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.
If the sample water contains high concentrationvalues of active oxygen, a measured value of 0
mg/l can be displayed. In that case, a dilution is recommended.
T2/204 T2/204