4.14  Determination of nitrate and ammonium in aerosol filters

Nitrate, ammonium (and chlorides) collected in an aerosol filter will not generally reflect the true air concentrations due to physical processes and chemical reactions on the filter, mainly with sulphuric acid. By adding the amount of ions in the aerosol filter to the amounts on alkaline and acid impregnated filters behind the aerosol filter, the sum of the concentrations of nitric acid and aerosol nitrate, ammonia and aerosol ammonium, and hydrochloric acid and aerosol chlorides can be determined. Separate determination of the gaseous and aerosol components can be achieved by use of denuders.

Extraction from aerosol filters is described in Section 3.6.

4.14.1  Determination of nitrate ions by ion chromatography

The analytical method is described in Section 4.1.

4.14.2  Spectrophotometric determination of nitrate by reduction to nitrite and reaction with sulphanilic acid

The analytical method is described in Section 4.3.1.

4.14.3  Automatic spectrophotometric determination of nitrate by reduction to nitrite and reaction with sulphanilic acid

The analytical method is described in Section 4.3.2.

4.14.4  Determination of ammonium ions by ion chromatography

The analytical method is described in Section 4.1.

4.14.5  Spectrophotometric determination of ammonium by the indophenol blue method

The analytical method is described in Section 4.4.1.

4.14.6  Automatic spectrophotometric determination of ammonium by the indophenol blue method

The analytical method is described in Section 4.4.2.


Last revision: November 2001