Chloramines and DPD 1

Learn about how chloramines can interfere in your free chlorine DPD reference measurement.

DPD is the most common reference measurement for determination of free chlorine.  It is important to understand the capabilities, influences, and limitations of DPD  against certain water quality variables like chloramines.  Please keep in mind that the presence of ammonia, and subsequently chloramines, ambient light and atmospheric oxygen will alter the final DPD result.   

A simple, crude, but effective test...

1. Take a DPD measurement by following the procedure for free chlorine in your manufacturer's manual.
2. Take note of the resulting measurement. 
3. Keep the sample and wait an additional 30 seconds. 
4. Press "read" and take note of the resulting measurement. 
5. Repeat steps 3-4 again (and for as many times as you would like)
6. If chloramines are present, then the measurement will increase over time, and DPD will not produce the accuracy required.  

For more information, please contact your reference measurement supplier.