pressure problems making no sense

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

9 posts Page 1 of 1
I recently changed my column filter. After doing so there have been odd issues with the pressure. Currently I am experiencing the BAR reach 160 and stabilizing for several minutes. Once I start the run, the first sample stays around the same BAR but then the next samples start to loose pressure. The pressure starts to drop to to 155, then 150 and so on. By about 5 runs in, the BAR is at 147-148. Today it is going from 151 to 156 during the run, where as usually it just stays around the original BAR it started at.

All of this is odd, starting with my beginning pressure. Normal BAR is 153. Since I changed the column filter I have experienced leaks and pressure fluctuation. I have replaced the filter several times before with no issue. I feel like once I replaced the filter this time around, then trouble shot after the pressure was acting funky, I caused a leak. Then I fixed this leak but feel like I may have tightened something too much. I really can't put my finger on it as usually, when there is a leak, the pressure drops. When there is a clog, the pressure rises. Sometimes I can see the pressure moving up and down with the rhythm of the pump. None of this is the case right now. There are no air bubbles that I can see and no Failures happening. Please help.
Hi SergioM420,

By column filter, do you mean the in-line filter upstream of the column?

It may be that the connections to the six-way valve may require detaching, reseating and tightening as the trouble is happening during injections. Just an idea. Carefully check all connections for microleaks--it is true that overtightening fittings may cause leaking.



Best Wishes!
MattM
Thank you for your response. The pressure is happening throughout the run, varying from one to the next. One run will maintain at 156-17 and then the next 151-152. Is that an indication of the 6port needing re-seating and tightening?
I opened the six port injector valve. I feel like your suspicion was correct. There is a black seal that has a spring lining it, which has significant damage to it. I believe it is possibly the injector valve rotor seal. It is between the rotor seal and stator face assembly, inside of the stator ring. Do you know which part I speak of? Any help appreciated.
Hello Again,

Doesn't sound familiar--which make/model of HPLC instrument are you using? Maybe i can find a diagram of the injection valve.
MattM
Ah that is better, just needed a bit of a refresher. could be either a wash seal (most likely) or a plunger seal. Other than this seal looking damaged, is there evidence of a leak?
MattM
mattmullaney wrote:
Ah that is better, just needed a bit of a refresher. could be either a wash seal (most likely) or a plunger seal. Other than this seal looking damaged, is there evidence of a leak?



It was an isolation seal. I replaced it. It seemed to help for a bit. Matt I would love to contact you via mobile or something you trust. I would appreciate some over the phone help. If not, could you tell me whats the best way to become fluent in chromatography and HPLC instruments. I just want to learn more and be able to work on these instead of needing a technician which I have been able to do so far. I have only been in this field for a year and have basically been tackling problems on my own with online help from pdf manuals and youtube videos. I have learned how to do a number of things but need some support. We are a state certified lab in New Mexico trying to do big things with little help. Email me if you want to trade contact info. sergiomuterperl@gmail.com Thanks for your help thus far!
Good Morning,

Seems to me you're off to a good start. I do not claim to know every single aspect of troubleshooting, I've become better at recognizing some of the more common problems over time. I've read my share of pdf files and watched YouTube videos--particularly those from Agilent and Waters. Learning does not cease, there is always something else to know.

The best thing you can do--if you're persuasive and fortunate--is to complete LC vendors' courses (not easy these days to get funding/permission, I know that). I've been fortunate in my past with regard to this kind of thing.

Here are two useful websites to bookmark:

http://www.lcresources.com/training/tsbible.html

https://www.lcresources.com/lcr/lc-trou ... ing-bible/

This book:

Troubleshooting LC Systems: A Comprehensive Approach to Troubleshooting LC Equipment and Separations (1989 Springer-Verlag, ISBN 9780896031517) by John W. Dolan and Lloyd R. Snyder, is a good book to find for on-your-own
learning. In part, you learn how to approach troubleshooting through reading--it's pretty effective, I think.
MattM
mattmullaney wrote:
Good Morning,

Glad to have helped a bit. 8)

Seems to me you're off to a good start. I do not claim to know every single aspect of troubleshooting, I've become better at recognizing some of the more common problems over time. I've read my share of pdf files and watched YouTube videos--particularly those from Agilent and Waters. Learning does not cease, there is always something else to know.

The best thing you can do--if you're persuasive and fortunate--is to complete LC vendors' courses (not easy these days to get funding/permission, I know that). I've been fortunate in my past with regard to this kind of thing.

Here are two useful websites to bookmark:

http://www.lcresources.com/training/tsbible.html

https://www.lcresources.com/lcr/lc-trou ... ing-bible/

This book:

Troubleshooting LC Systems: A Comprehensive Approach to Troubleshooting LC Equipment and Separations (1989 Springer-Verlag, ISBN 9780896031517) by John W. Dolan and Lloyd R. Snyder, is a good book to find for on-your-own
learning. In part, you learn how to approach troubleshooting through reading--it's pretty effective, I think.
MattM
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