Resumen de Investigating the Retention Mechanisms of Liquid Chromatography Using Solid-Phase Extraction Cartridges
Mary E. O'Donnell, Beata A. Musial, Stacey Lowery Bretz, Neil D. Danielson, Diep Ca
Liquid chromatography (LC) experiments for the undergraduate analytical laboratory course often illustrate the application of reversed-phase LC to solve a separation problem, but rarely compare LC retention mechanisms. In addition, a high-performance liquid chromatography instrument may be beyond what some small colleges can purchase. Solid-phase extraction (SPE) cartridges offer an inexpensive alternative, while still providing effective model columns for investigating LC retention mechanisms. We have shown that the four major retention mechanisms (normal-phase, reversed-phase, ion-exchange, and size-exclusion) can be investigated experimentally using two types of SPE cartridges (silica and C18) as columns. The C18 cartridges can be pre-treated with anionic or cationic polymers to produce ion-exchange columns. The concept of post-column detection is also introduced. This experiment is suitable for a first-year general chemistry course or a third-year analytical course to illustrate the importance of solvent polarity and the types of retention mechanisms employed in separation science
