Can the CL17 Chlorine Analyser be used with seawater samples?

Document ID

Document ID TE3685

Version

Version 5.0

Status

Status Published

Published Date

Published Date 21/01/2019
Question
Can the CL17 Chlorine Analyser be used with seawater samples?
Summary
Inline measurement of chlorine in seawater with CL17
Answer
Although the CL17 is designed principally for the drinking water market, it has been successfully used for cooling water (ex: estuary make-up water) and seawater (ex: aquariums) applications. The successful application of the CL17 for these saline waters generally comes down to "good maintenance" and adequate sample flow.

The DPD chemistry used in the  CL17 is not affected by hardness levels up to 1000 mg/L CaCO3 (highest level tested), although there have been reports of analysers installed on treated cooling waters that have total hardness levels of greater than 5000 mg/L. The sample alkalinity must be below 400 mg/L CaCO3 when testing Free Chlorine, and below 700 mg/L CaCO3 when testing total chlorine.

If the sample alkalinity is questionable, a simple troubleshooting test can be performed to easily determine whether the analyser can tolerate the sample alkalinity. Adding 1 mL indicator solution and 1 mL of buffer solution to approximately 80-mL volume of the sample, then mixing and checking the resulting pH of the sample. If using the free chlorine reagents for the CL17, the final pH should be between 6.3 - 6.7 pH and if using the total chlorine reagents for the CL17, the final pH should be between 5.0 - 5.5 pH.

The DPD chemistry is not affected by sample temperature extremes between 5 - 50 degrees C.

The potential problems associated with using the CL17 in seawater or cooling water are related to crystal growth and subsequent "salting-out" in the colorimeter. If the sample is relatively particle-free (strained) and the sample flow is appropriate, this is not usually a problem. This application will most likely require more frequent cleaning of the colorimeter cell (possibly daily) with an acid/DI water flush which also helps prevent crystal growth.
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