TABLE 3. X-RAY DIFFRACTION SAMPLING AND ANALYTICAL METHODS FOR CRYSTALLINE SILICA.
NMAM 7500 | OSHA ID-142 | MSHA P-2 | MDHS 51 /2 | |
Silica polymorph | quartz cristobalite tridymite |
quartz cristobalite |
quartz cristobalite |
quartz |
Sampler | 10-mm nylon cyclone, 1.7 L/min Higgins-Dewell cyclone, 2.2 L/min | 10-mm nylon Dorr-Oliver cyclone, 1.7 L/min | 10-mm nylon Dorr-Oliver cyclone, 1.7 L/min | Higgins-Dewell cyclone, 1.9 L/min |
Filter | 37-mm 5-µm PVC membrane | 37-mm 5-µm PVC membrane | 37-mm 5-µm PVC membrane | 25-mm 5-µm PVC membrane |
Volume | 400-1000 L total dust < 2 mg | 408-816 L total dust < 3 mg | 400-1000 L total dust < 3 mg | ≥ 456 L total dust < 2 mg |
Filter Preparation | RF plasma asher, muffle furnace or dissolve filter in THF | dissolve filter in THF | RF plasma asher | none |
Redeposition | onto 0.45-µm silver membrane filter | onto 0.45-µm silver membrane filter | onto 0.45-µm silver membrane filter | none |
Drift Correction | silver internal standard | silver internal standard | silver internal standard | external standard e.g.: aluminum plate |
X-ray source | Cu Kα 40 kV, 35 mA |
Cu Kα 40 kV, 40 mA |
Cu Kα 50 kV, 35 mA |
Cu Kα 45 kV, 45 mA |
Calibration | suspensions of in 2-propanol (deposited on silver membrane filter) | suspensions of in 2-propanol (deposited on silver membrane filter) | suspensions of in 2-propanol (deposited on silver membrane filter) | sampling from a generated atmosphere of standard quartz dust |
Proficiency Testing | PAT | PAT | PAT | WASP |
Range (µg quartz) | 20-2000 | 50-160 (validation range) | 20-500 | 50-2000 |
LOD (µg quartz) | 5 (estimated) | 10 | 5 | 3 |
Precision* | CV = 8 % 50-200 µg | CV =10.6 % 50-160 µg | CV = 10 % @ 20-500 µg | CV = 5 % @ 50 µg |
* Precision is noted in terms of CV (coefficient of variation) for all methods for convenience of comparison. CV is equivalent to sr (relative standard deviation). In some methods, precision is noted in terms of (pooled relative standard deviation) which is equivalent to
NMAM=NIOSH Manual of Analytical Methods, OSHA=Occupational Safety and Health Administration, MSHA=Mine Safety and Health Administration, MDHS=Methods for Determination of Hazardous Substances, PVC=polyvinyl chloride, RF=radio frequency, THF=tetrahydrofuran, Cu=copper, kV=kilovolts, mA=milliamps, PAT=proficiency analytical testing, WASP=workplace analysis scheme for proficiency, LOD=limit of detection, CV = coefficient of variation.