I am working with Agilent HPLC 1100. For the last few days, it started to show a rapid increase in back pressure whenever I flushed it with water (ultrapure, deionized, not buffered) up to 400 bar, where it shuts down. Whenever I use methanol or acetonitrile, the back pressure goes to its normal level (10-15 without the column). Any suggestions about the cause and how to avoid/solve this high back pressure problem?
Are you using the same pump/channel for the water as you are for the methanol/acetonitrile? If not, then perhaps you have an issue with only the aqueous pump (probably the A pump?). Check valves might be the problem. Try running methanol through all of the channels and confirm the flow rate with each pump individually.
Water is also more viscous than the organic solvents so both lines might still have a problem (I am not sure if it is that much more viscous though...). On our Agilent 1200, back pressure with no column could usually be traced back to a really dirty filter in the purge valve, which turned out to be the filter that we needed to change out most often even though we filtered our solvents daily. To fix it we un-screwed the valve knob and replaced the tiny filter inside it (about the size of your pinkie tip). This just became part of the monthly or so maintenance that we did, in addition to filtering the solvents daily.
Thank you very much Wade A Rourke and Terence Spencer Crofts for your valuable suggestions. I will try all the possibilities you have mentioned. Good day
Terence Spencer Crofts, thank you so much for taking the time to provide your answer, and Usama Alshana, thank you for asking the question. I was observing the same symptoms and your lucid explanations of both the problem and the answer helped me find the solution far more quickly than I would have otherwise! Replacing the "purge valve frit", P/N 01018-22707, per the instructions in the Maintenance section of the quat pump user manual, did the trick for me!
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