I am working with a 7820A GC and 5977B MS. Recently, we changed the helium tank and since then we have been seeing baseline noise in the chromatogram which is high enough to interfere with my peaks. We also found that the N2 and O2 counts have been higher than we used to see; 5-8% and 1-1.8% respectively. Previously, the counts used to be 1-2% and
Proper troubleshooting is a must. Refer to troubleshooting guide for the same.
Higher N2 rates indicate that there must be a leak. Try to find out using a leak detector. Also, check the column nuts and connection points. After lots of injections which cause temperature cycles can loosen the connections. Also, change the gold seal (inlet seal) if possible. But as I mentioned if you are observing it only after changing the cylinder then it should come from cylinder connection as Dr.Noel W Davies indicated.
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