AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Corona-assisted Microwave Plasma Spectroscopy for Spectrochemical Analysis of Aerosols
PRAMOD KULKARNI, Philip Efthimion, Centers for Disease Control and Prevention, NIOSH
Abstract Number: 608 Working Group: Instrumentation and Methods
Abstract A new approach employing microwave-induced plasma assisted by localized non-thermal dc corona has been developed for near-real-time elemental analysis of aerosols. The technique involves preconcentration of aerosols for a predetermined period of time on the tip of a microelectrode located at the center of a reentrant-type microwave cavity, followed by introduction of pulsed microwaves (2.45 GHz, 3 kW). The presence of the electrode in the cavity concentrates the electromagnetic field on its tip, subsequently leading to formation of microwave-induced plasma, which ablates and atomizes the particulate matter deposited on the microelectrode tip. The resulting atomic emissions are recorded using a broadband optical spectrometer for element identification and quantification. To improve the reproducibility of the microwave plasma, a stable dc corona is introduced on the tip of the microelectrode which provides additional seed electrons for effective coupling of microwaves. This drastically improves repeatability and stability of the plasma. Lifetime of the microwave plasma was in the range of 5-10 ms, which is orders of magnitude larger than that for laser-induced or sparks plasmas of comparable power density, and leads to significantly higher signal intensities. The system was calibrated using mobility-classified aerosols of various analytes. Sensitivity and limit of detection of the method will be presented and implications for near-real-time analysis of aerosol will be discussed.