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New approach for near-real-time measurement of elemental composition of aerosol using laser-induced breakdown spectroscopy.

Authors
Diwakar-P; Kulkarni-PS; Birch-ME
Source
Aerosol Sci Tech 2012 Mar; 46(3):316-332
NIOSHTIC No.
20039872
Abstract
A new approach has been developed for making near-real-time measurement of elemental composition of aerosols using plasma spectroscopy. The method allows preconcentration of miniscule particle mass (pg to ng) directly from the sampled aerosol stream through electrostatic deposition of charged particles (30-900 nm) onto a flat-tip microneedle electrode. The collected material is subsequently ablated from the electrode and monitored by laser induced breakdown spectroscopy. Atomic emission spectra were collected using a broadband spectrometer with a wavelength range of 200-980 nm. A single-sensor delay time of 1.3 micros was used in the spectrometer for all elements to allow simultaneous measurement of multiple elements. The system was calibrated for various elements including Cd, Cr, Cu, Mn, Na, and Ti. The absolute mass detection limits for these elements were experimentally determined and found to be in the range of 0.018-5 ng. The electrostatic collection technique has many advantages over other substrate-based methods involving aerosol collection on a filter or its focused deposition using an aerodynamic lens. Because the particle mass is collected over a very small area that is smaller than the spatial extent of the laser-induced plasma, the entire mass is available for analysis. This considerably improves reliability of the calibration and enhances measurement accuracy and precision. Further, the aerosol collection technique involves very low pressure drop, thereby allowing higher sample flow rates with much smaller pumps - a desirable feature for portable instrumentation. Higher flow rates also make it feasible to measure trace element concentrations at part per trillion levels. Detection limits in the range of 18-670 ng m(-3) can be achieved for most of the elements studied at a flow rate of 1.5 L min (-1) with sampling times of 5 min.
Keywords
Aerosols; Spectroscopes; Spectrographic-analysis; Measurement-equipment; Nitrates; Aerosol-generators; Aerosol-particles; Aerosol-sampling; Cadmium-compounds; Chromium-compounds; Copper-compounds; Manganese-compounds; Sodium-compounds; Ammonium-compounds; Sampling; Sampling-equipment; Sampling-methods; Electrostatic-atomizers; Lasers; Electrostatic-fields; Analytical-instruments
Contact
Pramod Kulkarni, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, MS R7, Cincinnati, OH 45226, USA
CODEN
ASTYDQ
CAS No.
7440-43-9; 7440-47-3; 7440-50-8; 7439-96-5; 7647-14-5
Publication Date
20120301
Document Type
Journal Article
Email Address
PSKulkarni@cdc.gov
Fiscal Year
2012
NTIS Accession No.
NTIS Price
Identifying No.
B11122011
Issue of Publication
3
ISSN
0278-6826
NIOSH Division
DART
Priority Area
Manufacturing
Source Name
Aerosol Science and Technology
State
OH
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