The effect of resin type, degree of cross-linking, bead size, and surface area on the
phosphate and
bile salt binding characteristics of five strongly basic
Dowex anion-exchange resins in the
chloride form was studied. The maximum uptake of
phosphate (expressed as uptake of
phosphorus) from
sodium phosphate solutions was 137, 82, 86, 138, and 76 mg of
phosphorus per gram of dry
Dowex resins XF 43311, XY 40013, XF 43254, XY 40011, and XY 40012, respectively. The presence of simulated gastric or intestinal fluids resulted in small but insignificant alterations in
phosphorus uptake by the resins. The resins all bound similar amounts of
phosphorus and
taurocholate (80-100% of the total
phosphorus and
taurocholate in
solution) at physiological concentrations of
phosphate and
bile salt.
Dowex resins XY 40013 and XF 43254, with identical physicochemical properties, but different bead sizes and surface areas, bound similar amounts of the
bile salt sodium taurocholate at all
taurocholate concentrations, indicating that binding was not restricted to the surface sites on the resin bead. The 2% cross-linked resins bound 3-4 times more
taurocholate than the 8% cross-linked resins (at high
taurocholate concentrations); the smaller pore size of the latter resins probably presents a greater mechanical exclusion barrier than the larger pore size of the 2% cross-linked resins.