Two columns in series??

Discussions about GC and other "gas phase" separation techniques.

3 posts Page 1 of 1
Hello there!

I have received a shiny new Agilent 7000D (Agilent 8890 GC with 7000D MSD) which I am in the process of getting to grips with. I was expecting it to be delivered with a 30m HP5ms column, but instead, it was delivered set up with a 15m HP5ms type column which is joined through some kind of union (itself connected to gas supply perhaps via a secondary EPC?) to a second 15m HP5ms column which then joins into the MSD as normal.

This isn’t exactly a setup with which I am familiar and I would be much obliged for some advice as to whether this setup can provide equivalence to a single 30m column and if so how I can achieve this? Is it as simple as setting the flow rates for both columns to the same value (i.e. 1.4ml/min) or is it more complicated?

Beyond the ability to do concurrent backflush (and all that fancy stuff) are there any additional benefits of this kind of setup? I’m guessing that the first column probably takes the brunt of any fouling etc. so perhaps it might allow changing of just column 1 when the inevitable happens and resolution is lost (and I guess a 15m column is cheaper than 30m) or is that wishful thinking!?

Many Thanks

Richard
Probably it is the Dean's switch.
Pressure removed from the head of first column and applied to the EPC inside T-connector makes the following:
* First column flushed in reverse direction
* Second column works as usual and separates what have already trapped there.
* Without backflush that construction works as generic 30 m column
* While EPC active - the 1st column can be easily disconnected and changed without the vacuum loss and MSD remains on-line.
Thanks for taking the time to respond and for the confirmation. :)

R
3 posts Page 1 of 1

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