DETERMINATION OF FREE AMINO GROUP CONTENT OF SERUM-ALBUMIN MICROCAPSULES .2. EFFECT OF VARIATIONS IN REACTION-TIME AND IN TEREPHTHALOYL CHLORIDE CONCENTRATION

Microcapsules were prepared through interfacial cross-linking of human serum albumin (HSA) using terephthaloyl chloride (TC) at a constant p H of 9.8. Variations were performed in reaction time (for a 2.5% w/v T C concentration) and in TC concentration (for a 30 min reaction time). Determination of free amino groups was performed on lyophilized micro capsules by means of a back titration method using trinitrobenzenesulf onic acid (TNBS). When prolonging the reaction time from 2 to 30 min, microcapsule-NH2, content progressively decreased from 154 to 60 mu mo l/g dry weight. These results were in good agreement with those of a p revious study conducted using Fourier transform infrared spectroscopy. A slight recovery of free-NH2 was observed after 60 and 120 min. Incr easing TC concentration from 1 to 5% (w/v) resulted in a progressive d ecrease in microcapsule-NH2 content from 99 to 38 mu mol/g.