Deactivated silica in transfer line

[Jasn]

Hello all,

i'm thinking about putting a piece of deactivated silica in the transfer line (and couple it to my analytical column) instead of the end of the analytical column itself. The system is used to analyze PAH's and transfer line is held at 300°C-320°C to minimize PAH tailing.

The reason i want to do this is because I think that then:
1) the column itself is exposed to lower temperatures overall and should show less degradation (peaks of higher boiling PAHs start to tail after a while and trimming the transfer line piece helps)
2) I could actually use a lower transfer line temperature, since deactivated silica is far less retentive (analytes migrate at 150°C less than they would do from a coated column)
3) Replacing the piece in the transfer line is cheaper and would not impact the chromatography, since the analytical column does not have to be trimmed.

Are my assumptions correct? If so, which consideration should I take when choosing diameter, length etc... for the deactivated tubing.
The analytical column I use is a Select PAH 15m*0.15mm*0.1µm from Agilent. I'm thinking about 0.5m of 0.15mm or 0.12mm i.d. tubing.

Thanks in advance for the input!

Kind regards,

Jasn

[Peter Apps]

Presuming that this is the transfer line form GC to MS (and not from a sampler to an inlet for e.g.) then it might work. With such a short narrow column any tiny dead volume in the connector will significantly degrade the separation.

Peter

[Jasn]

Peter,

Thanks for the info. It is indeed the transfer line from the GC to the MS. I know that any dead volume could degrade the chromatography significantly.

Any considerations regarding dimensions of the silica tubing to use?


Jasn

[Peter Apps]

Peter,

Thanks for the info. It is indeed the transfer line from the GC to the MS. I know that any dead volume could degrade the chromatography significantly.

Any considerations regarding dimensions of the silica tubing to use?


Jasn

I don't see any reason not to use the same dimensions as the column - just add the extra length to the column in the GC setup and the software will deal with the flows and pressures.

Peter