Laser-induced breakdown spectroscopy for toxic metal emission measurements: Experimental considerations and oxygen quenching

Monitoring efforts have shown that toxic metals represent one of the most important fractions of PM 2.5 released from thermal processing units. Existing and planned regulations establish strict limits on emissions of toxic metals from process streams. The recently developed Laser-Induced Breakdown Spectroscopy (LIBS) technique is capable of sensitive elemental analysis at relatively high data rates, capable of up to 20 Hz with sensitive intensified charge-coupled device detectors. According to the LIBS methodology, a laser-induced microplasma is generated, with peak temperatures as high as 10,000-25,000 degree C. This plasma is capable of vaporizing solid material, and promotes complete vaporization of aerosol particles up to 2-10 mu m in diameter. Molecular species are atomized by the plasma. Impacts of variable oxygen concentrations are discussed.