My GC/MS is not reproducible

[thohry]

Hi all,

One of our GC/MS in the lab (Agilent 5975) recently is not reproducible. The same sample and same peak, if I run several times, it may apprears as 500000 cts, and can be one million after that. We have check the ALS, the syringe, replace the liner, clean the source, replace new fillament but it did not help. The tune report is good.
Could it be anything else ?
Thanks for any input.

Thorry

[James_Ball]

We have had similar problems before. Once it was the little catch on the autosampler that sets the injection volume, randomly it would slip and go to 2ul instead of 1ul. Another time it was the split vent line was clogged up, easy fix on that is just replace the copper line from the injection port back to the split vent trap, and change the trap. You might also need to clean the hole for the split vent in the injection port.

[thohry]

We have had similar problems before. Once it was the little catch on the autosampler that sets the injection volume, randomly it would slip and go to 2ul instead of 1ul. Another time it was the split vent line was clogged up, easy fix on that is just replace the copper line from the injection port back to the split vent trap, and change the trap. You might also need to clean the hole for the split vent in the injection port.

Thanks James.
I would check the trap and see.