My knowledge of GC is definitely very limited compared to other types of chromatography, so I am going to come to the experts.

Situation: I have a formulation that I am analyzing via GC-FID. The active has a concentration of 0.75% and the solvent is a combination of PEG 400/Polycarbonate.

My current method parameters are as follows:

Column: 30mx0.25(i.d.)mm DB-1701. film thickness is 0.25um, 14% cyanopropylphenyl 86% dimethyl polysiloxane.

Split injection
Split flow: 100ml/min
1ul injection volume
Oven: 245C constant
Injection and detector 270C
Helium gas at constant velocity of 35cm/s

I have no problem resolving my main peak of interest from any solvent peaks. BUT because my nominal active is so small, I'm using about 13g of formulation in a 100mL volumetric flask to ensure my active peak has a signal comparable to the bracket standards. The problem is that the TPP is expected to elute around 10-11 minutes...well it just so happens that it seems as though PEG 400 also elutes around 10-11 minutes. Because I have such a large amount of solvent, my PEG 400 peak is rather large.

Ideally I would like to NOT change either the column or the sample preparation. I would only prefer to change system parameters. So, if anyone has any suggestions in separating a rather large PEG 400 peak from TPP, I am all ears!

I will get a few chromatograms together and update this thread, or reply to it with some chromatograms for reference...after I read on how to do so.