If the sample water contains further oxidizing agents, these will react like bromine and
contribute to the measurement result.
The DPD reagent buffers the pH value of the sample water in the range of 6.2 to 6.5, which is
essential for colour development. If the sample water is very alkaline or acidic, this must be
adjusted to a pH within the range of 6 to 7 by addition of 0.5 mol/l sulphuric acid or 1 mol/l
caustic soda, respectively, before the DPD reagent is added.
T12/204 T12/204