WOHL performs analysis for crystalline-free silica including quartz, cristobalite and tridymite via X-ray diffraction based on OSHA ID-142. X-ray diffraction for the determination of crystalline silica is the preferred technique for almost all samples. It is specific to each form of crystalline silica. IR analysis cannot differentiate the types of silica, and it should only be used where you have a well-defined matrix like coal dust.
WOHL uses three separate peaks for the determination of both quartz and cristobalite, and two separate peaks for the determination of tridymite. This greatly reduces the likelihood of reporting out high results due to interferences. The reporting levels (RL) are: quartz RL = 10 µg/sample, cristobalite RL = 20 µg/sample and tridymite RL = 20 µg/sample.
Respirable silica is collected on pre-weighed, 5 micron PVC filters using a cyclone capable of collecting respirable particles. There are many types of these cyclones, but the two most common are the SKC aluminum cyclone and the 10 mm nylon cyclone. The 10 mm nylon cyclones typically use two-piece, 37 mm cassettes and the aluminum cyclone typically uses three-piece, 37 mm cassettes. Refer to the manufacturer’s recommended flow rates for proper respirable sampling. Request the proper filter, two- or three-piece polystyrene cassettes, to fit your cyclone.
Silica analysis can also be performed on total dust samples using PVC filters without a cyclone. Bulk samples are not required but can be analyzed.