Formula and process optimization of controlled-release microcapsules prepared using a coordination assembly and the response surface methodology

A model chlorpyrifos microcapsule was prepared using coordination assembly between Fe 3+ and tannic acid (TA). The influence of independent variables such as the dropping rate of TA ( X 1 ) and Fe 3+ ( X 3 ), the concentration of TA ( X 2 ) and Fe 3+ ( X 4 ), and the reaction temperature ( X 5 ) on the encapsulation efficiency ( R 1 ) and release characteristics ( R 2 ) of the microcapsule had been investigated, based on a central composite design with five factors and five levels. The results showed that the main factors influencing R 1 and R 2 were X 4 and X 2 , then the interaction between X 2 and X 4 , followed by X 5 and X 3 . The optimal formula mainly based on higher R 1 and lower R 2 were determined and then tested. The optimized conditions led to an encapsulation efficiency and cumulative release proportion of 97.12% ± 0.72% and 40.07% ± 0.53%, along with the average relative errors of predicted values being 1.78% and −1.60%, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132 , 42865.