How can we resolve possible misidentification of opal C or other materials that mimic cristobalite in the analysis of cristobalite?
One resolution of this problem requires a combined approach using a modified Talvitie chemical treatment (see description and reference in OSHA ID-142 method). In order to optimize the conditions for removal of the interferent, recovery tests using cristobalite-spiked bulk material is needed to ensure that cristobalite is not being removed along with the opal-C. This procedure is tedious and is only performed when absolutely necessary. At the OSHA SLTC, the efficient use of resources is brought about by the procedures for analyzing compliance air samples for cristobalite given in method ID-142. The type of industrial operation determines whether cristobalite is analyzed. Air samples suspected of containing cristobalite are first screened on the most intense X-ray diffraction peak (JCPDS 11-695 an undistorted cristobalite). Based on the screening, if the exposure is above the detection limit and possibly over a significant fraction of the OSHA permissible exposure limit (PEL), an attemp
