Water Injections - Polar or Non-Polar Column?

Chromatography Forum: GC Archives: Water Injections - Polar or Non-Polar Column?
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Tuesday, April 1, 2003 - 09:49 am:

For doing analysis of water solutions, is it recommended to use a polar or a non-polar column if either is a viable option? Which is better suited for repeated water injections?

Iím currently analyzing 1 microliter injections containing 1-10ppm Ethylene Oxide, Ethylene Chlorohydrin, and Ethylene Glycol in Water. Iíve tried it both with a Non-Polar Dimethyl Polysiloxane column (5 micron thick) and Polar Polyethylene Glycol columns (0.5 and 1 micron thick).

Since my analytes of interest are polar the polar column seems like a better choice but I know that water on a polar column can pose problems with column degradation. However, putting water onto a non-polar column seems like the water could bead up and affect the detection of analytes or possibly put the FID flame out. My main goals are to be able to see down to 1ppm and to minimize peak tailing.

Any feedback would be very much appreciated.

Thanks.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Tuesday, April 1, 2003 - 11:22 am:

We use 0.5ul injections for water solutions, due to such large coefficient of expansion over-loading capacity of split liners. And we use polar capillaries for those injections (Supelco Nukol). Matter of fact, I'll be doing one such sequence this afternoon.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Rod on Tuesday, April 1, 2003 - 08:06 pm:

Based on my experience with process control and lab applications the possibility of degradation is minimized if the water is kept vaporized and not allowed to condense on-column.

I believe the PEG column is a better choice for a longer lifetime.

I would be concerned with your injection liner increasing in activity with time. Be sure you clean and deactivate or replace the liner regularly.

Be certain you have enough expansion volume in your liner to deal with 1ĶL injections so you do not deposit your analytes in colder upstream areas of your injector.

Rod


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Ralph Calvert on Wednesday, April 2, 2003 - 02:12 am:

You will find this item on the Agilent website useful.

http://www.chem.agilent.com/cag/cabu/pdf/b0331.pdf

Essentially it says that it doesn't matter which column, most problems are due to flashback. So, as previously pointed out keep the inj temp reasonably low(150-200) and use a wide bore liner. 1ul water expands to about 1000ul. I use 1ul splitless injections on a polar column with no problems.
see also
http://www.chem.agilent.com/temp/rad27D80/00028972.pdf

hope that helps

Ralph


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