HPLC Troubleshooting question

Jim Napier napierj at agresearch.cri.nz
Thu Jul 27 08:31:37 EST 1995


In article <11EF24B23F5 at botany.uq.edu.au> J.Marcus at botany.uq.edu.au ("Marcus, Dr J.") writes:
>From: J.Marcus at botany.uq.edu.au ("Marcus, Dr J.")
>Subject: HPLC Troubleshooting question
>Date: 25 Jul 1995 16:16:31 -0700

>Dear Netters,
>     I have been struggling with our Waters HPLC
>for over a month now and would appreciate ANY clues 
>that might help sort out the problem.  If there is any 
>interest, I will post a summary of responses.
>     The problem manifests itself as an extremely wavy 
>baseline which coincides with the pump cycle of pump B 
>(6000A Series pump with dual piston design).  After 
>changing the pump seals and check valves, the problem 
>remains.  Every indication now seems to point to a bubble in 
>one of the pump heads; but, try as I may, I have not been 
>able to get rid of it.  I have tried pumping methanol; I 
>have used the solvent draw-off valve to pressurize the 
>intake line while the pump is going at 10ml/min; I have 
>tried tapping the pump head.  
>     Has anybody else encountered this problem? 
>     ANY tips that might be useful in getting the bubble out of 
>the pump?
>     Could anything else explain the wavy baseline (e.g. warn out 
>cams driving the pump heads, or a particle in the pumping 
>chamber)? 
>     Would any particular cleaning procedure help?  

>I will be MOST grateful for any assistance.  

>Sincerely,
>John Marcus




>_________________________________________________________
>John Marcus            Marcus at tpp.uq.oz.au (Dr J.Marcus)
>Cooperative Research Centre for Tropical Plant Pathology
>5th Level John Hines Building
>University of Queensland
>St. Lucia, QLD 4072
>AUSTRALIA
>Fax: 61-7-365-4771
>Phone: 61-7-365-4764

I have one suggestion, which I have found usually works if the problem is 
caused by a bubble in the pump head, but it does take a little time.  Judging 
from the fact that it has been on-going for a month, I guess a couple of days 
is not long (if it works).  

Try using highly degassed solutions, and any air bubbles in the 
pump head should eventually dissolve.  You will want to be degassing at 
regular intervals to ensure that the solution has the maximal capacity to 
take up gas, and so an on-line helium or nitrogen sparging system would be 
better than vacuum degassing, which often leads to new bubbles being 
introduced into the line when it put back into the reservoir.  I know this is 
not particularly high-tech, but it has worked for me over the years.  Good 
luck and let's hope you're up and running before too long.

Jim Napier
 




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