AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Influence of Electrode and Carrier Gas Characteristics on the Measurement of Elemental Concentration of Aerosols Using Spark Plasma Spectroscopy
Prasoon Diwakar, PRAMOD KULKARNI, Centers for Disease Control and Prevention, NIOSH
Abstract Number: 605 Working Group: Instrumentation and Methods
Abstract We have recently reported on the development of an aerosol preconcentration method that allows near-real-time measurement of elemental concentration of aerosols using spark plasma spectroscopy (J. Anal. At. Spectrom., DOI:10.1039/C2JA30025G) at absolute mass detection limits in the range of 11 pg-5 ng. The method involves collection of aerosol on a tip of 500 µm tungsten electrode, followed by ablation and atomization by a pulsed spark plasma and detection of emission spectra. This study further probes the effect of electrode size (100, 250, 500 µm) and material (W, Pt, Rh), and the type of carrier gas (He, N, Ar) on the sensitivity and detection limits of our method. Results suggest that the smaller diameter electrodes result in a greater analyte signal enhancement; the 100 µm electrode gave an enhancement of a factor of 2 over 250 µm electrode. Carrier gas perhaps had the strongest influence on the signal. For a 100 µm electrode, the absolute analyte signal intensity increased by a factor of 2.5, 4, and 10, compared to that in air, when the carrier gas was He, N, and Ar respectively. Ar resulted in maximum enhancement in signal intensity (factor of 10) resulting in improved sensitivity of the technique; however also resulted in higher background intensity. No significant effect on signal intensity was observed for different electrode materials. Detection limits in sub-picogram levels can be achieved for many elements by employing 100 µm electrode in Ar carrier gas. Measurements of electron density and excitation temperature are presented and atomic emission enhancement mechanisms are discussed.