Page:NIOSH Manual of Analytical Methods - 7603.pdf/1

 QUARTZ in coal mine dust, by IR (redeposition) SiO2

MW: 60.08

METHOD: 7603, Issue 3

CAS: 14808-60-7

RTECS: VV7330000

EVALUATION: UNRATED

OSHA : quartz (respirable): 10 mg/m3 / (%SiO2 + 2) NIOSH: 0.05 mg/m3 (suspect carcinogen) ACGIH: 0.1 mg/m3

PROPERTIES:

7603

Issue 1: 15 May 1989 Issue 3: 15 March 2003

solid; d 2.65 g/cm3 ; crystalline transformations: quartz to tridymite @ 867 °C: trydymite to crystobalite @ 1470 °C; "quartz to $-quartz @ 573 °C

SYNONYMS: free crystalline silica; silicon dioxide SAMPLING SAMPLER:

CYCLONE + PREWEIGHED FILTER (10-mm cyclone, nylon or Higgins-Dewell (HD), and PVC filter, 37-mm, 5-µm)
 * see sampling section

FLOW RATE: HD cyclone: 2.2 L/min nylon cyclone: 1.7 L/min VOL-MIN: -MAX:

300 L @ 0.1 mg/m3 1000 L

SHIPMENT:

Routine

MEASUREMENT TECHNIQUE:

INFRARED ABSORPTION SPECTROPHOTOMETRY (IR)

ANALYTE:

Quartz

WEIGH:

Dust cassette

ASH:

Muffle furnace or RF plasma asher

REDEPOSIT:

0.45-µm acrylic copolymer membrane filter

IR:

Scan, 1000 to 650 cm-1, absorbance mode with blank filter in reference beam

SAMPLE STABILITY:

Stable

BLANKS:

2 to 10 field blanks per set

CALIBRATION:

NIST SRM 1878a suspension in 2-propanol

Rrequired for OSHA standard calculations; area respirable or settled dust

RANGE:

30 to 250 µg quartz per sample [1]

ESTIMATED LOD:

10 µg quartz per sample [1]

PRECISION ( þ r ):

0.098 @ 100 to 500 µg per sample (varies with sample matrix) [1]

BULK SAMPLE:

ACCURACY RANGE STUDIED:

25 to 160 µg/sample [1] (2 mg quartz/m3 atmosphere)

BIAS:

Unknown

OVERALL PRECISION (Ö r T ): 0.13 to 0.22 (varies with sample loading and matrix ACCURACY:

±25.6 to 43.4%

APPLICABILITY: The working range is 0.03 to 0.25 mg/m3 for a 1000-L sample. The method was specifically developed for respirable coal mine dust samples [1]. The precisions (þr & þrT ) stated above are based on ruggedization data [2]. IR is useful for a simple matrix like coal dust where the interference can be removed. See also discussion of crystalline silica in Chapter R of this volume [3]. INTERFERENCES: Calcite is used as a dusting agent in coal mines and interferes by reacting with quartz during muffle furnace treatment resulting in low quartz assay. Kaolinite is sometimes present in coal dust and interferes by absorbing radiation at the quartz analytical wavelength of 800 cm-1. These interferences are corrected by procedures given in this method. Muscovite does not interfere. Cristobalite and tridymite have absorbance peaks at 800 cm-1. Cristobalite and tridymite have not been detected in coal mine dust. OTHER METHODS: This is similar to MSHA P-7 which was collaboratively tested [2,4]. Quartz can also be determined by Methods 7500 (XRD) and 7602 (IR). XRD can distinguish the three silica polymorphs and silica interferences can be eliminated by phosphoric acid treatment. Crystalline silica can also be determined by visible absorption spectrophotometry (e.g., Method 7601), but polymorphs cannot be distinguished. Visible absorption methods also have larger laboratory-to-laboratory variability than XRD and IR methods and therefore are recommended for research use only [5].

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition