The gateway to difficult separations, selectivity or efficiency?

Separations scientists are facing an increasing number of HPLC Columns that are offering either orthogonal selectivity or extremely high plate numbers (efficiency) compared to those available say, 5 years ago. When faced with new separations that need to be performed, and in many cases these are getting more complex, which route do they opt to pursue at the method development stage? Much recent commercial activity has seen the promotion of ultra high efficiency columns, either by virtue of small particle sizes or use of elevated temperature (or both) as an option but we also have some unique novel chemistries, which are designed to offer alternate selectivity to the ‘traditional’ end-capped C18 (L1 designation in the US Pharmacopoeia). In this two-part article we shall examine the advantages of each route along with the shortfalls and show examples of successful separations.