Page:NIOSH Manual of Analytical Methods - 7602.pdf/2

 Silica, Crystalline by IR: Method 7602, Issue 3, dated 15 March 2003 - Page 2 of 6 EQUIPMENT:

REAGENTS: 1. Silica Standards. a. Quartz* (SRMs 1878a, 2950, 2951, 2958) and Cristobalite* (SRMs 1879a, 2960, 2957 ), available from Standard Reference Materials Program, Rm 204, Bldg. 202, National Institute of Standards and Technology, Gaithersburg, MD 20899; ww w.nist.gov. b. Tridymite* (210-75-0043), available from U.S. Geological Survey, PO Box 25046, MS 973, Denver, CO 80225. 2. Po tas sium bro m ide (KBr), infra red quality. 3. Ethanol, 95% for cleaning sample handling equ ipm ent.* 4. Hydrochloric acid, 9% w/w.* Add 25 mL conc. HC l (37% w/w) to 70 m L with deionized water, cool, and bring to 100mL with deionized water. 5. Ca libration s tock standard, 0.5% w/w. Accurately weigh and thoroughly mix 5 g KBr (dried overnight at 110 °C) w ith 25 m g qu artz. Store in a bottle in a desiccator.

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Sam pler: a. Filter: 37-m m diame ter, 5.0-µm po re size, polyvinyl chloride filter supported with backup pad in a two-piece, 37-m m cass ette filter ho lder (preferably, conductive) held together by tape or cellulose shrink band. b. Cyclone: 10-m m nylon or Higgins-Dew ell (HD ). c. Sam pling head holder: Holder must keep the cassette, cyclone and coupler together rigidly so that air enters only at the cyclone inlet. Area air sampler: PVC m embrane filter, 37mm, 5-µm pore size in two piece filter cassette. Sample closed-faced at 3 L/min. Sam pling pumps for HD cyclone, 2.2 L/min; nylon cyclone, 1.7 L/ m in; and area sam pler, 3 L/min. Infrared spectroph otom eter; laboratory press for preparing KBr pellets; 13-mm KBr pellet die (evacua ble). Low-temperature (RF Plasma) asher and aluminum weighing pan or muffle furnace and porcelain crucibles. Mo rtar an d pe stle, 50 -m m aga te or m ullite metal microspatula; non-serrate, nonm agnetic forceps; desiccator, ca m el’s hair brush, glassine pap er. Analytical balance (0.001 mg) for preparing standards. Mem brane filtration apparatus, 37-m m.

SPE CIAL PR ECAU TIO NS: Avoid inhaling silica dust [9]. Ethanol is flamm able. Keep away from flames. Use personal protective equipment to prevent contact of acids with the skin. Concentrated acids are corrosive. SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 2. Sa m ple at 1.7 ± 5% L/m in with nylon cyclone, 2.2 ± 5% with H D c yclone, or 2.5 ± 5% with Al cyclone for a total sample size of 400 to 800 L. Do not exce ed 2 m g total dust loading on the filter. NOT E 1: Do not allow the sampler assembly to be inverted at any time when using a cyc lone. Turning the cyclone to anything more than a horizontal orientation may deposit oversized m aterial from the cyclone body onto the filter. NOT E 2: A single sampler/flow rate should be used for a give n ap plication. Sampling for both crystalline silica and c oal mine du st should be don e in accordance with the ISO/CEN/ACGIH/ASTM respirable aerosol sam pling conventio n. F low rates of 1 .7 L/m in for the Dorr-Oliver nylon cyclone and 2.2 L/min for the Higgins-Dewell cyclone have been found optimal for this purpose. Outside of co al mine dus t sam pling, the regulatory agencies currently use these flow rates with the Dorr-Oliver cyclone in the United States and the Higgins-Dew ell sampler in the United Kingdom. Though the sampling recom m endations presented in a NIOSH Criteria Document have been formally accepted by MSHA for coal mine dust sampling, the Dorr-Oliver cyclone at 2.0 L/min with 1.38 conversion factor is NIOSH Manual of Analytical Methods (NMAM), Fourth Edition