A COMPARISON OF X-RAY DIFFRACTION AND INFRA-RED SPECTROPHOTOMETRIC METHODS FOR THE ANALYSIS OF α-QUARTZ IN AIRBORNE DUSTS *

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Abstract
The two techniques, X-ray diffraction and infra-red spectrophotometry, used routinely at the HSE Occupational Medicine and Hygiene Laboratories for the determination of α-quartz in airborne dusts, have been compared on the basis of both laboratory experimentation and the analysis of several hundred workplace-dust samples. Both methods are applied directly to dust samples in situ on the filter used for collection. For workplace-dust samples, the major problem encountered in both techniques is the presence of interfering substances. This is overcome by scaled absorbance subtraction of interfering substances in the case of infra-red spectrophotometry and by selection of an interference-free diffraction line in X-ray diffraction. After making the necessary corrections for interfering substances, the overall agreement between X-ray diffraction and infra-red spectrophotometry results on workplace samples is good, although individual results sometimes show considerable discrepancies. The performance of the two techniques in terms of detection limits and precision is similar and is acceptable for occupational hygiene survey work at the present occupational exposure limit.

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