Has anybody found any advantages to using a Phenyl-Hexyl phase versus a traditional propyl linked phenyl phase or alkyl phase. It is my understanding that they are more stable under alkaline conditions than traditional phenyl phases and may offer the combined selectivity of alkyl and phenyl phases.

The hexyl linkage is more stable than the propyl (in general, the longer the chain the more stable the linkage). Your best bet though is to give it a try for yourself and let us know how you fair. Added stability does not do you any good if the column does not have the right selectivity for your separation. The extended pH range and thus selectivity you can achieve with the phenyl hexyl may be yet another plus in its favor during method development.

A couple of things I have noticed with the Phenyl-hexyl phase:
1. Overall retentivity is similar to a C8, but has some higher affinity for aromatic compounds due to phenyl ring
2. This phenyl selectivity is more noticeable when using methanol as organic versus acetonitrile. This applies to all phenyl phases I have used.
3. pH stability is good - we run an assay at pH 9.5 and have no problem with silica dissolution.

Can anyone offer information on the HPLC media called 'EuroSphere' ??

All information would be appreciated.

Can anyone offer any information regarding the gradient profile reproducibility of using phenyl-hexyl columns in gradient HPLC at low wavelength detection (214 nm). Even with a new column, gradient profiles are not reproducible using water/ACN gradient systems (going to about 70% ACN). Any equilibration recommendations would be appreciated. We have even removed the buffers and have tried cycling gradient profiles using only water/acetonitrile. Replicate profiles are still not reproducible (the HPLC system is calibrated and operately properly...) Any ideas would be greatly appreciated!!!