On-Line in-Situ Detection of Lead Aerosols by Plasma-Spectroscopy and Laser-Excited Atomic Fluorescence Spectroscopy

Abstract

A set-up for on-line and size-segragated detection of lead in ultrafine aerosols was developed. Lead nitrate aerosols with particle diameters between 10 and 300 nm were generated by ultrasonic nebulization of aqueous Pb(NO3)2-solutions. A differential mobility particle sizer (DMPS) was used for size-resolved mass calibration. Either a miniaturized acetylene-air-flame or a laser-induced plasma (LIP) was employed for atomization. Lead was detected with a spectrometer and a gateable, intensified CCD-camera by atomic emission spectroscopy (AES) and laser excited atomic fluorescence (LEAF). Due to the lower sensitivity, for LIP-AES no size-resolved calibration was possible and for calibration with polydisperse aerosols the detection limit for lead was found to be 155 ug m-3. With LEAF and flame atomization, a linear calibration curve was obtained with on-line detection limits of 47 ng m-3 for lead. No dependence of the detection limit on the particle diameter was observed. For LEAF with a laser-induced plasma as atom source, a correlation between the detection limit and the particle diameter was found. The detection limit increased from 55 ng m-3 for a particle diameter of 48 nm to 130 ng m-3 for a particle diameter is probably due to the incomplete atomization of larger particles in the colder periphery of the plasma.