How can manganese interference in a DPD chlorine test be eliminated?

Document ID

Document ID TE1570

Published Date

Published Date 06/15/2022
Question
How can manganese interference in a DPD chlorine test be eliminated?
Summary
Eliminating manganese interference in DPD chlorine analysis
Answer
Manganese interference can be eliminated using potassium iodide and sodium arsenite.

The sample is tested twice: once with pretreatment and once without. Testing the sample without pretreatment will give a result due to chlorine and oxidized manganese (and oxidized chromium).Testing the sample with pretreatment will give a result due to the oxidized manganese (and oxidized chromium) without chlorine. Subtraction then gives the true chlorine value.

The pretreatment procedure is given in the interference section of the DPD chlorine methods, and is copied below:



The potassium iodide and sodium arsenite, used in the pretreatment process, work together to remove chlorine from the sample.

As an alternative, manganese interference can be eliminated by switching to the US ENG Chlorine, Free, Indophenol Method 10241, Powder Pillows_DOC316.53.01256 for free chlorine.
 

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