ELSEVIER Analytica Chimica Acta 337 (1997) 233-252 ANALYTICA CHIMICA ACTA zyxwvutsrqponm Review Accurate quantification of quartz and other phases by powder X-ray diffractometry Vernon J. Hursta’*, Paul A. Schroeder”, Robert W. Styron’ zyxwvutsrqponmlkjihgfe “ Geology Deportment, University of Georgia, Athens. GA 30602-2501. USA bMineral Resource Techno1ogie.r. Atlanta. GA. (JSA Received 30 April 1996; revised 27 August 1996: accepted 28 August 1996 zyxwvutsrqponmlkjihgfedcbaZYX Abstract The 33 parameters that affect accuracy of quantitative analysis by X-ray powder diffractometry can be grouped as (1) Instrumental or systematic, (2) Inherent properties of the analyte, or (3) Parameters related to preparation and mounting of powders. The effect of each on diffraction intensity is summarized. An optimal value or range is given for instrumental parameters. Evaluation of inherent parameters of the analyte and optimization of those related to preparation and mounting of powders are discussed. Published methods are briefly reviewed. Their reported detection limits for crystalline silica are well below what can be reliably determined in natural and industrial products if one or more critical parameters are neglected. as the size and shape of coherent diffraction domains. An addendum illustrates practical consideration of major parameters during routine analysis for quartz. Key~~~d.s: Crystalline silica; X-ray diffraction; Quantification; Fly ash; Quartz; Review 1. Introduction There is increasing interest in determining and monitoring quartz and other forms of crystalline silica in commercial and industrial bulk products which are or might yield respirable dusts. For more than a century silica has been recognized as a cause of fibrosis (silicosis) which may lead to chronic lung ailments. It is regulated in USA by the Occupational Safety and Health Administration and the Mine * Corresponding author. Safety and Health Administration for worker ex- posure to respirable dust. The National Toxicological Program lists respirable crystalline silica in three natural and industrial forms a5 “reasonably antici- pated to be carcinogenic”. A currently enforced Hazard Communication Standard requires that all products containing 0.1% or more of these three forms be labelled as “Hazardous”. This regulation poses a dilemma because the 0.1% threshold is beyond the capability of methods currently in use except when they arc restricted to a well character- ized and essentially invariant bulk material. When applied generally, they cannot be relied on to detect 0003.2670/97/$17.00 Copyright ~(‘1 1997 Elsevier Science R.V. All rights reserved PII SOOO3-2670(96)0042S-4