column oven

[fin]

Hi everybody, I'm new to this whole thing so please bear with me if I ask a stupid question or don't make sense!

I have recently acquired an oven for a column I'm using in an HPLC-MS system. The point of the oven I've been told is to improve and narrow the peaks produced and this seems to be backed up by anything I've read. Unfortunately the results I'm getting are the opposite with lots of tailing! I've tried playing around with the flow but this hasn't helped!

Has anyone any ideas or suggestions? I think it's probably due to my inexperience so any suggestions that seem really simple or obvious would be a real help!

Thanks a million,
Fin.

[Noser222]

How much higher in temperature did you go? What kind of column and mobile phase?

Higher temperature helps in some cases more than others, but I'm not sure why you'd get more tailing at a higher temperature than at room temperature.

[Dan]

Fin,

Check your tubing and fittings.

I am sure that you added extra tubing in order to connect the column oven. Did you use the correct tubing and fittings? Extra dead volume in the area between the injector and the column can lead to broader peaks.

Regards,
Dan

[zokitano]

What are you trying to separate? Are you sure that you're using the proper column or does your mobile phase is adequate for your analysis. What kind of column are you using? And what is the composition of your mobile phase?

Maybe, you're getting peaks with tailing due to the bad choice of mobile phase or/and column.

Best regards

[tom jupille]

Fin, more details would help in diagnosis but, in addition to what has already been suggested, remember that if you are running your column substantially above ambient temperature, you need to include provision for preheating your mobile phase (solvent) before it gets to the column. If you pump cool solvent into a heated column, you set up a temperature gradient along the length of the column (inlet is cooler than the outlet) and across the diameter of the column (center is cooler than the walls). That can make different parts of your peak move at different rates and result in tailing, flat-top peaks, split peaks, broad peaks, etc. (depending on the details).

[fin]

Oh thanks a million everybody for your replies-I'm sure I'll be busy for a while trying your suggestions! It's a C18 column, looking for thyroxine (T3 and T4) using ammonium acetate/ acetonitrile mobile phase gradient. The trial has been going well for a few months so I know that the column and mobile phase and all are fine for what I'm looking for.

What I didn't take into consideration was dead volume and preheating the mobile phase!!!

So thanks a million for that-I'll let you know how I get on!

Slan,
Fin

[DR]

Also, while elevated temperatures can be used to alter retention and narrow peak widths, tailing problems are frequently immune to temperature (eg: very narrow peaks can still tail horrendously).

If you have basic analytes, you may have to reconsider your starionary phase (column packing) choice to reduce tailing.