Residual solvents in API by Headspace GC

[smathkar]

I am trying to get good peak shape of Methanol on DB-624 (30mX0.32mmID, 1.8um FT) by Headspace GC. The tailing factor of the peak is >2. How do I improve it? When Eur.Ph, USP mtd GC conditions were used, the peak worsened. Your suggestions are welcome. I have tried different conditions but no use.

[Jam]

Hey,

I'm dealing with Ethanol and methanol at the moment, even thought the column I'm using is of different phase (BD-5) and the injection mode is not headspace, but direct split injection. Anyhow, both of the peaks were very tailing first, but it turned out that the two main reasons for that were the too large injection volume (which produced too much vapor in the liner) and probably the column contamination (a piece of the column inlet head was cut off and the column is now being cleaned on regular basis with higher temperatures > 200 °C).
We tested also the liner with and without a glass wool, and it turned out that the glass wool is really needed because of the reproducibility issues.
then I tested for curiosity the recommended phase for alcohol analysis (f. ex. Stabilwax (carbowax PEG)) and the peaks are tailing more than before, so the optimum phase for my purposes will be BD-5.

I hope this helps a little, good luck.

[lpnian]

hi
I think the the big inject volumn in headspace also can cause tailing ,you can try to use spilt mode.i hope my recommend will help to you.

[Carlos Teixeira]

Dear Friend:

A - We have performing this analysis, but with good results for these analytes (MeOH, EtOH, etc) in GC-HedSpace.

B - When somebody have difficult with Tailing it is posstible solve it with highest temperature, the Eur. Pharm has a limit for increasing the chromatograph parameter without the need of GC-method (re)validation.

Important: Remember that: if you to change the column you must validate your Residual Solvent method.

C - I have three questions:

1 - Are you using the concentration of your analyte in the range of Residual Solvent from EP 5th ed.?

2 - Are you using one correct setup in your GC system (like as liner, column's adaptation, oven's temperature?

3 - Is your equipment Ok?


Best regards,


Carlos Teixeira

[dezelana]

To Carlos Teixeira:
We have got high tailing too for methanol and other alcohols using AT-624 30mx0,53x3 and AT-624 30mx0,32x1,8 Ph. Eur. method.
However what did you mean by C2-column's adaptation?

Bye
ana