Usability of simplified UV–Vis spectrophotometric methods for the determination of nitrate in the presence of organic matter and chloride as interfering factors

The presence of nitrate in groundwater and surface water in concentrations above levels suitable for human consumption is an increasingly common problem. This is mainly due to human activity, such as the excessive use of fertilizers and the inadequate deactivation of pits. Water analysis laboratories very often carry out analyses to determine nitrate to control the presence of this anion in water intended for human consumption. One of the most commonly used methods is spectrophotometry, both with commercially available kits and by direct measurement of specific wavelengths. However, in these methods, the presence of organic matter and chloride can influence the results obtained. Thus, in this study, the applicability of the simplification (without acidification) of two methods for the determination of nitrate in water by ultraviolet–visible absorbance was verified in the presence of the above-mentioned interfering factors, and it was found that the absorbance method at 220 nm corrected for the absorbance at 275 nm, in its simplified form without acidification, can be used with concentrations of organic matter of 20 mg L−1 for high nitrate concentrations (10 mg L−1 NO3-N).