Removal of organic interferences in analysis of nitrate in water by UV spectroscopy.

Abstract

The determination of nitrate-nitrogen in water is difficult. The relatively complex procedure, the presence of interfering substances, and the limited concentration range of the various techniques all contribute to the difficulty. UV spectroscopy methods can be used, but they only determine approximate concentrations due to the organic compounds which can produce absorbances at the same wavelength as nitrate does. Once organic compounds can be removed, the accuracy of nitrate-nitrogen analysis by UV spectroscopy would be greatly improved. The main purpose of this research was to test methods for removal of organic compounds from water samples in order to improve the accuracy of the UV spectroscopy method for analysis of nitrate. Organic matter was not removed effectively by Prep-Sep C-18 Cartridges but was removed by XAD-4 resin. Pretreatment with XAD-4 produced results only slightly higher than the cadmium reduction method.