AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Aerosol Microconcentration for Aerosol Measurement Using Optical Spectroscopies
LINA ZHENG, Pramod Kulkarni, Huayan Liang, Konstantinos Zavvos, G.J. Deye, M. Eileen Birch, Dionysios Dionysiou, Centers for Disease Control and Prevention, NIOSH
Abstract Number: 546 Working Group: Instrumentation and Methods
Abstract Efficient microconcentration of aerosols to a substrate is essential for effective coupling of the collected particles to microscale optical spectroscopies such as laser-induced or spark microplasma and Raman spectroscopy. The spatial extent of the microplasma or the laser beam is on order of few hundred micrometers, requiring efficient microconcentration of aerosols to allow sensitive detection of analytes. Further, for effective microconcentration in a portable instrument, the following key operating requirements are important: i) the efficiency of collection must be independent of particle size, ii) the pressure drop must be low, and iii) the entire collected particulate mass must be available to the laser or microplasma to achieve high signal-to-noise ratio and analytical sensitivity. We present design, characterization, and optimization of an electrostatic aerosol concentration method for portable analytical instrumentation. The method involves a set of coaxial electrodes separated by few millimeters, one held at high potential and the other grounded. The particles are collected on the ground electrode from a coaxial flow in a one-step charge-and-collect scheme using corona on the high voltage electrode. Collection characteristics of this system were investigated as a function of operating parameters such as flow rate, corona current, particle size, and electrode diameter. Atomic emission signal from spark microplasma was used as a metric representing analytical signal-to-noise ratio. Electrohydrodynamic simulations were conducted to obtain insights into particle transport and deposition. Scanning electron microscopy was used to probe distribution of collected particles on the electrode. We show that optimum combination of flow rate and electrode diameter exists that provides highest analytical sensitivity that is independent of particle size in the submicrometer size range. We also show that the electrostatic microconcentration used in this work provides highest sensitivity compared to similar collection using aerodynamic lens or filters, especially with respect to the pressure drop incurred in respective system.