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Procedure for calibration of a portable, real-time beryllium aerosol monitor based on laser-induced breakdown spectroscopy
Abstract
The toxic metal beryllium is finding applications in a growing number of workplaces, potentially affecting an expanding segment of the work force. The current, accepted method for determining employee exposure to airborne beryllium is NIOSH Method 7300, "Elements by ICP." The most objectionable disadvantage to NIOSH Method 7300 is that a waiting period of approximately 8 hours is required to obtain results. Laser-induced Breakdown Spectroscopy (LIBS), sometimes called Laser-induced Plasma Spectroscopy (LIPS), is an analytical method whereby atmospheric components and contaminants may be analyzed in real-time or near real-time directly in the workplace. A transportable beryllium air monitor system based on LIBS has been developed at the Los Alamos National Laboratory (LANL). Airborne atoms, molecules, small particles, and the surface atoms or molecules from large particles entering the monitor are vaporized and ionized by a laser pulse. The LIBS instrument detector is tuned to the primary characteristic spectral emission line for beryllium. Onboard calibration is provided by a built-in hollow-cathode lamp (HCL). This HCL is the same kind as is used in atomic absorption spectroscopy (AAS). The intensity of the beryllium spectral line emitted from the LIBS plasma can be used to measure beryllium concentrations in air. An experimental protocol was developed to determine a correlation with 95% confidence between response of the portable instrument for real-time laser-induced breakdown spectroscopy (LIBS monitor) and results of the standard NIOSH Method 7300. Simultaneous samples were taken of a standard aerosol containing known amounts of a high purity, well-characterized beryllium metal particulate aerosol. Aerosols were generated with a Lovelace nebulizer attached to a mixing chamber of approximately 3 L with three sampling ports. The center port was attached to the LIBS monitor and the two outer ports were attached to NIOSH method 7300 filters. The LIBS exhaust was also sampled by the NIOSH method. Instrument failure prevented obtaining any data for the calibration procedure. Recommended modifications to improve reliability of the LIBS monitor are discussed. The calibration protocol is ready for further correlation experiments once the LIBS has been repaired.
Description
Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references (leaves 27-31).
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Citation
Killough, David Thomas (2000). Procedure for calibration of a portable, real-time beryllium aerosol monitor based on laser-induced breakdown spectroscopy. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2000 -THESIS -K49.
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