I have GC-FID 8890 and there's problem is suddenly appeared, the increasing shift in retention time for concentrated samples and for some of diluted samples that I previously injected and the retention time didn't have any shift.
Please consider, I don't change any parameters of the method such as flow gas or temperature.
I did some procedures but the problem is still persist :
1- I replaced septum
2- I perform inlet and septum leak test and obtained pass the tests