Problem with separation of ketone and its diketone impurity

[martas]

I have problem with separation of ketone of saturated cyclic hydrogencarbon and its diketone impurity.

Does anybody have some idea how to perform GC analysis? Is derivatisation possible?

I use Ultra-II column, 50 m length.

Thank you for your comments,
Martas

[HbJ]

Please tell us (the forum) your temperature program, the other dimensions of the column (internal diameter, film thickness), your injection parameters (injector temperature, split), type and pressure of carrier gas and if you can resolve the two peaks at all.

Generally speaking an OV-7 (20% phenyl/80%methylsilicone) might do the job as that phase allowed me to separate a quite similar analyte quite well.

[martas]

Chromatographic conditions in detail:

Column: HP Ultra–2, 50 m x 0,32 mm, film 0,52 um
Carrier gas: helium, 1,2 ml/min
Injection volume: 1 µl
Temperature programme: 150 °C - 2 min, gradient 15 °C/min to 250 °C, 20 min
Injector temperature: 220 °C
Detector temperature: 280 °C
Splitter: 30 : 1

M.

[HbJ]

Why are you using such a steep gradient (15°/min!) with a column of 50m?

And what are the boiling points of your analytes? (hint: exploit the differences!)
What solvent do you use? (or do you inject the undiluted sample?)

But anyway you might try the following method:
150°C/5 min => 5°C/min => 250°C/20 min.

Then check if the peaks resolve and please tell us if you resolve your peaks now.

[HbJ]

What's the current state of affairs?