What could be the cause of inconsistent results using the ultra low range hardness chlorophosphonazo colorimetric methods?

Document ID

Document ID TE296

Version

Version 2.0

Status

Status Published

Published Date

Published Date 27/05/2017
Question
What could be the cause of inconsistent results using the ultra low range hardness chlorophosphonazo colorimetric methods?
Summary
Inconsistent results with the ultra-low range hardness chlorophosphonazo method
Answer
For best results: Confirm proper pretreatment of the labware and it is recommended to dedicate that labware to the ultra-low range (ULR) hardness method only. Wash the sample cell or pour-thru cell well with high purity water to eliminate all traces of CDTA from the previous sample. Carry-over of CDTA to the next sample will cause low results. Labware should always be covered or stored in a dust-free environment when not in use.