Chromatography Forum

hi i am getting a ghost peak after the peak of interest have tried new prep brand new column and cleaned up the hplc system with nitric acid the peak doesnt change size or retention time at all what should i do i have been performing the test in years with no problem

Isocratic or gradient?
And does the peak show up in blanks or in samples only?

It is an isocratic method and it only shows up in the sample injections the column is a polysep GFC 1000 and mobile phase 10% methanol in water.

If you're not already doing so, try dissolving your sample in the mobile phase and see if the peak goes away. If it persists, then it's possibly real, or due to some sample degradation. From the column, I surmise that it's a size exclusion separation, which would mean that the ghost is a smaller molecule than the main peak (or else that there is some secondary interaction going on).

Is your blank taken through all the same sample preparation steps as the sample?

e.g. pipetting, filtering, centrifuging, etc? Changes in the quality of your sample prep consumables could be the cause