What are the interferences for Total Alkalinity, Colorimetric Method, TNTplus 870, Method 10239?

Document ID

Document ID TE102

Published Date

Published Date 08/01/2019
Question
What are the interferences for Total Alkalinity, Colorimetric Method, TNTplus 870, Method 10239?
Summary
Interferences to the Alkalinity TNT870 (colorimetric) method 10239
Answer
Samples with an acid capacity above 8 mmol/L must be diluted with deionized (DI) water that contains no carbon dioxide (CO 2). One can remove CO 2 from water by boiling. The absence of CO 2 in the water used for dilution can be checked by carrying out a blank measurement. If the samples have high buffering capacity, dilute with DI water. CO 2 in the DI water will interfere when diluting samples or standards for this colorimetric test. The CO 2 free water is not as critical in the titration as with the colorimetric procedure. The colorimetric test is more sensitive to slight changes in CO 2 concentration due to the colorimetric detection and small sample volume used. 

Something else to note: the reagents in the TNT+ vials are dry, so it is important to invert several times to dissolve the powder.