Molecular weight distribution (MWD) and structural deformation of ultrahigh molecular weight (MW) sodium hylaluronate (10(5)-10(8) g/mol) were studied under different sample dissolution temperature conditions, using on-line flow field-flow fractionation (FlFFF) and multiangle light scattering (MALS). Sodium hyaluronate (NaHA) materials from sarcoma fluid have been studied by dissolving them in water at three different temperature conditions (5 degrees C, 50 degrees C, and 90 degrees C). Frit inlet asymmetrical flow field-flow fractionation (FI-AFlFFF), with field programming, was utilized for the separation of NaHA by MW, and on-line observation of light scattering of fractionated NaHA by MALS was performed in order to determine the MWD and molecular conformation. In these experiments, NaHA molecules exhibited an extended structure from a formerly rather compact geometry when the dissolving temperature was raised to 90 degrees C. This study also showed a clear difference in the MWD of NaHA when a preliminary filtration process was applied.