National Institute for Occupational Safety and Health

“ 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. ”

“ Quantita tively transfer the weighed sample to a small mortar and grind it thoroughly. Add between 75 and 100 mg dry KBr and mix it thoroughly with the ground sample. 4. Quantita tively transfer the mixture to the pellet press. Press the pellet according to the manufacturer’s instructions. NOTE: W eighing paper and a cam el’s hair brush are helpful in m ak ing the transfer. 5. Scan the pellet from 1000 cm -1 to 600 cm -1, using a blank KBr pellet as background. Rotate the pellet 90 degrees and obtain another spectrum. Measure and record the mean peak absorbance at 798 cm -1 for the sample. 6. ”

“ If correction for kaolinite is not required, use the absorbance at 800 cm ! 1 to find the we ight of qua rtz, W q (μg) , from the calibration graph. Ca lculate the conc entra tion of silica, C (m g/m 3) , in the volum e of air sam pled, V (L) :
If percent quartz, % Q , is required, divide the weight of qu artz, W q (μg) , by the total sam ple weight, W s (μg) :
EVALUATION OF METHOD: This m eth od is based on the well-ch arac terized infrare d m etho d [1] . T his m etho d is pa rticle size d epe nde nt. A m ismatch of standards and sample particle sizes will result in an uncorrectable bias. ”

“ Although most analytical che m ists are fam iliar with the IR technique as applied to org anic analyses, mineralogical samples require additional knowledge of geology and mineralogy to correctly interpret crystal structure, matrix interferences and mineral transformation for the lab orato ry client. ”

“ 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. ”