Chromatography Forum

Dear all,
I am having real trobles with a method for detection of Volatile fatty acids in the GC (solvent is water). I generally get very nice peaks with good separation and good simmetry. Nevertheless, at random injections, the peaks appear with really wierd shapes. The question is that when this happens, if you inject from the same vial again, the peaks are ok again.
It is completely random. I would attach an image but I can not.
I have to say as well that the same GC is used for another purpose (with the same column) using organic solvents and that we never observed that.

Anyone has an idea of what can be wrong? Any idea of what can cause interferences in a random way?

Many thanks in advance.

Anna

Hi Anna,

Previously, we have the same issue that random ghost peak was observed and the peak area of target analyte was unstable. After PM, it was found that the gold seal in the inlet and other parts were contaminated. Therefore, we replaced the jet, gold seal, split-vent trap and split line. After that, everything goes bakc to normal. This may be one of the root cause you can assess. Thanks.

sisay

Hi Anna

Welcome to the forum.

It sounds as if you have peak distortion, not ghost peaks, which are peaks that elute in a run after the run they were injected.

Instructions for posting images are in a sticky on the LC page, and we need all your operating details; temperatures, flows, volumes etc etc if anyone is to do anything more than guess what the problem is.

Peter