Can I use a 100% aqueous mobile phase with my LC column?

You might be asking this because you have read that not all columns are OK to use with highly aqueous content (>95%) in the mobile phase.  Or maybe the caption caught your eye because you have recently encountered some difficulty with using highly aqueous mobile phase.

There is a phenomenon called “phase dewetting” that can occur with LC phases that are composed of the longer alkyl chains such as C18 and C8.  Phase dewetting results in a sudden and dramatic loss of retention, as well as poor peak shape. If you would like to read more about phase dewetting, I suggest reading the following:

A C18 is a C18, right?

More Technical Service "Red Flags" - LC

http://www.chromatographyonline.com/lcgc-blog-chromatography-technical-tips-polar-analyte-retention-and-phase-collapse

http://files.pharmtech.com/alfresco_images/pharma/2014/08/22/55290841-3e3e-433b-a5d4-adb7f6495a06/article-32973.pdf

http://www.waters.com/webassets/cms/promotion/docs/Polar-Retention-Reversed-Phase-LC-Webinar-%20Pres-Kevin-Jenkins-Oct2016.pdf

 

As mentioned in one of the above listed blog posts, “A C18 is a C18, right?, our “Aqueous C18” phases are quite different from conventional C18 phases.  This includes our Ultra Aqueous C18 and Pinnace DB Aqueous C18 phases.  We also have a few other phases that can be used with up to 100% aqueous mobile phase. You might notice from reading the referenced articles that pore size and bonding density has some impact also. Here is an all- inclusive list of Restek LC column phases that will tolerate 100% aqueous conditions:

Ultra Aqueous C18

Ultra IBD

Ultra Biphenyl

Ultra PFP Propyl

Ultra Aromax

Ultra Cyano

Ultra C1

Pinnacle DB Aqueous C18

Pinnacle DB IBD

Pinnacle DB Biphenyl

Pinnacle DB PFP Propyl

Pinnacle DB Cyano

Viva C4

Viva Biphenyl

Viva PFP Propyl

ROC Phenyl-Hexyl

Roc Cyano

Raptor Biphenyl

Raptor EtG/EtS

Raptor Fluorophenyl

Force Fluorophenyl

Force Biphenyl

Please note that although the above phases are known to be aqueous tolerant, we may not have generated data (chromatograms or application notes) at >95% water content in the mobile phase. This is simply because we have not performed the application and, most likely, there has not been much demand for using a high aqueous mobile phase for applications that are commonly run on that column phase.  If you do have any questions about whether or not your column is suitable for an application, please feel free to contact us in Tech Service.

I hope you found this post helpful.