.9% with an average of 1.1%; the relative standard deviation (RSD) was 17.0%. The hit rate exhibited good repeatability with an average value of 63% and an RSD of 18%. In addition to laboratory tests, the LAAP-ToF-MS was used to sample ambient air during a period of 6 days at the campus of Aix-Marseille University, situated in the city center of Marseille, France. The optimized LAAP-ToF-MS methodology enables high temporal resolution measurements of the chemical composition of ambient particles, provides new insights into environmental science, and a new investigative tool for atmospheric chemistry and physics, aerosol science and health impact studies. © Author(s) 2016. Source


Van Houcke S.K.,Ghent University | Thienpont L.M.,Laboratory for Analytical Chemistry
Clinical Chemistry and Laboratory Medicine | Year: 2013

Clinical samples are the cornerstone in all aspects related to in vitro diagnostic testing. They are particularly valuable in the process of establishing/validating metrological traceability, because they eliminate commutability issues potentially associated with artificial calibrators. Therefore, they are essential for IFCC standardization projects. However, sourcing clinical specimens is particularly challenging. It mostly turns out that only dedicated supply sources can accommodate the varying specifications within reasonable timelines. Here we describe the torturous experience in this regard of the IFCC Working Group for Standardization of Thyroid Function tests (since transformed into a Committee). We always focused on obtaining high quality samples in sufficient volume to serve all project participants. We applied a step-up approach: in phase I, we used high volume (200 mL of plasma/serum) single donations from apparently healthy individuals, and switched in phase II and III to medium-sized volume clinical samples (15 - 30 mL) from well-defined patient categories. In the first two phases we observed for some assays a sample-related discrepant analytical performance for total/free triiodothyronine and thyroid stimulating hormone (TSH), whereas in phase III we faced a severe delay in obtaining the relevant panels for free thyroxine (FT4) and TSH (n = 90 and n = 100, respectively). Additional experiments only allowed us to exclude hypothesized causes of the observations. We believe that there would be merit in a collaborative effort by chairholders of similar projects to establish a sample procurement infrastructure based on a solid relationship with commercial supply sources with the support of a significant number of committed clinicians. Source


Losert S.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Losert S.,Laboratory for Analytical Chemistry | Losert S.,ETH Zurich | Hungerbuhler K.,ETH Zurich | And 2 more authors.
Technical Proceedings of the 2013 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2013 | Year: 2013

Nanoparticle containing sprays are categorized as critical consumer products due to their direct exposure path via lungs. Recent studies proposed first analytical concepts for simulated exposure experiments and proper risk assessment. Nevertheless these studies lack from systematic evaluation. This work aims on providing necessary knowledge for identification of the most critical nanoparticle types and consumer spray application. The goal is to provide optimization and validation of analytical concepts for proper quantification and a proportion of guidelines for appropriate analytical simulation experiments. Source

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