Investigate particle size distributions of electronic cigarette aerosols using a multi-angle light scattering instrument
Particle size distribution measurement of electronic cigarette aerosols represents a great experimental challenge due to the volatile nature of the particulate compositions and the high number density (up to 1010 per cubic centimeter). Efforts have been made to measure particle size distribution of e-cigarette aerosols in recent studies using techniques such as electrical mobility, cascade impactor and spectral light transmission method. In this study, we demonstrate the capability of a newly developed multi-angle light scattering instrument to accurately measure particle size distribution and mass concentration of e-cigarette aerosols in real time without sample dilution. The instrument, developed by EnviroMetrix Instruments, uses laser light scattering collected at three angles (10, 40 and 90 degree) to calculate the total particle size and number concentration, based on MIE theory. Once the size and distribution width are determined by a proprietary algorithm, the particle number, mass, and surface area are computed from these parameters over a wide dynamic range. It is capable of measuring particles with sizes range from 50 to 1000 nm and mass concentrations range from 0.1 to 100000 mg/m3 at up to 50 Hz data rates. Several different e-cigarettes were evaluated using the instrument under a constant flow, square wave puff profile (55 mL puff volume and 3 second puff duration) and approximately 80% mass closures, relative to filter pad measurement, were obtained. The average mass mean diameters of the tested e-cigarette aerosols were observed to fall between 350 and 450 nm, and these values are comparable to particles found in tobacco burn-down cigarette aerosols. The real-time mass concentration and mass mean diameter measurements provide valuable information for product developments and evaluating the behavior of e-cigarette aerosols in the respiratory tract.