SILICA, CR YST ALLINE , by XRD: M ETH OD 7500, Issue 4, dated 1 5 Ma rch 2003 - Page 2 of 9
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 (NIST), Gaithersburg, MD 20899; ww w.nist.gov. b. Tridymite* (210-75-0043) available from U.S. Geological Survey, Box 25046, MS 973, Denver, CO 80225. 2. 2-Propanol*, reagent grade. 3. De siccant. 4. Glue or tape for securing Ag filters to XRD holders. 5. Optional: tetrahydrofuran (THF)* (if LTA or m uffle furnace are una vailable). 6. 1.5 % parlodion solution. (Dissolve 1.5 g of parlodion* in isopentyl acetate* and dilute to 100 m L with isope ntyl acetate.) 7. Op tional (if ca lcite presen t): 25% v/v concentrated hydrochloric acid* (ACS reagent grade) in distilled water and 25-mm filters of PVC or cellulose ester with pore size of 1 :m or less.
See SPECIAL PRECAUTIONS.
1. Sam pler: a. Filter: Polyvinyl chloride (PVC) filter, 37mm , 5.0-:m pore size su ppo rted w ith back up pad in a two-piece, 37-m m cassette filter ho lder (preferably, conductive) held together by tape or cellulose shrink band. NOTE: Chec k eac h new lot of PVC filters by analyzing one or m ore by this method. For example, Gelman VM-1 filters (all lots) were found to be unacceptable because of high ash and background. If THF is used, chec k fo r com plete dissolution by dissolving a blank PVC filter and following steps 5c throu gh 8 . b. Cyclone: 10-m m nylon, H iggins-Dew ell (HD ), Alum inum (Al), or e quiva lent [11 ]. 2. Area air sampler: PVC m embrane filter, 37mm diameter, 5-:m pore size; three-piece filter cassette. 3. Sam pling pumps with flexible connecting tubing , capable of the following flow rates : nylon cyclone , 1.7 L/m in; HD cyclon e, 2.2 L/m in; A l cyclone, 2.5 L/m in; and bulk sampler, 3 L/min. 4. Silver mem brane filters, 25-mm diame ter, 0.45-µm pore size, available from Sterlitech Corp., 22027 70 th Ave S, Kent, W A 980321911; www.sterlitech.com. 5. X-ray powder diffractometer (XRD ) equipped with copp er targ et X-ray tube, gra phite m onoch rom ator, and scintillation detector. 6. Reference specimen (m ica, Arkansas stone, or oth er sta ble sta nda rd) for data normalization. 7. Low-temperature radio-frequency plasma asher (LTA) or m uffle furnace, or ultrasonic bath ($150 W ), for filter preparation. 8. Vacuu m filtration asse m bly and side-arm vacuum flask with a 25-m m filter holder. 9. Sieve, 10-:m, for wet sieving. 10. An alytic al balance (0 .00 1 m g); m agnetic stirrer with th erm ally insulate d top; ultrasonic bath or probe; volumetric pipettes and flask s; P yrex crucibles with covers (m uffle furnace); 40-m L wide-m outh or 50-m L centrifuge tubes (T HF m ethod); desiccator; reagent bottles with ground glass stoppers; drying oven; polyethylene wash bottle. 11. Explosion-resistant hot plate. 12. Teflon sheet, 0.3 to 1 mm thick.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
