CN columns

[Mach]

It seems like a CN column is the only solution for my application. But the columns seem to degrade faster than i like. Any tips om how to prolong life-time? What to avoid, and how to regenerate? I am using at mobile phase with acetonitrile, methanol and phosphate buffer at pH 6-7.

[Uwe Neue]

It is the nature of the beast. Under your conditions, CN columns die MUCH faster than C18 columns.

[Mach]

Any suggestions for alternative and more stable columns for analysis of hexetidine?

[Uwe Neue]

I would run such a compound on either an XBridge Shield RP18 or a SymmetryShield RP18 column. Both are packings with an embedded polar group that will give you no headaches with tailing of bases. Also, both are stable at neutral pH. XBridge Shield RP18 is stable far into the alkaline pH: we use it routinely at pH 10.

[Mach]

I grabbed a 5.5x0.46 / 3um C18 column on the shelf and used a mixture of methanol/water/TFA/TEA and was able to get a useable peak. Not the best peak shape, but enough for the intended use. So bye bye CN!

[Uwe Neue]

I am glad that you are getting something useful. However, one of the packings mentioned above with the embedded polar group will not give you any tailing.

[Mach]

Peak shape is probably also influenced by the fact that my compound is a isomere mixture.

I will consider one of these columns, as I will need a "high" pH column in my stock. Which one would you recommend for alcaloids?

[Uwe Neue]

If you want to go to high pH, you need to use the XBridge column.