|
The diffusive sampler is based on the diffusion of
ozone along a tube to an absorbing medium. The chemisorption of
ozone takes place by reaction with 1,2-di(4-pyridyl)-ethylene (DPE);
the ozonide formed undergoes cleavage and yields an aldehyde. The
amount of aldehyde is finally determined spectrophotometrically
by the MBTH method at 442 nm.
The diffusive sampler for ozone consists of a polypropylene
tube. At the closed end there is a glass fiber filter dipped in
a solution of DPE in acetic acid.
To protect the samplers against weather conditions
and to eliminate the light effect on DPE, a special shelter was
developed.
Diagram
The figure shows the result of an intercomparison
of integrated ozone methods in the Euopean Alps. The results are
averaged over 6 monitoring sites at various heights from 100 to
1780 m above sea level [3].
Specifications
|
Samplingrate
|
PS [mabs] = 0.0255 [mg/m3 . h] r
= 0.83
|
|
Working range
|
5
– 240 µg/m3
|
|
Sampling time
|
1
to 2 weeks
|
|
Detection limit
|
5.1 µg/m3 weekly exposures
|
| External
influences: |
|
wind
speed
|
influence
of wind speed < 10% up to 2.0 m/sec
using protection shelters |
|
temperature
|
no
influence between 10 to 30oC |
|
humidity
|
no influence between 20 to 80% |
|
Storage
|
before use:
6 months
after exposure: 4 months
|
|
Cross sensitivity
|
oxidants
|
|
Expanded uncertainty*
|
20.3 % at concentration levels
> 80 µg/m3
|
|
|
*according to GUM;
subject to change without notice |
revised 3.1.2010
|
|
