DETERMINATION OF NITRATE IN RAW, POTABLE AND WASTE-WATERS BY ULTRAVIOLET SPECTROPHOTOMETRY

A method is proposed for the determination of nitrate in raw, potable and waste waters using ultraviolet spectrophotometry. The use of an activated carbon filter at an elevated pH eliminates interference from organic matter, i.e., substances commonly assumed to be responsible for the related absorbances at 275 and 210 nm. The procedure also removes the interferences of several cations that are precipitated out of solution. The development work leading up to the proposed method is discussed with reference to the relevant behaviour towards organic matter and the nitrate ion of activated carbon materials. The method has a limit of detection of 0.006 mg 1-1 N and a total standard deviation of 0.016 mg 1-1 N at a nitrate concentration of 1.05 mg 1-1 N in potable water. No statistically significant difference was detected between the proposed method and an established automated method for a wide range of samples.