Determination of ammonium-, nitrite- and nitrate-nitrogen by molecular emission cavity analysis using a cavity containing an entire flame

Abstract

Ammonium-, nitrite- and nitrate-nitrogen were determined by molecular emission cavity analysis using a cavity containing an entire flame. Ammonium-nitrogen was converted to ammonia by injection on to solid sodium hydroxide. The calibration graph was linear for 5–100 µg ml^–1 of nitrogen when the ammonia generated was swept directly into the cavity and for 0.05–1.0 µg ml^–1 of nitrogen when it was collected in a liquid nitrogen cold-trap. Concentrations of 1.5 and 0.01 µg ml^–1 of nitrogen could be detected using the direct and cold-trap methods, respectively. Nitrite was determined after conversion to nitrogen monoxide by iodide. Nitrate was reduced to nitrite using a copperised cadmium column and then determined as nitrite. The calibration graphs for both anions were linear up to 7 µg ml^–1 of nitrogen and 0.1 µg ml^–1 of nitrogen could be detected. The methods were applied successfully to the determination of nitrite and nitrate in meat products, and nitrate-nitrogen in drinking water samples.