Iodometric colorimetry is applied for measuring COD(Mn), using hydrogen peroxide as the mediator. It saves time, space, and chemicals without degradation of accuracy. The method can be applied to any digestion method which uses permanganate. The remaining permanganate is reduced by hydrogen peroxide at pH 1-2, where the peroxide is stable. If the silver ion for masking halides remains in the digested mixture, it is made to settle on the reduction by an excess of sodium chloride. The supernatant of digested mixture is transferred to 0.3M KI in the acetate buffer (pH 5-6) which contains molybdate (catalyst). As the peroxide oxidizes iodide within 2 min, the formed triiodide is colorimetrically measured at 353nm within 2h of reaction. Blank increase by air oxidation can be ignored during this time. The method of controlling the pH of the reaction mixture is also described.
- Nippon Suisan Gakkaishi is an official journal of the Japanese Society of Fisheries Science written in Japanese only.
The society publishes an English journal, Fisheries Science, as well, which accepts submissions from non-members of the society over the world. Detailed information is available in http://jsfs.jp/en/journals/fisheries-science.