Rotenone coprecipitation with biodegradable polymers by supercritical assisted atomization

The aim of this study was to coprecipitate rotenone, a biopesticide, with biodegradable polymers using supercritical assisted atomization (SAA) process. Rotenone encapsulation can protect the pesticide from degradation thus reducing the quantity to be used. Different water soluble polymers were tested, such as polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and sodium alginate. Solutions with one or two solvents and rotenone suspensions were tested to perform the experiments. Different biodegradable polymer/pesticide ratios were tested: 2 and 8 in the case of PEG⿿rotenone coprecipitates, 25, 50 and 100 in the cases of PVP⿿rotenone and alginate⿿rotenone coprecipitates. The particles obtained were spherical with the mean diameter ranging between 0.6 and 1.5 μm. The effective loading of the particles was evaluated by HPLC and the best results were obtained in the case of alginate⿿rotenone coprecipitates that show a coprecipitation efficiency close to 100% and for PEG⿿rotenone particles the efficiency was about 98%. PVP⿿rotenone composite microparticles showed the lowest coprecipitation efficiency that ranged between 30% and 50%.