Page:NIOSH Manual of Analytical Methods - Chapter R.pdf/10

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 ${\ce {SiO2}}$ in 2-propanol (deposited on silver membrane filter)	suspensions of ${\ce {SiO2}}$ in 2-propanol (deposited on silver membrane filter)	suspensions of ${\ce {SiO2}}$ 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 ${\overline {CV}}$

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.