Quantitative microanalysis of cristobalite by X-ray powder diffraction

A method for the quantitative X-ray diffraction analysis of microgram amounts of cristobalite is presented. Dust samples (1–2 mg) distributed on Nuclepore membrane filters are placed upon a silver membrane filter in a rotating sample holder. The diffraction pattern intensities of the silver filter are used to correct for absorption and for long-term instrumental drift. The detection limit is 10 μg with an accuracy of ± 10% at the 0.3 mg level.