Characterization of an aerosol microconcentrator for analysis using microscale optical spectroscopies

Abstract

Efficient microconcentration of aerosols to a substrate is essential for effectively coupling the collected particles to microscale optical spectroscopies such as laser-induced or spark microplasma, or micro-Raman or infrared spectroscopies. In this study, we present detailed characterization of a corona-based aerosol microconcentration technique developed previously (Diwakar and Kulkarni, 2012). The method involves two coaxial electrodes separated by a few millimeters, one held at a high electrical potential and the other grounded. The particles are collected on the collection (i.e., ground) electrode from a coaxial aerosol flow in a one-step charge-and-collect scheme using corona discharge and electrical precipitation between the two electrodes. Performance of the corona microconcentration method was determined experimentally by measuring collection efficiency, wall losses, and particle deposition density. An intrinsic spectroscopic sensitivity was experimentally determined for the aerosol microconcentrator. Using this sensitivity, we show that corona-based microconcentration is much superior to alternative methods, including filtration, focused impaction using aerodynamic lens, and spot collection using condensational growth. The method offers unique advantages for compact, hand-held aerosol analytical instrumentation.

Rapid Elemental Analysis of Aerosols Using Atmospheric Glow Discharge Optical Emission Spectroscopy

“…Detailed description of design and performance of CAM was provided elsewhere. 26 Briefly, the CAM consisted of two coaxial electrodes with an interelectrode distance of 4 mm. A high positive potential (~5 kV) was applied to the corona electrode through a DC power supply (Bertran S-230, Spellman Corp., Hauppauge, NY, USA).…”

“…A corona-based microconcentration method 26 was used for microscopic collection of airborne particles, followed by elemental analysis using rf-GD-OES. A methodology was developed for automated and semi-continuous analysis of aerosol.…”

“…The objective of this study was to develop a near real-time technique for aerosol elemental analysis using a low-cost atmospheric radio frequency glow discharge (rf-GD) excitation source. A corona-based microconcentration method 26 was used for microscopic collection of airborne particles, followed by elemental analysis using rf-GD-OES. A methodology was developed for automated and semicontinuous analysis of aerosol.…”

Quantification of toxic metallic elements using machine learning techniques and spark emission spectroscopy

“…Diwakar et al employed spark emission spectroscopy coupled with a corona aerosol microconcentrator (CAM) to improve the particle collection efficiency and detection limits of toxic metallic elements. Zheng et al Zheng et al (2017) experimental parameters and obtained the optimized design parameters for their CAM system. In this study, we employed spark emission spectroscopy to quantify toxic metallic elements.…”

Analysis of Crystalline Silica Aerosol Using Portable Raman Spectrometry: Feasibility of Near Real-Time Measurement

“…Although in situ measurements of chemical composition of suspended aerosol particles using this technique have been reported in several studies, − the detection limits are too high (greater than 1 mg/m 3 ) to be practically useful for trace-level measurements of atmospheric or workplace aerosols. Aerosol microconcentration, wherein airborne particles are deposited over a small (microscale) area of a collection substrate, has proven to be a useful technique for improving the measurement sensitivity for aerosol characterization using microscale spectroscopy, such as laser-induced breakdown spectroscopy, spark emission spectroscopy, − glow discharge optical emission spectroscopy, and quantum cascade laser-based infrared spectroscopy . The objective of this study was to assess the effectiveness of various aerosol microconcentration techniques for trace measurement of airborne RCS using a “field-portable” Raman spectrometer.…”