Chromatography Forum

We have recently seen a ghost peak in our chromatogram which turned out to be Acetaminophen related compound determined by PDA. This contamination is seen only in one particular instrument not in others

We have tried to wash the system along with column with hot water, pure methanol, 1% Nitric acid etc, we still could not get rid of the ghost peak. I wonder if there is any part in the system which we could replace or clean to get rid of the contamination or what do you suggest to clean up?

Thanks a lot!

Dear AZPharm,

PDA is not a test of identity. Does your ghost peak show up in your blanks, or just the sample runs? When you move your system components to other systems (e.g. mobile phases, column) does it still not show up on the other instruments?

Sincerely,
Keith

Hi Keith,

Thanks for the reply!

The ghost peak shows up in my blank solution, when we moved everything to other instrument, the peak is not showing up in the blank solution.

Dear AZPharm,

Is your system dedicated, or does it get switched around a lot? I had a similar situation once on a system that got changed around often. There were other symptoms, but it turned out that my pump seals were leaking. When I took the pump apart it had soap in it (from one of my ion-pairing reagents).

Sincerely,
Keith

Is the ghost peak retention time always the same? If so, sounds like something when the autosampler rotor valve switches through its paces.

I'd clean that out, maybe just replace the rotor seal.

Isocratic or gradient?

Instrument model?