Preparation of the standard solutions of nitrate and their application to seawater and freshwater

Responding to the recommendation at the first Meeting of the International Coordination Group for the Cooperative Study of the Kuroshio and Adjacent Regions (CSK) 1965, a series of nitrate standard solutions consisting of eight different concentrations ranging from 0 to 50g-at NO₃-N/l in 30.5 sodium chloride solution with the highest purity was prepared for nitrate-N determination in seawater. The solutions have been proved to be stable at least 520 days after preparation.The best way of handling and conditioning the copper-cadmium column was studied for securing the perfect and reproducible conversion of nitrate to nitrite for the procedure as proposed byWood et al. (1967).It was also shown that the method can be applied to freshwater samples by the addition of sodium chloride and adjusting pH properly.