STUDIES ON DIFFUSION IN ALGINATE GELS .1. EFFECT OF CROSS-LINKING WITH CALCIUM OR ZINC IONS ON DIFFUSION OF ACETAMINOPHEN

The permeability of acetaminophen in hydrated alginate and alginic aci d gels was measured using side-by-side glass diffusion cells. Gel film s were prepared by cross-linking sodium alginate films in aqueous solu tions (0.1 to 0.7 M) of calcium or zinc acetate for 1 to 30 min at 25 degrees C. Films prepared in 0.34 M cation solution for 15 min were ei ther exposed to Simulated Gastric Fluid USP minus pepsin, or dried at 45 degrees C to constant weight and then rehydrated, prior to a diffus ion study. Acetaminophen permeability in the gel films decreased with increasing divalent cation concentration and cross-linking time until an apparent optimum was reached. The decreased permeability was sugges ted to be due to increased cross-linking in the gelled structure. The permeability of acetaminophen in the gel films decreased in the order alginic acid gel films > acid-exposed alginate gel films > divalent al ginate gel films. Dehydration decreased the permeability of acetaminop hen in the Ca alginate gel films. Overall, there was little difference between the permeability of acetaminophen in Ca or Zn alginate gel fi lms.