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Ammonia
Diagram
Specifications
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The diffusive sampler for ammonia collects gaseous ammonia by absorption on phosphoric acid. The amount of ammonia is determined spectrophotometrically by the indophenol method.

The passive samplers are composed of a polypropylene housing with an opening of 20 mm diameter. To reduce wind disturbance a teflon membrane is attached, supported by a wire net.

To protect the sampler from weather influences, as well as minimising wind disturbance, a protective shelter has to be used.

Diagram

Time series of a comparison of a continuous NH3 analyser and diffusion tube of ammonia [1].

 

Specifications

Samplingrate

31.5 ml/min at 20oC

Working range

0.5 — 20 µg/m3

Sampling time

2— 4 weeks

Detection limit

0.3 µg/m3 fortnight exposures

External influences:
   wind speed
 Influence of wind speed < 10% up to 4.5 m/sec
using protection shelters
   temperature
 no influence between 5 to 40oC
   humidity
no influence between 20 to 80%

Storage

before use: 4 months
after exposure: 2 months

Cross sensitivity

Solid particulates of ammonia are not collected

Expanded uncertainty*

27.4 % at concentration levels of 2 µg/m3

*according to GUM;
subject to change without notice
revised 3.1.2010

 
 
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