The removal of the organic interference in the analysis of nitrate-nitrogen in waters by the ultraviolet spectrophotometric screening method.

Abstract

The determination of nitrate-nitrogen in water is difficult at best. The relatively complex procedures, the presence o~ interfering substances, and the limited concentration ranges of the various techniques all contribute to the difficulty. Screening methods can be used, but they only determine approximate concentrations. Once a sample has been screened, a method suitable for its concentration range must then be selected. If an easier method were available, or if an improvement on an existing method could be made, the nitrate-nitrogen analysis would be greatly facilitated. The main purpose of this research is to refine and test the use of activated charcoal for the removal of the organic interference in various water samples. This removal would eliminate the unreliable organic corrections and would permit accurate analysis of nitrate-nitrogen by ultraviolet spectroscopy. A method of analysis using activated charcoal is proposed. The chromotropic acid method will be used as the reference/comparison method. The chromotropic acid method and the ultraviolet spectrophotometric screening method can both be found in the Standard Methods for the Examination of Water and Wastewater, 15th ed., 1980.