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- Posts: 52
- Joined: Fri Sep 30, 2011 2:24 pm
I set up a new instrument with new column using same instrument method yesterday. I set up original instrument but modified instrument method to be “constant flow” as i noted in software "constant pressure" was selected. . New syringes and inlet liners were installed on both instruments. Both systems observed the exact same retention time shift at the same time this Friday morning. It is almost as if a different carrier gas is getting pumped in when this occurs. . An air blank was running on one instrument the same time a standard injection was running on the other instrument. the air blank showed a notable rise in the baseline. the standard injection showed the sharp change in retention time and increased peak areas. the next several injections were unchanged with both systems showing 3 mins retention time and massive peak areas. At the same time on both instruments, the retention time jumps back to 4 minutes and more expected peak areas are observed. This coincided with the delivery from BOC and the full Helium cylinders being hooked up to the manifolds. So despite my assay/instrument not requiring helium, if helium is not hooked up out in the compound area, my retention time will shift to 3 minutes/peak areas will increase. In total this has happened 4 times in as many runs and this has not been observed any other week across familiarization runs/robustness/specificity/precision runs and appears to coincide with when the Helium line on the neighbouring manifold is fitted with new full cylinders/Helium cylinders empty. I am not sure what the issue is but I will hold off on setting up my last two validation runs until after all lines are filled with all gases out in the compound.
Any feedback would be appreciated.
Thanks
Eoin