Page:NIOSH Manual of Analytical Methods - 7500.pdf/8

 SILICA, CR YST ALLINE, by XRD: M ETH OD 7500, Issue 4, dated 1 5 Ma rch 2003 - Page 8 of 9 [14] [15] [16] [17] [18]

[19] [20] [21]

Talvitie NA [1951]. Determination of q uartz in presence of silicates using phosphoric acid. Anal Chem 23 (4). Hurst VJ, Schroeder PA and Styron RW [1997]. Accurate quantification of quartz and other phases by powder X-ray diffractometry. Anal Chem Acta 337:233-252. W illiams D D [1959]. Direct quantitative diffractometric analysis. Anal Chem 31:184 1. Ab ell MT, Dollberg D D, Crable JV [1981]. Quantita tive analysis of dust samples from occupational environments using computer automated X-ray diffraction. Advances in X-Ray Analysis 24:37. Ab ell MT, Dollberg DD, Lange BA, Hornung RW, Haartz JC [1981]. Absorption corrections in X-ray diffraction dust analyses: procedures employing silver filters. Electron Microscopy and X-Ray Application s, V. 2, p. 115, Ann Arbor Science P ublishers, Inc. Dollberg DD, Abell M T, Lange BA [1 980]. O ccupatio nal health analytic al chem istry: quantitation using x-ray powder diffraction. ACS Symposium Series, No. 120, 43. Altree-W illiams S, Lee J, Mezin NV. Qualitative X-ra y diffractometry on respirable dust collected on nuclepore filters. Ann Occup Health Hyg 20:109. Leroux J, Po wers C [1970]. Direct X-ray diffraction quantitative analysis of quartz in industrial dust film s depos ited on silver m em brane filters. Occ up He alth Rev 21:26.

METHOD REVISED BY: Rosa Key-Schwartz, Ph.D., Dawn Ramsey, M.S., and Paul Schlecht, NIOSH/DART.

APPENDIX: INTERFERENCES Interferences include barite, micas (muscovite, biotite), potash, feldspars (m icrocline, plagioclase), montm orillonite, sillimanite, zircon, graphite, iron carbide, clinoferrosillite, wollastonite, sanidine, leucite, orthoclase, and lead sulfide. The patterns for three forms of aluminum phosphate [JCPDS 10-423, 11-500, 20-44] are practically identical to those of quartz, cristobalite and tridymite, respectively. The quartz secondary and cristobalite primary peaks are c lose; cristob alite secon dary peak is overlapped b y a qua rtz peak; tridymite, if present in sufficient quantity, will interfere with all of the main (primary, secondary and tertiary) quartz and cristobalite peaks. Silver chloride, if present on the silver filter, interferes slightly with the primary quartz peak. Many of these interferences occur in the presence of quartz; however, in a study of samples collected in 11 different industries, Altree-W illiams [20] found no significant interferences. The pre sence of ele m ents s uch as iro n can res ult in appreciable X -ray fluorescence which leads to high background intensity. A diffracted-beam m onochromator will minimize this problem. If calcite is present, loss of quartz will occur when samples are ashed in a muffle furnace. See SAMPLE PREPAR ATION (step 5.b) for procedure to remove calcite. If interferences with the primary silica peak are present, use a less sensitive peak. W hen overlaps are not severe, a sm aller receiving slit or chromium radiation may be used; however, a new calibration curve will be necessary.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition