NITRATE MEASUREMENTS IN THE PRESENCE OF HIGH NITRITE CONCENTRATIONS1

Most accepted analytical procedures for nitrate in sea water become increasingly unreliable as tho nitrite concentration increases. We have developed an ozonation technique whereby nitrite is quantitatively oxidized to nitrate. In addition, we have formulated an equation to be used with the Mullin‐Riley (1955) reduction method when nitrite and nitrate are both present. This equation, unlike other recommended corrections, is based on demonstrated recoveries from known mixtures of nitrate and nitrite. In the ozone method the amount of nitrate produced is compared with the initial amount of nitrite. The difference in nitrogen, as determined by the two analyses, provides a method for estimating the quantity of nitrate originally present. Both the ozonation and numerical solutions appear particularly suited for studying nitrogen physiology of algal or bacterial cultures. Such studies often require analytical estimates for dissolved nitrate in the presence of high nitrite concentrations.