I have been experiencing some trouble with my linearity on my siloxane method for air samples. Right now about half my analytes are either not linear or tailing off.

The instruments that I use for the autosampler/preconcentrator are Entechs system: 7650 and 7200 (a cryogen system). The sample then goes into a GCMS to be analyzed.

A few things that I have tinkered with already are as follows:
    Checking for leaks on both systems (leak free)
    Ensuring that the flow of the sample is at 100%
    Increased some bake temperatures on the 7200 preconcentrator
    Changed from running in a tedlar bag to a canister.

Some of the analytes even as the injection volume is increased actually decreases in response.

Other analytes are linear in comparison to the ones that are not. I have attached images for reference to one of the analytes causing problems.

Images: https://postimg.cc/gallery/g3BpV2d