Trouble with upper and lower limits of linearity on a GC

[MX304]

I am having issues with some re-validations on some of our older instruments. I have five GC/MSs that are being used to test for drugs of abuse (THC specifically) Two are 6890 / 5975 combos and three are 6890 / 5973 combos. All are running the same Chemstation revision. On the 5973s I can get the required response at the upper limit of linearity but not the lower limit, or I can make some adjustments and have the needed response at the lower end, but not the high end. The 5975s run the same samples just fine. We have eliminated all of the easy fixes and are rather stumped at this point. Any thoughts?

[danjstemarie]

Have you tried using the larger diameter drawout plate on the source? This was introduced to help with linearity issues that some 5973s were having.

[MX304]

Have you tried using the larger diameter drawout plate on the source? This was introduced to help with linearity issues that some 5973s were having.

I didn't know such a thing existed. I'll check into it.