silicon and silicon-tetrachloride

A new method was developed for the preparation of highly monodisperse isotopically enriched Si-29 silica nanoparticles ((29)Si-silica NPs) with the purpose of using them as spikes for isotope dilution mass spectrometry (IDMS) quantification of silica NPs with natural isotopic distribution. Si-29 tetraethyl orthosilicate ((29)Si-TEOS), the silica precursor was prepared in two steps starting from elementary silicon-29 pellets. In the first step Si-29 silicon tetrachloride ((29)SiCl4) was prepared by heating elementary silicon-29 in chlorine gas stream. By using a multistep cooling system and the dilution of the volatile and moisture-sensitive (29)SiCl4 in carbon tetrachloride as inert medium we managed to reduce product loss caused by evaporation. (29)Si-TEOS was obtained by treating (29)SiCl4 with absolute ethanol. Structural characterisation of (29)Si-TEOS was performed by using (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy and Fourier-transform infrared (FTIR) spectroscopy. For the NP preparation, a basic amino acid catalysis route was used and the resulting NPs were analysed using transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), dynamic light scattering (DLS) and zeta potential measurements. Finally, the feasibility of using enriched NPs for on-line field-flow fractionation coupled with multi-angle light scattering and inductively coupled plasma mass spectrometry (FFF/MALS/ICP-MS) has been demonstrated.

Topics: Chlorides; Fractionation, Field Flow; Indicator Dilution Techniques; Isotopes; Mass Spectrometry; Nanoparticles; Scattering, Small Angle; Silanes; Silicon; Silicon Compounds; Silicon Dioxide; X-Ray Diffraction

The reactive airway dysfunction syndrome (RADS) is a recently described syndrome in which bronchial hyperreactivity and asthmatic symptoms develop in previously healthy individuals after a single large exposure to an irritating gas, fume, or vapor. We report a cluster of three Philadelphia police officers who developed RADS after a common exposure to toxic fumes from a roadside truck accident. Results of initial pulmonary function testing were normal in all three, and methacholine challenge was required for diagnosis in two out of the three. This syndrome needs to be recognized by physicians dealing with environmental or industrial medicine as a potential cause of loss of work or inability to perform on the job. Also, there is a potential for multiple individuals to develop this syndrome from a single incident.

Topics: Accidents, Traffic; Adult; Asthma; Bronchial Provocation Tests; Chlorides; Forced Expiratory Volume; Humans; Male; Middle Aged; Silanes; Silicon; Silicon Compounds; Sodium Hydroxide; Vital Capacity