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

Abstract

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.