Is distillation necessary when using an ion selective electrode for ammonia determination?

Dokument-ID

Dokument-ID TE8622

Veröffentlichungsdatum

Veröffentlichungsdatum 20.09.2018
Frage
Is distillation necessary when using an ion selective electrode for ammonia determination?
Zusammenfassung
Distillation for ammonia determination with ion selective electrode
 
Antwort
Distillation may be needed when using an Ion Selective Electrode for ammonia determination if certain compounds are present. Dirty samples that contain surfactants or fatty acids may damage the membrane, leading to unstable readings. An air-gap assembly can be used to help prevent membrane damage from these contaminates as an alternative to distillation. Amines, mercury, and silver are direct interferences for the ammonia electrodes. If these analytes are present, distillation is necessary to remove them from the sample. An air gap assembly is not effective for preventing inorganic interferences from complexing with ammonia.

For EPA reporting, a regulator should be consulted as manual distillation may not be required if comparability data on representative samples show that the distillation is not necessary. Manual distillation is necessary to resolve controversies.
 

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