Preparation Of Insect Sex Pheromone Dodecanol Containing Microcapsules By Coacervation And Their Controlled Release

In this work microcapsules with dodecanol (C12OH) encapsulated were prepared through complex coacervation by adding gelatin (GE) solution to gum acacia (GA) solution and through GE simple coacervation by adding sodium sulfate solution to GE solution, both in presence of C12OH. C12OH was chosen for the core material because it exists as a real component in sex pheromones of several insects. Moreover, the release mechanism of C12OH from microcapsules was primarily explained.In a first step, the behaviors of GE (Type A) and GA during the process of complex coacervation and simple coacervation were investigated. It was observed that, for complex coacervation, maximum yield was achieved when pH value of the mixture of GE and GA solution was adjusted to 4.2 and GE/GA weight ratio at unity, and for simple coacervation when 30mL of 20% solution of sodium sulfate was added to 40mL of 6% GE solution.In addition, the optimum conditions for encapsulating C12OH, especially by complex coacervation, were found. The results showed that a higher C12OH loading was observed when GA was first mixed with C12OH, with Tween20/Span80 (1:1) as dispersants, formaldehyde or glutaraldehyde as crosslinking agents and with a stirring rate of 400rpm. Other conditions for higher C12OH encapsulation rates were also studied, such as concentration of wall materials, ratio of C12OH to GE and GA. When wall material concentration was equal to or higher than 3%, the size of the microcapsules from complex coacervation was larger than those prepared through simple coacervation. Nevertheless, simple coacervation led to capsules with much narrower size distribution. C12OH encapsulation rates in simple coacervation were significantly lower compared with those in complex coacervation at equal wall material concentration, leading therefore to a lower C12OH loading in simple coacervation. As to microcapsules prepared at different crosslinking level, particle size and size distribution data showed that particle size decreased with a narrower size distribution when crosslinking agent was increased. C12OH encapsulation examination disclosed that crosslinking could remarkably enhance C12OH encapsulation.To investigate C12OH release from the capsules, samples were placed into an incubator at constant temperature (35℃) and relative humidity (50% RH), and taken out for C12OH examination both by gas chromatography and gravimetry. It was found that all samples from simple coacervation reached their final release in less than one week, no difference was observed for samples prepared with different wall material concentration; whereas microcapsules from complex coacervation manifested a three-step-release profile, i.e. a quick start followed by a constant plateau region and terminated by a release increase till completion.This work indicates that release of C12OH can be well controlled through capsule structure design. This is of great importance for our on-going study on controlled release of authentic insect semiochemicals.