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Liquid chromatography at the critical condition: Thermodynamic significance and influence of pore size

Authors

  • Asem I. Abdulahad,

    1. Department of Chemistry and Chemical Biology, NYS Center for Polymer Synthesis, Rensselaer Polytechnic Institute, Troy, New York 12180
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  • Chang Y. Ryu

    Corresponding author
    1. Department of Chemistry and Chemical Biology, NYS Center for Polymer Synthesis, Rensselaer Polytechnic Institute, Troy, New York 12180
    • Department of Chemistry and Chemical Biology, NYS Center for Polymer Synthesis, Rensselaer Polytechnic Institute, Troy, New York 12180
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Abstract

Liquid chromatography at the critical condition (LCCC) is a high performance liquid chromatography (HPLC) technique that lies between size exclusion chromatography and adsorption-based interaction chromatography, where the elution of polymers becomes independent of polymer molecular weight. At LCCC, the balance between the entropic exclusion and the enthalpic adsorption interactions between polymers and stationary phases results in the simultaneous HPLC elution of polymers regardless of molecular weight. Using C18-bonded silica chromatographic columns with 5 μm particle size and different average pore size (diameter = 300 Å, 120 Å, 100 Å, and 50 Å), we report (1) the thermodynamic significance of LCCC conditions and (2) the influence of column pore size on the determination of critical conditions for linear polymer chains. Specifically, we used mixtures of monodisperse polystyrene samples ranging in molecular weight from 162 to 371,100 g/mol and controlled the temperature of the HPLC columns at a fixed composition of a mobile phase consisting of 57(v/v)% methylene chloride and 43(v/v)% acetonitrile. It was found that, at the fixed mobile phase composition, the temperature of LCCC (TLCCC) is higher for C18-bonded chromatographic columns with larger average pore size. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2533–2540, 2009

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