I have an on-going bleed problem with a wax-type column.
I dont hve the problem with the other column in the oven. I have replaced liners and cleaned carrier lines and replaced charcoal traps.
I noticed today that when I shut off carrier flow at ambient temperature my FID signal increases from 0.97mV to 1.30mV over a 2min period (at low sensitivity). When I resume flow and oven is at 70degC the signal goes down to 0.97mV.
Anybody have an explanation?
I would use a good column in place but I fear contaminating it!
By Anonymous on Thursday, February 19, 2004 - 11:02 am:
This does not sound like column bleed. If there is no flow through the column, then how could column material be carried to the detector?
By Anonymous on Friday, February 20, 2004 - 07:28 am:
You are changing the dynamics of the system. If you shut off the column flow you are changing the flame conditions and it is not unreasonable to expect a baseline change, especially if you are running a high column flow. I don't see how this is a bleed problem. The classical bleed problem is a large increase in baseline with increased temperature.