Ghost Peak on a TCD of HP Series II

[nappingpenguin]

Carrier gas: Helium
Column: Carboxene 1006
Oven: 23 C
Inj; 230 C
Det: 230 C

Problem: I have been receiving a ghost peak every 10 mins or so that only occurs after the first sample of the day is introduced. it still shows up if I do a blank run in the middle of the day and it shows up pretty consistently, though sometimes the interval changes. I have tried changing my injector and detector settings with no success. Any advice you guys have would be great. I also admit that my experience with GCs is quite limited so if someone has a resource they recommend that covers alot of the more technical aspects of installing and maintaining pieces of a GC (ie how to check carrier gas flow and installing a detector) it would be greatly appreciated.

[Don Shelly]

It's possible that you have a contaminated carrier gas filter or contaminated carrier gas. The gas could be depositing a compound on the head of your column which elutes around 10 minutes. Some HP Series II GCs have built in carrier gas filters just inside the left panel. They look like pen-like metal cylinders with carrier gas coming in and then feeding to the injection port. Remove those filters if they are there.

[AICMM]

nappingpenguin,

First, I have to assume that you are shooting gas samples, probably looking for oxygen, nitrogen and what not. I would first be tempted to suggest water but at those temperatures, the water will take ages to come off. So my next comment is that your ghost peak is what ever you do not allow to come off in your first run showing up in subsequent runs. Could be CO, methane, CO2 or what ever. So try this. Run a run first thing in the day but bake the column out at 140C or so right afterward and then run another run under your usual conditions and see if the ghost peak shows up again.

Best regards,

AICMM

[nappingpenguin]

Perfect, I did some experimentation and realized that I was only seeing these peaks after I did some larger volume injections which makes me think that I was overloading the column. Thanks for the help.