Biomedical Engineering Reference
In-Depth Information
size-resolved real-time monitors and size-resolved samplers, which increase the ease
of use, since combination of devices can be avoided. Examples are (a) a wide-range
real-time classifier (10 nm-27 µm) (mobility + optical detection), (b) a nano aerosol
classifier and short/long term sampler system (20-450 nm), and (c) a low-cost total
(active) surface area monitor.
The mentioned portable online devices all determine physical parameters like
number, surface area, or mass concentrations. No portable devices detecting (size
resolved) chemical composition or particle morphology are yet available. So far
only transportable devices like aerosol mass spectrometer exist but have not been
employed at workplaces yet. Instruments being capable of delivering this infor-
mation are important to facilitate the fast discrimination of product nano-objects/
NOAA from background particles. Therefore, sampling devices for personal and
areal measurements are currently often employed to allow such discrimination.
(Personal) samplers collect the aerosol fraction that can penetrate into only one
or all compartments of the human respiratory tract. The samplers try to emulate
one or more of the sampling conventions which are based on the entry efficiency
of particles in the respiratory tract, for example, EN ISO 13138. With respect to
nanoparticle sampling in workplaces, Tsai et al. (2012) have developed an active
Personal Nanoparticle Sampler (PENS) that consists of an impactor that is mounted
downstream of an existing cyclone for the respirable fraction. The impactor has an
aerodynamic cut-size of 100 nm and is followed by a back-up filter. Slightly earlier,
Furuuchi and coworkers (Furuuchi et al. 2010) have developed a personal nanosam-
pler based on another principle, that is, impaction in a layered metal fibre mesh filter.
Very interesting are the developments that match the ICRP/ISO criteria (EN ISO
2012) for respiratory tract compartment specific lung-deposited fractions, which
enable interpretation of the results with respect to the lung-deposited dose. Cena et al.
2011 have developed an add-on device to the SKC personal aluminum cyclone for the
respirable fraction. This sampler is called the Nanoparticle Respiratory Deposition
(NRD) sampler and consists of two stages. The sampler is inserted between the
cyclone outlet and the usual 37-mm filter cassette. Its first stage is an impactor with
a cutoff of 0.3 µm, and the total pressure drop is low enough to allow a normal per-
sonal sampling pump. The final stage emulates the total deposition by diffusion in
all compartments of the respiratory tract.
Within the NANODEVICE projects, a number of prototype instruments were
developed aiming to meet these conventions; for example, (a) a wide-range size
resolving personal sampler (2 nm-5 µm) up to 8 size fractions; (b) a sampler for
aerosol fraction deposited in the gas-exchange region (20 nm-5 µm), 8 size classes;
and (c) a sampler for aerosol fraction deposited by diffusion in the anterior nasal
region 5-400 nm (www.nano-device.eu).
In the case of sampling directly through a substrate suitable for electron microscope
techniques (EM), for example, silicon substrates or Transmission Electron Microscopy
(TEM) grids, three different collection principles can be observed: (a) particles are
deposited by diffusion directly from the air stream passing through the grid open-
ings, (b) particles are deposited onto a substrate by an electric field, or (c) particles are
deposited by thermophoresis. Many versions of the first principle are also available as
personal samplers, for example, the Aspiration Electron Microscopy Sampler designed
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