SPATIALLY RESOLVED MEASUREMENTS OF SIZE AND VELOCITY DISTRIBUTIONS OFAEROSOL DROPLETS FROM A DIRECT INJECTION NEBULIZER

Aerosol droplet sizes and velocities from a direct injection nebulizer (DIN) are measured with radial and axial spatial resolution by phase Doppler particle analysis (PDPA). The droplets on the central axis of the spray become finer and their size becomes more uniform when almost -equal-to 20% methanol is added to the usual aqueous solvent. This cou ld explain why the analyte signal is a maximum at this solvent composi tion when the DIN is used for inductively coupled plasma-mass spectrom etry (ICP-MS). Mean droplet velocities are 12 to 22 m s-1 with standar d deviations of +/-4 to +/-7 m s-1. The outer fringes of the aerosol p lume tend to be enriched in large droplets. The Sauter mean diameter ( D3.2) and velocity of the droplets also vary substantially with axial position in the aerosol plume.