Two bronze medals for Switzerland at the 43rd International Chemistry Olympiad in Ankara, Turkey.

At the 2011 International Chemistry Olympiad in Ankara, with 71 participating countries, Switzerland achieved two bronze medals thanks to two outstanding students.

Cerium oxide nanoparticle uptake kinetics from the gas-phase into lung cells in vitro is transport limited.

Nowadays, aerosol processes are widely used for the manufacture of nanoparticles (NPs), creating an increased occupational exposure risk of workers, laboratory personnel and scientists to airborne particles. There is evidence that possible adverse effects are linked with the accumulation of NPs in target cells, pointing out the importance of understanding the kinetics of particle internalization. In this context, the uptake kinetics of representative airborne NPs over 30 min and their internalization after 24 h post-exposure were investigated by the use of a recently established exposure system. This system combines the production of aerosolized cerium oxide (CeO(2)) NPs by flame spray synthesis with its simultaneous particle deposition from the gas-phase onto A549 lung cells, cultivated at the air-liquid interface. Particle uptake was quantified by mass spectrometry after several exposure times (0, 5, 10, 20 and 30 min). Over 35% of the deposited mass was found internalized after 10 min exposure, a value that increased to 60% after 30 min exposure. Following an additional 24 h post-incubation, a time span, after which adverse biological effects were observed in previous experiments, over 80% of total CeO(2) could be detected intracellularly. On the ultrastructural level, focal cerium aggregates were present on the apical surface of A549 cells and could also be localized intracellularly in vesicular structures. The uptake behaviour of aerosolized CeO(2) is in line with observations on cerium suspensions, where particle mass transport was identified as the rate-limiting factor for NP internalization.

No evidence for cerium dioxide nanoparticle translocation in maize plants.

The rapidly increasing production of engineered nanoparticles has raised questions regarding their environmental impact and their mobility to overcome biological important barriers. Nanoparticles were found to cross different mammalian barriers, which is summarized under the term translocation. The present work investigates the uptake and translocation of cerium dioxide nanoparticles into maize plants as one of the major agricultural crops. Nanoparticles were exposed either as aerosol or as suspension. Our study demonstrates that 50 µg of cerium/g of leaves was either adsorbed or incorporated into maize leaves. This amount could not be removed by a washing step and did not depend on closed or open stomata investigated under dark and light exposure conditions. However, no translocation into newly grown leaves was found when cultivating the maize plants after airborne particle exposure. The use of inductively coupled mass spectrometer allowed detection limits of less than 1 ng of cerium/g of leaf. Exposure of plants to well-characterized nanoparticle suspensions in the irrigation water resulted also in no detectable translocation. These findings may indicate that the biological barriers of plants are more resistant against nanoparticle translocation than mammalian barriers.

Ion-selective supported liquid membranes placed under steady-state diffusion control.

Supported liquid membranes are used here to establish steady-state concentration profiles across ion-selective membranes rapidly and reproducibly. This opens up new avenues in the area of nonequilibrium potentiometry, where reproducible accumulation and depletion processes at ion-selective membranes may be used to gain valuable analytical information about the sample. Until today, drifting signals originating from a slowly developing concentration profile across the ion-selective membrane made such approaches impractical in zero current potentiometry. Here, calcium- and silver-selective membranes were placed between two identical aqueous electrolyte solutions, and the open circuit potential was monitored upon changing the composition of one solution. Steady state was reached in approximately 1 min with 25-microm porous polypropylene membranes filled with bis(2-ethylhexyl) sebacate doped with ionophore and lipophilic ion exchanger. Ion transport across the membrane resulted on the basis of nonsymmetric ion-exchange processes at both membrane sides. The steady-state potential was calculated as the sum of the two membrane phase boundary potentials, and good correspondence to experiment was observed. Concentration polarizations in the contacting aqueous phases were confirmed with stirring experiments. It was found that interferences (barium in the case of calcium electrodes and potassium with silver electrodes) induce a larger potential change than expected with the Nicolsky equation because they influence the level of polarization of the primary ion (calcium or silver) that remains potential determining.