Other Measurement Techniques
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      Chloramines and DPD 1

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

      DPD 1 is the most common reference measurement for determination of free chlorine.  It is important to understand the capabilities, influences, and limitations of DPD 1 against certain water quality variables like chloramines.  Please keep in mind that the presence of ammonia, and subsequently chloramines, will alter the final DPD 1 result.  Most DPD reagent manufacturers install a chemical inhibitor to restrict the detection of the chloramines, however this is usually destroyed within the recommended reaction time called for by the DPD 1 measurement instructions.  

      A simple, crude, but effective test...

      1. Take a DPD 1 measurement by following the procedure as called for 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 1 will not produce the accuracy required.  

      For more information, please contact your reference measurement supplier.