What could cause the sample to turn turbid or begin effervescing after the addition of the DPD reagent?

Document ID

Document ID TE209

Version

Version 4.0

Status

Status Published

Published Date

Published Date 09/27/2018
Question
What could cause the sample to turn turbid or begin effervescing after the addition of the DPD reagent?
Summary
Turbid or Effervescing sample after adding DPD
Answer
Samples with high alkalinity might turn turbid or begin effervescing. Check the alkalinity of the sample. It is common for samples over a pH of 7.6 to have alkalinity of 250mg/L and above. When adding DPD, you should get a pH around 6.3. High amounts of bicarbonate can cause small bubbles in the sample, causing false high readings. If possible, pretreat water to a pH of 6-7 before testing.

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