Permanent Gases, PLOT Columns

[nerd75]

Greetings
Is anyone out there separating permanent gases with PLOT columns? What kind of lower detection limits can you get to?
I am specifically using Varian's dual Select Permanent Gases / CO2 (MolSiv5A PLOT + PorabondQ PLOT) but am not happy with O2 sensitivity. Can anyone recomend a better set of columns, or offer advice how to get down to low ppb levels here?
Many thanks-

PS I have eliminated the possibility of an O2 leak in my system. O2 seems to be physisorbing to my columns at these very low levels, losing sensitivity.

[chromatographer1]

Your results are reasonable.

What do you mean when you say low ppb levels ?

1, 10, 100 ppb? How LOW do you need to GO ?

Depending upon detector used you may have to condition the analysis by injecting an amount of oxygen between analyses at some rate.

Micropacked columns with fused silica coated SS tubes may be necessary due to the larger amount of sample that can be injected, of course, conditioning spikes may still be necessary.

best wishes,

Rod