Do you have the method parameters for the injection and inlet?
They maybe incompatable with one another, for example, a large injection volume followed by a high split on a pulsed pressure injection followed by a large jump in inlet purge flow maybe going from one extreme value to another, pushing the inlet limits.
Can your inlet reach 60 PSI? - if not then there is a leak on that inlet.
How long is the column into the inlet? - check with length fits the tolerances, this may contribute to the peak change
Does the fronting an reproducability get worse with more injections, one after another then later on in the day it's "reset"?
This is a manual injection on a split, single taper, glass wool, deactivated, low pressure drop liner using a 70 mm manual injection needle where I inject 0.5 ul of sample. The inlet parameters are below:
Pressure: 4.94 psi (On)
Split ratio: 50:1
Split flow: 49.9 mL/min
Total flow: 53.4 mL/min
Gas saver: On
Saver flow: 20.0 mL/min
Saver time: 2.00 min
Gas type: Nitrogen
I performed leak tests and didn't see any evidence of a leak. The column is installed 5 mm past the ferrule into the inlet as described by manuals. The fronting gets worse with more injections - sometimes I don't see any fronting at all until multiple injections, and then the next day again there is no fronting until multiple injections. At the same time the area of the peaks decrease with multiple injections and the ratio of peak areas are not consistent (no pattern, just all over the place)
I think we need to see the method parameters. The 0.2 valve switch is short, that may be to compensate for vapour volume. Water in your sample, depending on percentage can be very difficult to contain inside the liner as it has vapour volume that can easily expand beyound the liner and cause carryover and other issues. The method parameters as a whole may give us a better picture.
I added some method parameters above. The valve switches on at 0.2 and off at 0.5. What do you recommend for the valve switch. Right now I'm having the reproducibility issues with the sample that doesn't contain any water.
I am not sure if this is still an issue, the valve switch seems short, usually suggest 0.5 minutes or more . Feel free to post again is there is still an issue. I will mark assumed answered for now.