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. The 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 determined by heating with salicylate and hypochlorite in an alkaline phosphate buffer. The presence of EDTA prevents precipitation of calcium and magnesium. Sodium nitroprusside is added to enhance sensitivity. The absorbance of the reaction product is measured at 660 nm and is directly proportional to the original ammonia concentration. The method has detection limits of approximately 0.05 mg/L for all analytes.
Note that the nitrate values reported include any nitrite in the sample. Nitrite is typically an insignificant fraction of the nitrate.
Sample amount requested: 20 mL for Nitrate and/or Ammonium; 20 mL for Nitrite Questions concerning limited sample size can be answered by the UC Davis Analytical Laboratory.
Hofer, S. 2003. Determination of Ammonia (Salicylate) in 2M KCl soil extracts by Flow Injection Analysis. QuikChem Method 12-107-06-2-A. Lachat Instruments, Loveland, CO.
Knepel, K. 2003. Determination of Nitrate in 2M KCl soil extracts by Flow Injection Analysis. QuikChem Method 12-107-04-1-B. Lachat Instruments, Loveland, CO.
Method 4500-NO3 I. Cadmium Reduction Flow Injection Method (Proposed) in Standard Methods for the Examination of Water and Wastewater, 20th Edition. Clesceri, L. S.; Greenberg, A. E.; and Eaton, A. D.; eds. American Public Health Association; Washington DC; 1998. pp. 4-121 - 4-122.
Method 4500-NH3 H. Flow Injection Analysis (PROPOSED) in Standard Methods for the Examination of Water and Wastewater, 20th Edition. Clesceri, L. S.; Greenberg, A. E.; and Eaton, A. D.; eds. American Public Health Association; Washington DC; 1998. pp. 4-111 – 4-112.