Gelatin Carbopol

El Gindy and El Egakey (1981a,b) investigated the coacervation of gelatin A or B and Carbopol 934, 940, or 941 (source: B. F. Goodrich Chemical Co.). The two polymers were dissolved separately at 40°C, and the gelatin solution was added to the stirred Carbopol solution and various parameters were altered to investigate the system. Best results were obtained with gelatin type A at a pH of 6.8 with Carbopol 941 and the optimum ratio of Carbopol to gelatin was 1:10. An increase in total colloid concentration up to 1.1% w/v resulted in a parallel increase of sediment weight. At higher concentrations the sediment weight was less pronounced. Stirring at 300-350r.p.m. gave almost spherical uniform coacervates with an average diameter of 59 /¿m.

In a subsequent paper, El Egakey and El Gindy (1983) found that glycerol in 20-33% v/v added after coacervation, produced smooth, spherical coacervates and if glycerol was added to the Carbopol solution prior to coacervation a coarser product was formed. The addition of glycerol rendered the microcapsules less coherent and reduced their adhesion to glass. The effect of increasing the concentration of formaldehyde was to increase the sediment volume of the coacervate. Formaldehyde-treated microglobules were treated with various volumes and concentrations of alcohols. The floccula-tion and sedimentation efficiency showed that 2-propranol at 60% concentration gave the best results. Microcapsules of sulfadiazine encapsulated with the gelatin-Carbopol coacérvate were also prepared. As the coat to core ratio increased, the percentage of drug encapsulated increased, and the average size increased from 78 to 136 /¿m.

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