Page:NIOSH Manual of Analytical Methods - 7602.pdf/6

 Silica, Crystalline by IR: Method 7602, Issue 3, dated 15 March 2003 - Page 6 of 6 APPENDIX B: DETERM INATION OF QUART Z IN BULK SAMPLES Additional equipment needed:

Drying oven W ilks Mini-Press, or other pellet press Min-U-Sil 30

1. Ho m oge nize the sam ple if necessary (e.g., by grinding using a large m ortar and pes tle) and dry it (e.g., in a vacuum oven at 110 °C for 2-4 hours). 2. Using a small aluminum weighing boat and a six-place analytical balance, weigh out 0.1 to 1 mg of the sample. The amount weighed out should contain a quantity of quartz which will produce an absorbance which is measurable, but which is not greater than about 0.9. NOTE: The weighed amount of sample and the amount of KBr (step 3) are specified for the W ilks Minipress, which pro duces pellets a pproxim ate ly 8 m m in diam ete r. Adju st th e am ounts appropriately if another pellet press is used. 3. 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. Calibration and Q uality Control. a. Prepare calibration standards, using dry Min-U-Sil 30, in exactly the same m anner as samples (steps 2-5) and plot peak a bsorbance vs. m icrogram s S iO 2. b. Analyze bulk sample of known quartz content and prepare a control chart of recovery for us e with subsequent analyses.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition