split peaks

[kvalliappan]

Hi!

Last week we had an interesting observation. One of research scholars started using a fresh cyano column (Phenomenex). As a protocol an inhouse test mixture (containg uracil, acetophenone and toluene) was injected first to record the efficiency of the colum. Mobile phase was 50% ACN as suggested in the column brochure. An isocratic run. We have a mixer unit in the system. UV detection at 254. We noticed that all the three peaks were split at the top. We couldn't fix the problem yet. But a C18 column (supleco) resolved the mixture into three components, no peak splitting was observed.

I would appreicate if someone could help me to find a solution.

[DR]

1) Do the connections on the 2 columns require the same depth of tubing? If not, and you have a gap at the head of the column, this may be the root of the problem.

2) Do you still get the split peak tops if you premix the mobile phase? If not, you have a mixing issue. If you do, the column may be damaged (has a void in it). Try another column of the same type.

[HW Mueller]

In what did you dissolve your test mixture?

[Koen Hollebekkers]

Another possibility is that there is some material at the head of the column. I sounds strange since the column is new. There are different possibilities which could caused this blockage, this is just suggestion.
I hope you have still guaranty on your column.

[Uwe Neue]

It could be that your sample solvent is too strong, or it could be that your cyano column is dead. Having a very high opinion about CN columns, I think the latter is the case...

[kvalliappan]

Hi! Thanks for the response. The sample solvent is the mobile phase (50% ACN), as given in the column brochure.