Determination of Nitrate Ion in Marine Biotopes with High Nitrate Content by Ultraviolet Spectrophotometry

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Abstract
A simple and rapid method for the determination of nitrate in seawater of high nitrate content (> 1 ppm) is proposed.The absorption of the nitrate ion is measured at 210 and 220 mμ. The sample is treated with a measured quantity of hydrochloric acid to eliminate the carbonate and bicarbonate interferences and measured against a nitrate free blank prepared by reduction of the nitrate to ammonia with Raney nickel. The addition of HCl permits also storage of the sample without special precautions and the use of the blank eliminates the most serious of the interferences (bromide) expected in sea‐water. The interference of organic matter limits however the applicability of the method to concentrations higher than 1 ppm.