Peak splitting - guard column?

<p>Hello,</p><p></p><p>I am seeing peak splitting when using a Vanguard column but not when it is removed (see attached example). It seems likely to be due to dead volume in the fitting.</p><p>I have fitted 2 new guard columns following the instructions but see the same chromatography in both cases. </p><p>The fittings look ok on the guard column once tightened, the length of tubing exposed looks the same as the other fittings on the system.</p><p></p><p>Any suggestions?</p><p></p><p>Thanks!</p><p></p><p>Separation conditions:</p><p>BEH C18 2.1 x 50 mm</p><p>Vanguard BEH C18</p><p>Mobile phase A: 0.05% TFA in water</p><p>Mobile phase B: 0.03% TFA in ACN</p><p>Diluent: MeOH</p><p>Strong wash: ACN</p><p>Weak Wash: MeOH: water (10:90)</p>


  • dougm


    Have you ever achieved success with any VanGuard column(s)? Or, is this a recent occurrence?

    Have you tried replacing the tubing that goes into the VanGuard Pre-Column? Perhaps there is an improperly formed fitting at the inlet of the VanGuard pre-column (vs. your troubleshooting efforts that have focused on the outlet fitting that connects the VanGuard pre-column to the UPLC column)?



  • Hi Doug,

    We have sucessfully used Vanguard columns before.

    I have also tried replacing all of the fittings before and after the column and guard column but with no luck.



  • may be changing the main column/guard column  frits could help..not sure though..

    Atleast, in my case column life time increased dramatically by changing  inlet column frits..

  • RD

    Have you considered the possibility that the Vanguard is adding a little more resolving power and that the peaks are real ?

    It seems to me that the data doesn't present as classic peak splitting.

    I wonder what the separation would look like using a 100 mm column.

    Have you tried this ?



  • Hello,

    As I look at the data I sort of agree with Rich. It does not look like classical peak splitting to me either.

    What WOULD this separation look like on a longer column?