Application Note

Water Analysis Using LAMBDA UV-Visible Spectrophotometers: Nitrate-Nitrogen Determination


Nitrate ions react with 2,6-dimethyl phenol (DMP) in sulfuric and phosphoric solution to form 2,6-dimethyl-4-nitrophenol (Figure 2) which can be detected spectrophotometrically at 340 nm and is directly proportional to the nitrate-nitrogen concentration. The Merck test kit allows the concentration to be determined without the use of a calibration curve by multiplying the measured absorbance at 340 nm by a known factor. In this application, the quantitative analysis of nitrate was performed using the LAMBDATM 265UV-Vis spectrophotometer and Merck Spectroquant® cell test. The method used is analogous to DIN 38405-9.