Development of SRMs 295x and 296x, Respirable Crystalline Silica on Filter

Standard Reference Material (SRM®) series 2951 to 2958 (5 μg to 1000 μg) Respirable Alpha Quartz on Filter and SRM series 2961 to 2967 (5 μg to 1000 μg) Respirable Cristobalite on Filter were prepared gravimetrically by depositing SRM 1878a Respirable Alpha Quartz and SRM 1879a Respirable Cristobalite on filters, respectively. These new SRMs are developed to assure the quality of respirable crystalline silica measurements using x-ray diffraction and infrared spectrometry around the regulatory limits that are enforced by the Occupational Safety and Health Administration (OSHA). The mass of silica determined by highly sensitive, but non-polymorph-specific, inductively coupled plasma optical emission spectrometry (ICP-OES) was successfully used to calculate the mass of polymorphspecific crystalline silica on filter after all sources of Si on the new SRMs were carefully analyzed. The certified values of alpha quartz in SRMs 2951 to 2958 and cristobalite in SRMs 2961 to 2967, respectively, were established from the gravimetric preparation values and the spectrometric measurement values.