Chromatography Forum

Hi All,

This is my first post to the Forum, and I'm a relatively new user of GCs, other than during my degree course, however I have recently started a job in the Scotch Whisky industry and I'm just looking for a little knowledge/advice as I get to grips with running the instrument (Agilent 7890).

Apologies for the length of post, hoping to explain everything clearly.

Basically, the lab runs whisky samples (in the range 40% - 94% Abv) through a CP-wax 57 CB FS (50m x 0.25mm 0.2µm film thickness) column to quantify the Higher Alcohol compounds ( Acetaldehyde, Acetal, Methanol, Iso Butanol etc.).

Liner, septum and gold seal were all changed recently. I've ran some samples of known values, and was getting varying results, so I ran some blank samples of 40% Ethanol (separate vials, from the same batch of analytical grade Ethanol) and got the below chromatograms:




Basically, just looking for any advice, does this look likely to be an issue with the column?

Thanks!

Conditioning the column may help , it seems there are some impurities trapped in the column.

Heat the column a little below the max operating temperature , it is around 240 C for Wax column , for at least two or three hours , then try again.

You may also increase the carrier gas flow ( around 2 ml / min ) to speed up the process.

It is a better practice to disconnect the column from the detector during clean up , in order to prevent the contamination of detector . Plug the detector inlet with a blind nut.

Scotch85,

Whenever you can see the noise of an FID, you are not getting enough on column. With an FID - generally - if it is lit it is pretty much working. So, if you can see the noise, it's not putting enough on. If the retention times are right, either your injection volume or your split ratio has changed significantly. Or.... your syringe is plugged. Start with the easiest - syringe - and go from there.

Even the second, "ugly" chromatogram is only 10 pA - not that much and probably related to the issues above.

More info gets you better suggestions :>)

Best regards,

AICMM