Organic porous polymer monolithics (PPM) are a newer type of stationary phase, structurally distinct from traditional silica based phases. They behave differently and often provide superior separations, but have not been fully characterized. Unlike traditional phases, they consist of a single macromolecular porous structure that is highly permeable. Furthermore, they do not require frits for stable placement in columns. The lauryl acrylate (LA) columns we have developed and worked with are remarkably reproducible from batch to batch and have proven to be quite durable. We have been examining these monoliths in both HPLC and capillary electrochromatography (CEC) modes. We are examining the relationship between diffusion and retention in order to better understand the behavior of analytes with these materials. The thermodynamics of retention and diffusion are also being probed. By better understanding this stationary phase, and comparing results to more traditional materials, we hope to add to the fundamental understanding of the nature of mobile phase, stationary phase, and analyte interactions.The peak parking method was used to characterize analyte diffusion on a LA-PPM. Analytes with a wide range of retention factors were investigated by CEC with UV detection. Analyte elution was stopped mid column and samples were allowed to diffuse for varying amounts of time. The relationship between the resulting peak variance and diffusion time yields the diffusion coefficient of the analyte. In the column with stationary phase, the effective diffusion coefficient (Deff ) is obtained. The diffusion coefficient of the analyte in the mobile phase (Dm) is determined in open columns. The relation between retention factors, Dm and Deff are then modeled. Experiments are conducted at different temperatures to obtain thermodynamic data. Retention factor varies with analyte identity, but different mobile phase compositions were also used to alter retention. Our most recent results will be discussed.

Organic porous polymer monolithic stationary phase studies: Diffusion, retention, and thermodynamics

247th National Meeting (2014)

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