Analysis of Liquid Particles in Aerosols via Charge-Induction Amperometry (ALPACA) for Rapid Electrospray Droplet Charge Analysis.

The rapid and on-line study of aerosols and their properties is technically demanding due to their small size (<10 μm diameter) and the resultant required scale of any such measurements. Most such techniques require the use of lasers (e.g., phase Doppler anemometry), condensation growth, or other complex hardware. To this end we introduce analysis of liquid particles in aerosols via charge-induction amperometry (ALPACA), an extremely simple potentiostat-based technique capable of on-line, rapid measurement of the aggregate charge of aerosol particles. This technique demonstrates high signal-to-noise responses, is not subject to chemical noise, and has the potential for significant future miniaturization. This technique is applied in this work for the detection of charges on electrosprayed droplets. The mechanism of detection of the technique is discussed using both amperometry and open circuit potential (OCP) to measure droplet charge properties. ALPACA represents a significant advancement toward simple, inexpensive aerosol charge detection.