Ammonia-nitrogen (NH3-N) occurs naturally in groundwaters at concentrations below 0.2 mg/L and up to 12 mg/L in surface waters, as a result of decomposition of organic matter. High concentrations of ammonia in surface waters are toxic to aquatic life and are indicative of contamination from industrial effluent, raw sewage and agricultural runoff. Ultimately the pH value of the water determines whether ammonia-nitrogen is found as NH4+, NH4OH or NH3. 1 In this application, the quantitative analysis of ammonia-nitrogen was performed using the LAMBDA 265™ UV/Vis spectrophotometer and CHEMetrics ammonia nitrogen cell test.