Agilent HPLC Column Selection Guide

HPLC Column Selection GuidelinesSelect from Agilent ZORBAX Eclipse Plus Phenyl-Hexyl,Eclipse XDB-Phenyl, CN and Bonus-RPThe method development process at mid pH mimics the process at low pH with optimizationof the organic modifier and selecting an alternate bonded phase if resolution is not achievedafter that step. The alternate bonded phases at mid pH are the Eclipse Plus Phenyl-Hexyl,Eclipse XDB-Phenyl, Eclipse XDB-CN and Bonus-RP. They provide very different selectivitiesfor many samples and the method development process is followed again. The Bonus-RPcolumn has a polar embedded amide group that provides different selectivity for manysamples, provides good peak shape for basic compounds and allows the column to be usedwith up to 100% aqueous mobile phases.Choose Agilent ZORBAX Extend-C18 columnsfor method development at high pH (pH 9-12)At low or mid pH, some separations of basic compounds may still not have enough retentionor the desired selectivity. For these samples, high pH separations may be appropriate. Untilrecently, high pH separations on silica-based columns were avoided because of short columnlifetimes, due to dissolution of the underlying silica gel. Newer column technologies, i.e. theZORBAX Extend-C18, can protect the silica from dissolution, so that a reasonable columnlifetime can be achieved and the selectivity advantages of high pH can be explored.The mobile phase buffer choices at high pH with the Extend-C18 column are organic bufferslike triethylamine and ammonium hydroxide. These buffers are best used with methanol asthe organic modifier to extend the column lifetime at high pH.16 Order online at www.agilent.com/chem/store