title: Thermodynamic analysis of the nonspecific interaction of sodium dodecyl sulfate with swollen Bio-Gel beads.
abstract: In frontal gel chromatography on Bio-Gel P-2, sodium dodecyl sulfate (SDS) at the concentrations below its critical micelle concentration (cmc) showed anomalously high partition coefficients (Kav obs) indicative of strong interactions with the swollen gel phase; further, Kav obs was found to increase with concentration and temperature. This preferential partition of SDS in the Bio-Gel phase was analyzed in terms of the transfer free energy of SDS from the mobile phase (0.1 M NaCl) to the swollen Bio-Gel phase. The results showed that the overall transfer process is primarily governed by hydrophobic free energy arising from the anomalous nature of hydrated water in the gel matrix; that is, in highly hydrated water "iceberg" formation is evidently limited and the hydrophobic free energy is accordingly lowered, resulting in the preferential partition of SDS in the swollen Bio-Gel phase. The increase in the negativity of transfer free energy with concentration, though relatively small, indicated a definite tendency for the formation of SDS clusters in the gel phase. Finally, a model illustrating the states of SDS molecules in the gel matrix is presented, which may also be pertinent to SDS-protein and SDS-amylose complexes.
mesh_terms: D002850:Chromatography, Gel / Q000379:methods*; D004735:Energy Transfer; D006358:Hot Temperature; D007700:Kinetics; D012967:Sodium Dodecyl Sulfate; D013816:Thermodynamics; D014867:Water
chemical_list: D014867:Water; D012967:Sodium Dodecyl Sulfate