Elimination of interferences in the colorimetric analysis of ammonium in water and soil extracts

The manual method for analyzing ammonium (NH4) in water and 1 M potassium chloride soil extracts using the Berthelot reaction was studied with the goal of eliminating interferences from commonly found ions. Three complexing agents at varying concentrations were evaluated. A 12% solution of sodium citrate was found to eliminate normal interferences in soil extracts and natural waters and was chosen as being the best of the three. Using sodium citrate as one component of the method, each component or parameter of the method was studied to be sure the maximum sensitivity was achieved.