Bio-Concentrators Overview Originally designed for the
detection of airborne biological agents, the Bioconcentrators
Models 4220 and 4240 are high-performance particle
concentrating aerosol samplers which can be used in any
application where particle concentration presents a problem.
In many cases of particle
sampling from ambient air, the concentration of airborne
particles is so low that it becomes necessary to sample for
prolonged periods of time in order to obtain sufficient mass for
chemical or biological characteristion.
One such case is the
identification of biological aerosols by mass spectrometry. In
this application, the aerosol sampler delivers a representative
sample of the airborne particles to a pyrolysis tube which,
periodically, converts the sample thermally and chemically to
components that are then analysed by mass spectrometry.
The mass rate of delivery of
material to the pyrolysis tube must be sufficient to allow the
detection of biological aerosols with a concentration of about 1
particle per litre of air.
At the same time, in certain
situations, any delay in analysis is to be avoided. Indeed, a
response time in the order of minutes is desired. As a result, a
need arises for a device capable of concentrating
particles from several hundred litres per minute of air into a
low flow rate compatible with the spectrometric
technique outlined above.
The Bioconcentrator draws air at
300 L/min from the surrounding environment and then splits the
air into a particle-rich stream and a particle-depleted reject
stream.
The resulting particle-rich
stream contains only 0.3% of the inlet air i.e., 1 L/min, but up
to 90% of the ambient particles in the size range 2.5-10 microns
in the case of Model 4220 thus increasing the sensitivity of the
analysis by up to 300 times (1-10 microns in the case of Model
4240).Bio-Concentrators Specifications
Bio-Concentrators Design The Biocentrator is effectively
a three-stage virtual impactor. In a
conventional impactor, particles with sufficient inertia (size)
strike a collection plate where they remain for later analysis.
In a virtual impactor, particles are drawn through a series of
nozzles and upon exiting these nozzles encounter a receiving tube.
The design is such that those
particles with sufficient inertia (above the desired cut-point)
continue forward with a small portion of the flow into the
receiving tube whilst the rest of the flow carrying only small
particles below the cutpoint is diverted around the receiving
tube.
Ambient air is sampled at 330 L/min
through an initial impactor (inlet scalper) which removes
particles larger than 10 microns and discards them together with
30 L/min of the air flow.
The remaining 300 L/min sampled
air flow then passes through a two-stage concentrating virtual
impactor (CVI) which concentrates particles in the 2 to 10 micron
(or 1 to 10) diameter ranges into a single 1 L/min stream for
output to an external collector or detector (not provided).
Two lightweight, high
performance vacuum pumps draw the inlet air flow through the
system. The air flow streams are precisely balanced and no valves
are used to control the flow.
The Concentrator measures 356 x
394 x 254 mm and weighs 16 kg.Bio-Concentrators Features
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