Help me! Tune

[Thuypham]

Hi,

Yesterday, I changed column HP 5ms UI. Result is a little better separation. But there are a lot of ghost peak very hight and rising baseline and gain peak width: 0.1 min -> 0.2 min

I attached images:
http://imgur.com/a/5zATI

I hope to receive your help. Thanks a lot.
(Sorry for my English )

[James_Ball]

You may need to bake out the column if it is a used one that has not been installed for a long time. The ghost peaks can come from oxidized stationary phase being knocked off by the first few injections. Does the spectra of the ghost peaks look like it is siloxanes?

The high baseline will also be caused by the column not being baked out to remove oxidized stationary phase and should become less evident the more injections you make.

Wider peaks could indicate you need a little higher flow rate. Try adding 0.1 or 0.2 ml/min to the carrier flow rate.

[Thuypham]

Hi James_Ball,

Sorry for replying late. Thank you very much for your help.

Yes, there are peaks of siloxan.
And I did like your suggestion.
I baked out the column in 30 minute (at 300oC), and after about 10 injections, less ghost peak. However baseline still high. So, i decreased temperature program down 230oC to less rising baseline.