Peak splitting - guard column?

Hello,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.I have fitted 2 new guard columns following the instructions but see the same chromatography in both cases. 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.Any suggestions?Thanks!Separation conditions:BEH C18 2.1 x 50 mmVanguard BEH C18Mobile phase A: 0.05% TFA in waterMobile phase B: 0.03% TFA in ACNDiluent: MeOHStrong wash: ACNWeak Wash: MeOH: water (10:90)


  • Hello,

    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..

  • 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?


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