Hello,
I am using an Agilent 7890B with HP-1MS column SN19091S-913E. Periodically (~25%), when installing a new column, i run into issue where components eluting >35minutes have severely reduced sensitivity. GC parameters at the bottom using splitless injection.
i.e, one standard will have component not detected, while a standard that is 2x concentrated will have area count 100. I am using multiple equipment and verify there is no problem in standard prep because the other equipment have normal sensitivity and linearity.
I have reviewed common problems and solutions here...
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1) Standard too cold/compounds precipitate.
- Unlikely to be cause because other equipment is operating fine at the exact same time using same standards. -Also, previous column installed on the now troublesome equipment showed normal sensitivity.
2) Componds are not properly vaporizing in the injection port.
-Removed glass wool from the liner and reinjected same standards. No improvement to sensitivity. Are there other ways to see if this is happening?
3) Column has contamination.
-Issue has been found multiple times when installing brand new column, probably not the root cause.
4) There is a cold sport somewhere.
-Not sure if changing column could introduce cold spot somewhere somehow.
5) High column bleed
-Not observed
6) Purge valve (split) time set too short.
-This would be a method problem. This method shows normal sensitivity on other equipment and has on this equipment before replacing column.
7) Missing insulation around injection port.
-Insulation present.
GC parameters below.
Injector temp: 300C
Detector (FID): 350C
Gas Flow: H2 40mL/min
Air 400 mL/min
Makeup (He): 20 mL/min
Constant Pressure: 20 PSI
60C start temperature for 1 min
10C/min to 300C
2.5C/min to 325C
325C hold for 20 mins.
I have just reinstalled the same column backwards with the outlet side now at the inlet, and cut off ~1foot of the inlet and installed at the outlet. I am reinjecting same standards to see if maybe problem was on inlet side of column.
Since this problem occurs regularly frequently when installing new columns, does anyone have advice what i could try for troubleshooting next?
Thank you in advance.
