GC-MS Autotune
Posted: Tue Nov 02, 2010 2:35 pm
We have an unusual situation going on with our Agilent 7890 / 5975C GC-MS system. Here is the problem...
For the past year when we do the autotune everything passes and comes out great but when we go to run our calibration standards it fails for linearity, 0.995. Now it just doesn't fail that once it will continute to fail for 3 days. Then miraculously on day 4 the calibration passes achieving a 0.998/0.999 and the instrument is stable for a few weeks. After those few weeks go by the response drops and we have to retune the instrument. And again 3-4 days go by where the responses for calibration are all over the place and we can not achieve linearity but on day 3 or 4 we are good to go.
The analytes being injected on this system is for phthalates - plasticizers.
This is what we have tried:
1. Called Agilent and have had them here numerous times. They are still trying to fix this.
2. The entire inlet has been swapped out with a new S/S one.
3. Prepared new calibration standards
4. Performed Leak checks
5. Cleaned the source many many times
6. Changed the type of inlet liner and septa.
7. We have tried hundreds of injections with the Agilent FID (n- tetra, penta, hexa decane in Hexane) standard and method (to rule out wether or not it may be our standards and method) and the response increases 30% from the initial injection directly after tuning in a 24 hour period.
8. Also there was a PM recently performed
After all of this the problem is still there.
Has anyone else out there ever seen this happen?
PLEASE HELP!
For the past year when we do the autotune everything passes and comes out great but when we go to run our calibration standards it fails for linearity, 0.995. Now it just doesn't fail that once it will continute to fail for 3 days. Then miraculously on day 4 the calibration passes achieving a 0.998/0.999 and the instrument is stable for a few weeks. After those few weeks go by the response drops and we have to retune the instrument. And again 3-4 days go by where the responses for calibration are all over the place and we can not achieve linearity but on day 3 or 4 we are good to go.
The analytes being injected on this system is for phthalates - plasticizers.
This is what we have tried:
1. Called Agilent and have had them here numerous times. They are still trying to fix this.
2. The entire inlet has been swapped out with a new S/S one.
3. Prepared new calibration standards
4. Performed Leak checks
5. Cleaned the source many many times
6. Changed the type of inlet liner and septa.
7. We have tried hundreds of injections with the Agilent FID (n- tetra, penta, hexa decane in Hexane) standard and method (to rule out wether or not it may be our standards and method) and the response increases 30% from the initial injection directly after tuning in a 24 hour period.
8. Also there was a PM recently performed
After all of this the problem is still there.
Has anyone else out there ever seen this happen?
PLEASE HELP!