847 NITRATE, NITRITE AND AMMONIUM - FLOW INJECTION ANALYZER METHOD
NO3-N, NH4-N, NO2-N
Determination by flow injection analyzer.
Summary: This method involves the quantitative analysis of ammonium (NH4-N), nitrate (NO3-N) and nitrite (NO2-N) in water. Nitrate is determined by reduction to nitrite via a copperized cadmium column. This nitrite is then determined by diazotizing with sulfanilamide followed by coupling with N-(1-naphthyl)ethlyenediaminie dihydrochloride. The absorbance of the product is measured at 520 nm. Nitrite is determined in the same manner with the cadmium column off-line. Ammonia is heated with salicylate and hypochlorite in an alkaline phosphate buffer. The presence of EDTA prevents precipitation of calcium and magnesium and sodium nitroprusside is added to enhance sensitivity. The absorbance of the reaction product is measured at 630 nm and is directly proportional to the original ammonia concentration. The method has a detection limit of approximately 0.05 mg L-1 and is generally reproducible within 7%.
Note that the nitrate values reported include any nitrite in the sample. Nitrite is typically an insignificant fraction of the nitrate.
Wendt, K. 1999. Determination of Nitrate/Nitrite by Flow Injection Analysis (Low Flow Method). QuikChem Method 10-107-04-1-A. Lachat Instruments, Milwaukee, WI.
Switala, K. 1999. Determination of Ammonia by Flow Injection analysis. QuikChem Method 10-107-06-1-A. Lachat Instruments, Milwaukee, WI.