What is a common cause for the APA 6000 Ammonium/Nitrate Analyser reading high and erratically?

Document ID

Document ID TE6183

Version

Version 4.0

Status

Status Published

Published Date

Published Date 21/01/2019
Question
What is a common cause for the APA 6000 Ammonium/Nitrate Analyser reading high and erratically?
Summary
 Common cause for the APA 6000 Ammonium/Nitrate Analyser reading high and erratically.
Answer
Sample readings that are high and unstable may be due to air bubbles clinging to the ISE electrode membrane. Wetting the membrane with surfactant greatly reduces this problem. The easiest way to solve this problem is to substitute the analyser’s Surfactant Cleaning Solution (26974-53) for the sample. Disconnect the sample inlet tube from the bottom of the filtered sample bypass block, and place the tube in a container of cleaning solution; let the analyser "drink" from the container for about 30 minutes.