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This paper describes two improvements of the amperometric titration method (Standard Method4500-ClOsub2/sub E) for chlorite residual analysis and discusses the interference of nitrite with thismethod. First, the addition of starch solution into water samples provides a color indicator of thetitration end point, aiding the ease of analysis. Second, DPD total chlorine measurements can beused to check the titration accuracy in the method's chlorine titration step. Nitrite was found tocause significant interferences with the amperometric titration method, yet this interference hasbeen largely ignored in practice. This study investigated the magnitude of the nitriteinterference; possible mechanisms are discussed herein. If nitrite levels exceed 0.04 mg/L asnitrogen, other chlorite analysis methods such as ion chromatography and colorimetric methodsare preferred due to the possible nitrite interference with the amperometric method. A Hachcolorimetric method using Horseradish Peroxidase/Lissamine Green B reagent (similar to U.S. Environmental Protection Agency Method 327.0) was beta-tested in parallel with the amperometric titration method. Although theHach colorimetric method will not likely come to market as indicated by Hach Company, themethod was useful in identifying the analytical interferences of the amperometric method. Includes 9 references, table, figures.

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Edition: Vol. - No. Published: 11/01/2007 Number of Pages: 12File Size: 1 file , 120 KB