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The sampler is based on that of Palmes [1] and is
a passive device requiring no power for its operation. It
collects NO2 by molecular diffusion along an inert
tube to an absorbent, in this case triethanolamine. The
sampler, which is shown in the following diagram, consists of
a polypropylene tube; the collected NO2 is
determined spectrophotometrically by the well-established
Saltzmann method. The samplers are placed in a special shelter
to protect them from rain and minimize the wind influence.
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Diagram
The diagram shows the comparison of yearly
averages of NO2 diffusive samplers and NO2
measurements of different continuous monitoring sites [2] in
Switzerland. Each point is characterized by 50 to 70 diffusive
sampler measurements over one year and a complete data set of
continuous chemiluminescence monitors.
Specifications
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Samplingrate |
0.8536 ml/min corrected to 9oC
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Working range |
1 — 200 µg/m3
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Sampling time |
1 — 4 weeks |
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Detection limit |
0.64 µg/m3
for 2-week exposure |
| External
influences: |
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wind
speed
turbulences at kerbsites |
influence of wind speed < 10% up to
4.5 m/sec
using protection shelters
may rise uptake rate,
membranes recommended
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temperature |
no influence between 5 to
40oC |
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humidity
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no influence between 20 to 80%
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Storage |
before
use: 12
months
after exposure: 4
months |
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Cross sensitivity |
nitric oxide and sulfur dioxide do not
interfere
peroxyacetyl nitrate will give higher
results [ 4] |
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Expanded uncertainty* |
18.7 % at
concentration levels of 20 - 40 µg/m3
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*according to GUM;
subject to change without
notice |
revised 3.1.2010
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