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Second peak in HPLC run

Question asked by petrotex on Oct 7, 2020
Latest reply on Oct 7, 2020 by gabcaron

I have setup a 1260 system with heptane as carrier.  I always see a second peak come out even though it is a pure hydrocarbon.  If I inject isooctane the sharp main peak shows up at 4 min and always a smaller broad peak shows up at 8 min.  When I inject heptane as sample I don't see it (same as carrier eluent).  Changing flow, temp, inj volume don't help.  I am starting to believe that it is something in the ALS valving but need a little guidance.