845 NITRATE AND AMMONIUM - DIFFUSION-CONDUCTIVITY ANALYZER METHOD
NO3-N, NH4-N
Determination by diffusion-conductivity analyzer.
Summary: This method involves the quantitative analysis of ammonium (NH4-N) and nitrate (NO3-N) in water. Ammonium and nitrate are measured by the diffusion-conductivity method based on the gaseous diffusing of ammonia (NH3) across a gas permeable membrane in the presence of excess base (KOH) and subsequent conductivity detection. Samples can be stored for up to three weeks at low temperature (<4°C). For longer term storage, toluene or thymol should be added to the sample to prevent microbial growth. The method has detection limit of approximately 0.05 mg L-1 and is generally reproducible within 7%.
Carlson, R. M. 1978. Automated separation and conductimetric determination of ammonia and dissolved carbon dioxide. Anal. Chem. 50:1528-1531.