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X-RAY ANALYSIS OF AIRBORNE ASBESTOS. INTERIM REPORT: SAMPLE PREPARATION
Citation:
Fatemi, M., E. Johnson, R. Whitlock, L. Birks, AND J. Gilfrich. X-RAY ANALYSIS OF AIRBORNE ASBESTOS. INTERIM REPORT: SAMPLE PREPARATION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-77/062.
Description:
A measurement technique, suitable for submicrogram quantities of asbestos, using a combination of fiber alignment and x-ray diffraction was previously introduced. The x-ray measurement of aligned fibers is a straightforward operation. However, it has since been found that the sample preparation itself depends on several parameters which need critical control. The composition of the alignment medium is established as 10-20 ppm (W/V) of parlodion (cellulose nitrate) in distilled amyl acetate. The effect of filter pore-size has been shown to be more significant than previously thought. Fiber losses in the range of 50-80% of total mass are not unlikely, depending on the fiber size distribution. Similarly, ultrasonification has been shown to affect fiber size distribution and subsequent fiber retention by filters. Ambient relative humidity suitable for alignment of single drops has been established to be in the range of 35% to 45% at 22C to 20C, respectively. Parameters involved in radio frequency ashing of filters are also discussed. It is shown that ashing quality and subsequent dispersion depends on the filter membrane, and improves as this concentration is increased.