Hi, everyone,

The steroid I am working on shows much better sensitivity if there is more that 85% methanol in the MP on APCI negative mode. Currently I use Xterra MS C18 and MP of 80% methanol (k' about 2). Therefore, I need a more retentive column and hope that more organic is needed. Where and how to find a table listing retentivity for common RP columns?

Thanks in advance.

Most vendors would have some charts showing columns and their ability to retain typical analytes.

Use Symmetry C18. It has more retention that XTerra MS C18.

You can find this information in the selectivity chart in your Waters catalogue.

Thanks for your kind reply.

What about C30 and Graphite columns? Is the C30 more retentive than C18 for hydrophobic cpds?

A C30 column does not have more retention than a C18. For example, in my list of packings, Symmetry C18 has much more retention than YMC C30. This is partially due to access to the stationary phase, and partially due to other particle characteristics.

I do not have equivalent data for a graphite column, plus I think that it is more complicated and not so easy to predict. Therefore I do not know if a graphite column would give more retention for your compound.

Thanks!

Jimmy,
Try Phenomenex Synergi Hydro-RP (sorry, Uwe). I love it and always try first when need a C18.
Excellent for hydrophobic retention.
Good luck!

I tried Symmetry C18. It showed almost the same RT as on Xterra C18 with the same MP.

Jimmy