Preparation of micron and submicron particles via spray drying and electrostatic precipitation

Abstract

Small particles are of great interest in a variety of applications. Spray drying is a common technique for particle synthesis, but it is limited with respect to sizes below 10 μm. Therefore, a new laboratory-scale spray dryer was designed to address this issue. A novel aerosol generator consisting of a piezo crystal in a swirl chamber was designed to obtain droplets in the low micrometer range. After drying and cooling, particles were deposited in a molten carrier, using melt electrostatic precipitation. The median particle size of three pharmaceutical drug substances was 2 μm. The size distribution was particularly narrow, with span values of about 1.1. Spray drying is a sufficient technique to produce small drug particles below 5 μm with ultrasonic atomization at high frequencies. Electrostatic precipitation in a molten carrier is a suitable method to capture these particles.