Do Hach reagent sets for COD measure total or dissolved Chemical Oxygen Demand (COD)?

Document ID

Document ID TE4005

Published Date

Published Date 27/05/2017
Question
Do Hach reagent sets for COD measure total or dissolved Chemical Oxygen Demand (COD)?
Summary
Total or dissolved COD measurements.
Answer
The reagent sets sold by Hach are meant for total COD analysis. There is a digestion step that will break down all insoluble material and as a result, the method would be considered a total COD method.

To measure dissolved COD, filtration as a sample pretreatment step would remove suspended material. However, Hach does not have a recommendation on the type of filter necessary to measure dissolved COD as many filters could contribute to a COD measurement. The use of a centrifuge and decanting the supernatant liquid may also be a viable option for dissolved COD analysis.