Impact of muffle furnace preparation on the results of crystalline silica analysis.
A prior report demonstrated an unacceptably low level of accuracy in silica analytical testing, with a general negative bias (i.e., underreporting) although other inaccuracies included false-positive results when analyzing blank filters. The possible bias may have been due to the loss of sample during shipping and or sample preparation. We report on a follow-up study that was designed to mimic the original study, but in which sources of variability were evaluated. We found no effect on silica recoveries due to shipping and confirmed the prior study results that the muffle furnace ashing process led to low overall recoveries (49-104%), depending on the adherence to the recommended preparation method. Plasma ashing recoveries ranged from 89 to 108%. Our results suggest that muffle-furnace ashing using a crucible should be restricted. More broadly, however, muffle-furnace ashing is only one source of analytical error that contributes to the relatively poor overall performance revealed by Cox et al. Whatever the case, OSHA should ensure that its proposed requirements to improve laboratory performance will actually lead to the discovery and correction of all major sources of error by participating laboratories. This is particularly important in light of OSHA's proposed reduction in the PEL and action level proposed by OSHA.
['Lee|R J|RJ|', 'Van Orden|D R|DR|', 'Cox|L A|LA|', 'Arlauckas|S|S|', 'Kautz|R J|RJ|']
D003460:Crystallization D004784:Environmental Monitoring D004867:Equipment Design D006358:Hot Temperature D006801:Humans D017745:Incineration D019570:Inhalation Exposure D015233:Models, Statistical D016273:Occupational Exposure D016272:Occupational Health D052638:Particulate Matter D015203:Reproducibility of Results D018570:Risk Assessment D012822:Silicon Dioxide
Muffle furnace Crystalline silica Plasma ash Crucible NIOSH 7500 X-ray diffraction