Why do free chlorine results differ on the SL1000 when compared to the powder pillow methods?

Document ID

Document ID TE8408

Published Date

Published Date 01/10/2018
Question
Why do free chlorine results differ on the SL1000 when compared to the powder pillow methods?
Summary
SL1000 results differ from powder pillow methods
Answer
There are a few factors that can result in differences in free chlorine results when comparing SL1000 results to powder pillow methods on colorimeters or spectrophotometers.
  • Chemkey reagents reduce many elements of human error or variability present in powder pillow tests: shaking time, reaction time, vial cleanliness, etc. 
    • Standardization of the measurement processes means that Chemkey results are more precise and repeatable.
  • Sample temperature: the SL1000 has automatic temperature control, eliminating differences in sample temperature which can result in variability.
  • Elimination of monochloramine interference: the free chlorine Chemkey has mitigated monochloramine as an interference in free chlorine tests; powder pillow methods still have this interference.
  • Elimination of outliers: the SL1000 takes multiple blank and sample measurements with each Chemkey, allowing the instrument to discard outliers and provide more accurate results.