Hi All,

I have an issue with my NGA GC. I run my cal gas with a fixed flow rate and somehow the retention time for channels B and C was shifted on every injection.
Can someone advise what I need to do? In another issue, I noticed that there were toluene and hydrocarbon heavy end peaks on the chromatogram. however, when I injected the Air Blank, the toluene peak is not there. the line is clean by acetone and treated by 60 deg heat overnight and the issue still persists.

please help me.