Fluctuating RT shifts - purged/packed inlet GC

[Rhodium]

Experiencing an issue where RT's have been shifting (>5 shifts)...RT of one injection may be 5 minutes and the next 9, then 6, and so on. Seeing this issue across methods. This is on a purged packed inlet and also have noticed the pressure actuals are higher than the pressure setpoint. Any other ideas that would cause this issue aside from EPC or malfunctioning oven (run is isothermal). Any thoughts/suggestions appreciated.

[tkubowicz]

Hello

I'd recommend to do leak test for PP inlet to see if there is any leak.
I would also check inlet consumables/parts (perhaps replace): septa, liner, viton o-ring and 1/4" Vespel(graphite/vespel) ferrule.

Regards

Tomasz Kubowicz

[Rhodium]

Thanks, yep - the PP inlet nut was a tad loose and found a pretty good leak there. Upon inspection O-ring looked ok and after tightening the nut the flow actuals and setpoints now agree.