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

A new, low-cost approach based on the application of atmospheric radio frequency glow discharge (rf-GD) optical emission spectroscopy (OES) has been developed for near real-time measurement of multielemental concentration in airborne particulate phase. This method involves deposition of aerosol particles on the tip of a cathode in a coaxial microelectrode system, followed by ablation, atomization, and excitation of the particulate matter using the rf-GD. The resulting atomic emissions are recorded using a spectrometer for elemental identification and quantification. The glow discharge plasma in our system was characterized by measuring spatially resolved gas temperatures (378-1438 K) and electron densities (2-5 × 1014 cm-3). Spatial analysis of the spectral features showed that the excitation of the analyte occurred in the region near the collection electrode. The temporal analysis of spectral features in the rf-GD showed that the collected particles were continuously ablated; the time for complete ablation of 193 ng of sucrose particles was found to be approximately 2 s. The system was calibrated using 100 nm particles containing C, Cd, Mn, and Na, respectively. The method provides limits of detection in the range of 0.055-1.0 ng, and a measurement reproducibility of 5-28%. This study demonstrates that the rf-GD can be an excellent excitation source for the development of low-cost hand-held sensors for elemental measurement of aerosols.