In-situ characterization of e-cigarette aerosols by 90°-light scattering of polarized light

Abstract

The polarization ratio method is used for fast in-situ characterization of unimodal condensed aerosols of e-cigarettes. The method is based on 90°-light scattering of polarized 680 nm laser light by the droplet ensemble inside an optically defined measuring volume. Mass median droplet diameter (MMD) is derived from the ratio of scattered light from horizontally and vertically polarized incident light beams assuming a fixed value of the geometric standard deviation of the aerosol mass distribution. MMD is used to correct for the size dependence of the mass-based scattering signal of vertically polarized light to obtain the mass concentration if the sensor is calibrated once with an aerosol with a fixed MMD. The sensor uses commercially available aerosol photometers, and its application to e-cigarette aerosols was validated with an impactor for MMD and with a filter measurement for mass concentration. Good correlation (r2 > 0.97) for both parameters was observed. Application ranges are mass concentration range 0.5–50 mg/L, MMD 0.2–1.2 µm, 100 ms time resolution, and 0.2–3 L/min flow rate. The usefulness of this simple sensor for e-cigarette aerosol characterization is demonstrated by developing a scaling law between MMD and operating parameters of an e-cigarette, i.e., puff flow rate and mass concentration. Copyright © 2018 American Association for Aerosol Research.