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Hi there,

I'm looking for a capillary column for the analysis of traces of ethanol and cyclohexane in water.
I need your help . What is the best column ? I hesitate between a column as a DB5 or a column more specific as DB624.
what do you think about it ?

thanks in advance

Hello,

I think DB-624 is a good choice, but can also be done on a non-polar column as DB-1 or -5.

Actually, I am a little bit confused and surprised that on a DB624 we can inject aqueous solution ( water ).
Maybe I should rather use a polar column like DBWAX (with a intern diameter 0.53mm and a film thickness of 2 or 3µm ) ? and install a guard column ?

What do you think about it ?

To my mind, both columns DB-624 or DB-Wax will work even with direct water injection.
The main problem is the big water vapour cloud in the injection port (it seems to me that headspace method would be better) which can cause some trouble, but the column is OK.
If you have non-volatile compounds (like salts) in the water that may damage the after some injections and a guard column is highly recommended, in this case.
And if this is the case headspace is really the best method to use.

To let you know, these columns should not be used for direct water injections:
Only non-crosslinked stat. phases like Carbowax 20m, CAM and HP-20M should not be used with direct water injection, because the stat. phase may get washed off.
All other stat. phases are safe, as long no salts, mineral acids/base are dissolved in the water.

Good luck with you ethanol and cyclohexane