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Consideration of kaolinite interference correction for quartz measurements in coal mine dust.

Authors
Lee-T; Chisholm-WP; Kashon-M; Key-Schwartz-RJ; Harper-M
Source
J Occup Environ Hyg 2013 Aug; 10(8):425-434
NIOSHTIC No.
20042791
Abstract
Kaolinite interferes with the infrared analysis of quartz. Improper correction can cause over- or underestimation of silica concentration. The standard sampling method for quartz in coal mine dust is size selective, and, since infrared spectrometry is sensitive to particle size, it is intuitively better to use the same size fractions for quantification of quartz and kaolinite. Standard infrared spectrometric methods for quartz measurement in coal mine dust correct interference from the kaolinite, but they do not specify a particle size for the material used for correction. This study compares calibration curves using as-received and respirable size fractions of nine different examples of kaolinite in the different correction methods from the National Institute for Occupational Safety and Health Manual of Analytical Methods (NMAM) 7603 and the Mine Safety and Health Administration (MSHA) P-7. Four kaolinites showed significant differences between calibration curves with as-received and respirable size fractions for NMAM 7603 and seven for MSHA P-7. The quartz mass measured in 48 samples spiked with respirable fraction silica and kaolinite ranged between 0.28 and 23% (NMAM 7603) and 0.18 and 26% (MSHA P-7) of the expected applied mass when the kaolinite interference was corrected with respirable size fraction kaolinite. This is termed "deviation," not bias, because the applied mass is also subject to unknown variance. Generally, the deviations in the spiked samples are larger when corrected with the as-received size fraction of kaolinite than with the respirable size fraction. Results indicate that if a kaolinite correction with reference material of respirable size fraction is applied in current standard methods for quartz measurement in coal mine dust, the quartz result would be somewhat closer to the true exposure, although the actual mass difference would be small. Most kinds of kaolinite can be used for laboratory calibration, but preferably, the size fraction should be the same as the coal dust being collected.
Keywords
Analytical-processes; Silica-dusts; Coal-mining; Underground-mining; Dusts; Dust-particles; Particulate-dust; Particulates; Respiratory-system-disorders; Respiration; Respiratory-irritants; Pulmonary-function; Pulmonary-system; Pulmonary-system-disorders; Author Keywords: coal dust; FTIR; kaolinite; NMAM 7603; P-7; quartz; silica
Contact
Taekhee Lee, NIOSH, 1095 Willowdale Road, M/S 3030, Morgantown, WV 26505
CODEN
JOEHA2
CAS No.
14808-60-7; 7631-86-9
Publication Date
20130801
Document Type
Journal Article
Email Address
fwc8@cdc.gov
Fiscal Year
2013
NTIS Accession No.
NTIS Price
Identifying No.
B20130718
Issue of Publication
8
ISSN
1545-9624
NIOSH Division
HELD; DART
Priority Area
Construction; Mining
Source Name
Journal of Occupational and Environmental Hygiene
State
WV; OH
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