Conductivity Detector Cell Issue

[5kyul]

Dear Community,

We had an issue with the conductivity detector, so I am looking for any idea and/or related troubleshooting experience. What happened is that the baseline signal is periodically decrease (up to 0.2 µS) and comes back up over a span of 20-30 min in every 30-60 min, please find attached screenshots. After replacing the cell, the issue is gone now but we would like to know what whould have caused this in order to prevent a reoccurrence of it. Any idea or experience with the similar issue are very much appreciated. Please let me know!

Thank you 😁

Kind regards,

Sue

[GeorgeTFS · Accepted solution]

Hello @5kyul I received a response from the science team. Based on the information you provided, they responded that it could be that there was a loose ferrule or fitting, as the pattern is very repetitive. However, they added that if you could share the chemistry you were using, they may be able to provide additional answers. Please let me know if this helps.

[The_Ion_Lady · Accepted solution]

Hello @5kyul,

Interesting, it looks like there might be some contaminant stuck in the CD cell which causes the changes in conductivity. Usually, this can happen with old cells with air bubbles but sometimes it could be something that has crashed out & stuck in there. With air bubbles, you can usually "burp" (https://www.youtube.com/watch?v=OuJBTDOL7RM) the cell and it will clear it. However, if it's a contaminant then it is more difficult.

I hope that helps for the future but it would be good to see the Chromeleon backup file as they can hold amazing amount of information for the sequence/run/method.

Good-luck!

[GeorgeTFS]

Thank you, @5kyul, for your question. We will work to get you an answer ASAP. 
@The_Ion_Lady and @chris-shevlin can you please assist?

[GeorgeTFS · Accepted solution]

Hello @5kyul I received a response from the science team. Based on the information you provided, they responded that it could be that there was a loose ferrule or fitting, as the pattern is very repetitive. However, they added that if you could share the chemistry you were using, they may be able to provide additional answers. Please let me know if this helps.

[5kyul]

Hello @GeorgeTFS thank you very much for the reply. I did not imagine that a loose ferrule or fitting could cause such slow drift in baseline. I always thought it would be more rapid, thanks for the idea! This issue occurred on ICS2100 which is equipped with KOH eluent generator during anion analysis. The eluent strength is set differently as we tested different columns and observed their behavior hoping the issue is specific to a certain column. However the same drifted baseline was observed which was not resolved until we replaced the cell. For example of chromatographs that I attached on this post, the top screenshot was taken with 38mM KOH with AG/AS-18 column and the middle and bottom ones were with 14mM KOH and AG/AS19.

[GeorgeTFS]

Thank you @5kyul  for providing additional info. I will pass it along to the team. 

[GeorgeTFS]

Hello @5kyul.  I have some additional info from the team.

PREVIEW

From looking at the original screenshots it is symptomatic of a micro void in the fittings around the CD cell. We talked about the latest response and obtaining a cmbx Chromeleon back up file to get a better understanding of anything related to this issue. I have attached a simple step by step guide on how to back up a this data and also the audit trail as it is an excellent source of troubleshooting to see when the issue first occurred and anything abnormal happened or related to the void dips.

From the screenshots sent in and the additional update below it appears that when the CD cell was changed the issue was resolved. This would entail the fittings being removed from the CD cell and once the new CD cell installed the fittings were connected and re-seated. It would be interesting to understand as a quick check if the old cell can be re installed to see if it is faulty or ok after a sensible equilibration time overnight. Also did the customer re prime the pump after changing the CD cell? This can also be better understood with the Chromeleon back up of when the issue first occurred.

Please see the attached step-by-step guide for creating a backup file and also instructions on how to create an audit trail backup.

If this information helped you resolve the issue, please let me know.

[The_Ion_Lady · Accepted solution]

Hello @5kyul,

Interesting, it looks like there might be some contaminant stuck in the CD cell which causes the changes in conductivity. Usually, this can happen with old cells with air bubbles but sometimes it could be something that has crashed out & stuck in there. With air bubbles, you can usually "burp" (https://www.youtube.com/watch?v=OuJBTDOL7RM) the cell and it will clear it. However, if it's a contaminant then it is more difficult.

I hope that helps for the future but it would be good to see the Chromeleon backup file as they can hold amazing amount of information for the sequence/run/method.

Good-luck!

[IC-man · Accepted solution]

Could have a particle inside detector.  Organic coating the electrodes.  The voltage can fluctuate as flow enters the cell.      Always back flush the detector.  Usually, the problem will also occur in the suppressor.