Biomedical Engineering Reference
In-Depth Information
2.3.2.1
Time-Integrated Measurements
•
Personal nanoparticle sampler (PENS)
: A novel, active, PENS consisting of a respirable
cyclone and a micro-orifice impactor, with a cutoff aerodynamic diameter of 4 μm and
100 nm, which respectively enables the collection of the respirable particulate mass and
nanoparticles simultaneously, was developed to meet the critical demand for the personal
sampling of engineered nanomaterials in workplaces (Tsai et al., 2012).
•
Nano-MOUDI
: The Nano-MOUDI impactor collects particles ranging from >18 to
0.01 μm on 13 impaction stages. It can be used to characterize particle size distributions of
collected particles by mass. The morphology of the particles deposited on each impaction
stage can be further analyzed by using scanning electron microscope (SEM) or trans-
mission electron microscopy (TEM). Their crystallography, metal contents, and chemical
composition can be determined through further sample analysis techniques, such as x-ray
diffraction (XRD), atomic absorption spectrophotometer (AA), and gas chromatography/
mass spectrometry (GC/MS).
2.3.2.2
Time-Resolved Measurements
•
Codensation particle counter (CPC)
: The CPC is a real-time instrument used for measur-
ing particle number concentrations. Air is drawn into a saturator tube filled with super-
saturated isopropyl alcohol vapor. The vapor is condensed on air-containing aerosols, and
the aerosols grow until they can be sensed by a photodetector as they pass through a laser
beam. The CPC measures particles ranging from a few nanometers to a micrometer, with
measurable number concentrations ranging from 0 to 100,000 particles/cm
3
.
•
Scanning mobility particle sizer (SMPS)
: The instrument measures the particle size distri-
butions and number concentrations. The SMPS is composed of a differential mobility ana-
lyzer (DMA) and a CPC installed in series. The DMA first selects a particle size interval of
the sampled aerosol based on its electrical mobility in the scanning electric field, and then
the CPC counts the particles exiting into the classifier. It should be noted that the particles
must be previously neutralized at the DMA inlet using radioactive sources, generating
numerous positive and negative charges in order to reach a state of charge equilibrium. The
SMPS measures particles ranging from a few nanometers to a micrometer, with measur-
able number concentrations ranging from 10 to 760 nm.
•
Nanoparticle surface area monitor (NSAM)
: Recently, it has been found that the response
function curves of an electrical aerosol detector (EAD) (TSI Inc., Model 3070A, St. Paul,
MN, USA) matched with trancheobronchial (TB) and alveolar (A) depositions while the
ion trap voltages were set at 100 V and 200 V, respectively (Fissan et al., 2007). Based on
the above observations, the EAD was modified and a TSI NSAM (TSI Inc., Model 3550,
St. Paul, MN, USA) was built by adjusting its built-in, ion trap voltage. For an NSAM,
sampled particles are charged by a corona effect-induced ion diffusion at their surfaces.
The number of charges carried by a particle is related to its surface area (particle size). The
charged particles, after passing through the ion trap, are then collected on an electrical
filter, allowing the determination of the surface area concentration of collected particles.
The preset ion trap voltages of 100 and 200 V allow the concentrations of nanoparticle
surface area deposited in the tracheobronchial or alveolar region to be estimated, respec-
tively. The instrument measures the total surface area for particle diameters ranging from
10 to 1000 nm. This is good for measuring workplace exposure to nanoparticles and for
inhalation toxicology and epidemiology studies, but it does not provide the particle size
distribution and total surface area of the collected particles.
•
EAD and MEAD
: For EAD, sampled particles are first passed through a small cyclone
to remove particles with a diameter larger than 1.0 μm. The sampled aerosol flow (i.e.,
2.5 lpm) is then split into two: the portion of 1.5 lpm is directly introduced into the aerosol
charging chamber, and the other portion of 1.0 lpm is used as the carrier for unipolar ions,
