Basic Information
Abstract Number: 2380-4    
Author Name: Jing Liu Affiliation: Trinity University
Session Title: Separation Sciences I
Event Type: Oral
Event Title: Fundamental Studies of Porous Polymer Monoliths, Exploring the Thermodynamics of Retention and the Relationship Between Retention and Diffusion
Presider(s): Zewe, Joseph Start Time: 09:00 AM ( Slot # 4 )
Date: Thursday, March 15th, 2012 Location: 307C
Keywords: Capillary Electrophoresis, HPLC Columns, Separation Sciences, Temperature

Bushey, Michelle MTrinity University
Kuklinski, Nicholas JTrinity University
Lam, Jessica KOberlin College
Li-Gonzalez, Si YingTrinity University
Nolan, Douglas TTrinity University
Patel, Trisha HTrinity University

Abstract Content
Capillary electro-chromatography (CEC) is a cross between HPLC and capillary electrophoresis. The technique utilizes a stationary phase like HPLC, but rather than moving the mobile phase with high pressure, CEC drives mobile phase through by electroosmotic flow. The purpose of this study was to improve understanding of the types of interactions that occur between the analyte, stationary, and mobile phases for PPMs used in CEC systems. PPMs are structurally very different from traditional particle based stationary phases and have not been well characterized. Lauryl acrylate PPMs were used as the stationary phase. A wide range of analytes such as alkyl benzenes, polycyclic aromatic hydrocarbons, and parabens, with retention factors ranging from 0.1 to 13.4 were tested. Diffusion studies, utilizing a stopped flow method, were conducted for each analyte for 15, 30, 45, 60, or 75 minutes on both polymer filled columns and open capillaries. The peak variance measured in unstopped runs was subtracted from that measured in stopped runs, and the resulting difference is the variance due to the diffusion of the analyte. By plotting the peak variance versus diffusion time, the diffusion coefficient is obtained (Dm in the open capillary and Deff in the polymer filled columns). The relationship between diffusion and retention can then be examined by plotting (1+k)Deff/Dm versus k. This is based on the relationship: (1+k)Deff/Dm = γm + kγsDs/Dm. Such a plot is expected to produce a straight line with the obstruction factor (γm) as the intercept and the kinetic parameter (γsDs) obtainable from the slope. Retention factors were also determined as a function of temperature. In thermodynamics studies, retention factors of each analyte were obtained at 25C, 30C, 35C, 40C, 45C, 50C, 55C, and 60C. The relationship between retention and temperature can be examined by plotting In k versus 1000/T. The resulting van’t Hoff plots yield the enthalpy and the estimated entropy of partitioning. As the temperature increases, it becomes less favorable for the analyte to stay in the stationary phase. Both studies show that PPMs used in CEC modes display behavior quite distinct from traditional particle based phases and HPLC systems. This work was supported by NSF CHE-1055516, ACS-PRF 50594-UR5, the Welch Foundation, and Trinity University.