Determination of ammonium- and nitrate-nitrogen by molecular emission cavity analysis

Abstract

Ammonium nitrogen is determined at parts per million to percentage levels by injecting the sample solution on to solid sodium hydroxide in a small vial. The ammonia generated is swept by nitrogen into a molecular emission cavity analysis (MECA) oxy-cavity and the intensity of the NO—O continuum is measured at 500 nm. The method is rapid, precise and free from interferences and has been applied successfully to the determination of ammonium ions in fertilisers, river waters and sewage samples. Nitrate ions can also be determined after reduction to ammonia by Devarda's alloy.