Toward elemental analysis of ambient single particles using electrodynamic balance and laser-induced breakdown spectroscopy

Abstract

In this article, we present a novel method for the elemental analysis of airborne aerosol particles using electrodynamic balance (EDB) trapping followed by laser-induced breakdown spectroscopy. The setup consists of a newly designed corona-based aerosol charger, doublering electrodynamic balance trap and optical arrangement for the spectroscopy. Experimental laboratory measurements using the method show that the minimum particle size for successful analysis is 1 mm in diameter, and the minimum airborne concentration is of the order of 1 particle/cm 3. In addition to the method, we will present results on the charging efficiency of the developed charger and novel stability analysis of the EDB at the charge region. The results from the stability analysis will ease the way toward analyzing submicron particles with the technique.

Elemental analysis of single ambient aerosol particles using laser-induced breakdown spectroscopy

“…After the charger, the aerosol was dried and introduced into another CPC (3750, TSI Inc.) through a DMA (3085, TSI Inc.). When scanning voltages with the DMA, the number concentration measured by the CPC is directly proportional to the density function of the particle charge , as demonstrated earlier 27 .…”

“…The expression includes parameters and which describe the drag force and the electric force exerted to the particle, respectively. In the parametrization, ρ is the density of the particle, is the distance from the edge of an electrode into the symmetry axis and is a geometric constant describing the slope of the oscillating electric field 27 . The parametrization leads to a dimensionless equation from which stability areas with respect to and can be numerically calculated 36 .…”

“…1 b, the particle diameter after the amplification has a median at about 3 µm. After the size amplification, the aerosol flows through a unipolar corona-discharge based aerosol charger, presented in more detail in earlier research 27 . As the particles are size amplified, the powerful electric field in the charger causes them to acquire a high electrical charge 32 (Figs.…”

“…Because of the low density of the carrier gas, the matrix effects are significantly lower than with the more traditional solid substrates 24 , 25 . However, as LIBS analysis relies on plasma emission induced by a highly focused laser pulse, either the aerosol particle concentration has to be very high 26 or the particles have to be focused 27 – 29 . With state-of-the art sheath air focusing and timed ablation, sampling rates of tens of particles/minute for single particles are achievable with concentrations above c.a.…”

Review of In-Situ Online LIBS Detection in the Atmospheric Environment

“…Heikkilä et al studied single-particle elemental analysis of airborne aerosols by combining EDB trapping with the LIBS technique. 58 A coronabased aerosol charger, double-ring EDB trap were imposed in the LIBS setup to increase the detection efficiency and reduce the LOD.…”