Liquid chromatography and differential scanning calorimetry studies on the states of water in hydrophilic polymer gel packings in relation to retention selectivity

The amounts of water which exhibit selectivity to solutes in water-swollen hydrophilic polymer gel packings were determined by a liquid chromatographic method designed on the basis of the mobile phase electrolyte effects on the retention of ionic solutes. The estimated amounts of the water in three types of water-swollen hydrophilic polymer gels, a cross-linked dextran, poly(vinyl alcohol) and polyacrylamide, agree well with the sum of the amount of freezable bound water and that of non-freezing water determined by means of differential scanning calorimetry. Retention selectivities of these packings were evaluated based on the plots of logarithmic distribution coefficients, In K-D, of various organic compounds obtained on one packing versus those on another with the same mobile phase, water. It was found that the In K-D vs. In K-D plots between two packings of the same polymer matrix with different degrees of cross-linking were linear and the slopes of the plots depended on the fractions of the freezable bound water and the non-freezing water in the stationary phase; the water-swollen hydrophilic polymer packings which contained a smaller fraction of the freezable bound water exhibited larger retention selectivities. (C) 1999 Elsevier Science B.V. All rights reserved.