Has anyone been having issues with InfinityLab Poroshell 120 EC-C18 colummns (PN 695975-302)?

Has anyone been having issues with the InfinityLab Poroshell 120 EC-C18 columns (PN 696975-302)?  We ordered one, and tried our daily check solution on it but the results did not look like what we normally see.  We also observed that the starting column pressure was lower (165 bar), and went really low (25 bar) as the gradient switched to more organic mobile phase.   We asked for and received a replacement column, and that one worked as expected for about 3 weeks.  Today we saw the same  problem with the daily check.  We checked for leaks, but did not find any.  We have the same column on another instrument that has been functioning normally for months now.  Has anyone else been having issues with these columns?  Any ideas what could be causing this?  Thanks in advance.

  • Have you tried that same column on the other system that is working?

    This is the first I have heard of low pressure issues.  The fact that you have issues with two columns on the same system makes me think there’s something going on with this HPLC. .  

     

    Also, what is the pH?   If the pH is too high it can dissolve silica – all silica, doesn’t matter who makes it.  Some bonded phases, like our HPH, include a coating to protect the silica but most columns have silica that dissolves around pH 8 – 9.  It’s also important to remember that pH of an organic is a misnomer.  Typically, organics behave as if the [OH]- concentration is much higher than the “pH” the customer thinks they have. So, if you are buffering ACN to a pH of 4, I wouldn’t worry about it but if it's a pH of 8 (right at the upper range for a column) then this could be chewing up silica.  One of the biggest mistakes I regularly see (hear about) from customers is not flushing columns after use and/or not counting the time that a column is “not in use” but sitting in harsh mobile phase conditions.   Of course,  I also realize that if the silica were actually dissolving, you would see poor peak shape – peaks split at the apex when a void is created.

     

    Ultimately, if you are seeing low pressure but  are not seeing signs of a void forming in the column – either from silica leaking out or dissolving – then I would look at the pump rather than the column.  For example, when the pressure is low,  replace the column with a restriction capillary and run the leak rate test or the system pressure test.  If you aggressively purge the system with IPA prior to running these tests and the tests pass,  immediately install the column and run IPA through it to check pressure.  Remember to start the IPA through the column at a low flow rate since it is viscous and the pressure is expected to be higher.

  • My apologies for the long delay (things were busy here, then all hell broke loose in the world).  We are using water and acetonitrile for the mobile phases buffered with formic acid (0.1% v/v).  I spoke with an Agilent engineer on the phone, and he thought there may be air bubbles in the lines.  I visually inspected them but did not see any.  Nonetheless, I re-primed the lines, and flushed out the pump head.  The problem still persisted. We back flushed the column at low flow for several hours, and noticed an improvement.  We back flushed again overnight, and this seemed to do the trick.  We ran our daily check solution and things appeared normal, all peaks showing at the appropriate retention times.  The pressure was a wee bit lower than before, but everything appeared to be fine.  I was wondering if maybe there was some air bubbles or some kind of contamination (bacterial?) in the column.  We will keep your advice in mind if this problem crops up again.  Thanks for the help!

  • Oh, forgot the first thing you inquired about.  I tried the column on two different instruments - same result.   After trying this, figured the pumps were OK. 

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