Chromatography Forum

Hi,

I am using Schimatzu 2010 GC to analysis for ethanol, colunm is agilent db-624 capillary colunm. injectoin volume is 1 uL. ı am trying initial temp of 40c and then up to 200c ramping. Ethanol peak is at approximately 4.5 min and it is tailing 3.5.
what can be reason and what can i do fix it?

Aha !! Sounds like USP <611> for alcohol, on 624 column. Unfortunately, 624 columns are not great for ethanol, we also get tailing, just not as good a column as are PEG capillaries. But it's the USP, and whoever developed the procedure likely had a 624 column around, or maybe already installed in his GC. And maybe same person for USP <611> decided to use ACN as internal standard instead of the commonly utilized n-propyl alcohol.

Anyway: I'd try 0.5ul injection, as 1.0ul is pretty large for aqueous injections (the expansion of the water is larger than the liner volume). And try a slower injection speed.

CPG has stated good points and good advice.

Remember when you inject water containing samples at temperatures where water can condense to liquid you can be damaging the phase and the support when using capillary columns. Liquid water damages columns. This damage will increase with time and will increase the tailing.

best wishes,

Rod

thanks for advices

first i prepared sample in water. after that ı prepared new sample in dimethylsulfoxide but it gives same tailing.
can u offer an advice or any other column (DB-1301 or BP1 etc.)?

A PEG phase works well, but doesn't separate IPA well.

A porous polymer capillary column works well.

Many packed columns work.

best wishes,
Rod

Ethanol is sitting smack on top of the water on that column, a hard learned, long ago lesson. Only discovered this because of use of a different detector other than FID.

Best regards,

AICMM