Determination of quartz in bulk materials from workplace environments using X-ray diffractometry and the absorption diffraction method

A method is described for the determination of crystalline quartz in bulk materials from workplace environments as part of occupational hygiene investigations using X-ray powder diffractometry. The absorption–diffraction model was used for quantification with mass absorption coefficients for samples being experimentally determined using an absorption cell placed in front of the diffracted beam anti-scatter slit. The method was found to be reliable for samples containing from 0.5 to 100 wt.% crystalline quartz, where mass absorption coefficients did not exceed 120 cm2 g−1. Repeatability studies found that mass absorption coefficient determinations and crystalline quartz determinations were both generally within 1–2% relative standard deviation. The method was assessed for accuracy and found to be within 2% absolute when a National Institute of Standards and Technology (NIST) quartz certified reference material (SRM1879a) was analysed. The technique was compared to an internal standard procedure and a paired students t test showed that there was no significant statistical difference between the two methods at the 95% confidence level where the t value was found to be 0.40 (p > 0.05 = 0.69) and the t critical value being tcrit,0.05,29 = 2.05. The method was suitable for a variety of matrixes including those containing amorphous material and could be routinely applied to most samples of occupational interest.