Detection of gaseous and particulate fluorides by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) was evaluated for the detection of gaseous and particulate fluorides in air and other gas mixtures. Analytical figures of merit were compared in pure air, pure He, air-He mixtures, and air with a He sheat flow. Particulate samples were also collected on filters and subsequently detected. It was demonstrated that SF₆ is a suitable surrogate for calibration and optimization for the detection of HF in air. For gaseous F in air, limits of detection obtained were 40 mg/m³ for the direct measurement in air and 5 mg/m³ when the air sample was sheathed in He. For particulate F in air, limits of detection were 9 mg/m³ for direct measurement in air and 0.5 mg/m³ using He sheath flow. When the particulates were preconcentrated by collection on a filter and subsequently analyzed, the limit of detection for F was improved to 5 μg/m³ for a 10-min sampling time at 10 L/min flow rate using subsequent LIBS measurements in pure He.