Chromatography Forum

Hi! We have a new GC2030 from Shimadzu. This is the 5th instrument of this kind that we have so it is not new to us. We run wastewater treatment samples on it that have been lowered to 2-3pH. We are testing for MeOH, MeAc, Benzene, Toluene, NBA, BOH, and HAc. My issue is with HAc. All of the other components come in the standard range, and areas remain consistent. With HAc, the area seems to go out of control the more samples that are run in sequence. The liner, septum and syringe have been changed, I have conditioned the column. There is no carryover for any other peaks. The area will start out around 500,000, and after 4-5 runs, it will have worked it's way up to 2.5million, all while running the same sample repeatedly. Should my next step be to trim the column length? I guess I'm confused as to why it is only HAc.
Thanks for any input!

Helpful are details about the method conditions. Is there a equilibration time at the end of the run? I read not having one can result in strange things which only appear in sequence runs. I would be curious enough to attempt single runs with progressively longer time between runs just to see what happens. I would also troubleshoot using a standard made with only HAc. Does this increase still happen. Does running a blank between runs in the sequence fix it?

What method are you using, and under what conditions?