QUANTITATIVE-DETERMINATION OF RESPIRABLE QUARTZ IN BULK SAMPLES OF ORGANOCLAY BY COMBINED AIR CLASSIFICATION X-RAY-DIFFRACTION

There are a multitude of sampling techniques and quantitative methods for respirable silica in airborne materials but no sampling techniques exist to determine respirable silica in bulk samples. In order to det ermine the respirable quartz portion in an organoclay, a scheme was de vised to employ air classification to separate the fines or respirable portion from the non-respirable or coarse portion. We chose less-than -or-equal-to 10 mum material to represent the respirable portion. The total quartz content of the organoclay was determined on the ''as-is'' bulk sample by x-ray diffraction (XRD), using standards prepared in t he laboratory and matrix matched to the organoclay being analyzed. The organoclay was then passed through an air classifier and separated in to two fractions. Both the fines (less-than-or-equal-to 10 mum organoc lay) and the coarse (> 10 mum) portions were analyzed by XRD for perce ntage of crystalline silica. Preliminary results appear encouraging in that air classification can separate respirable material and XRD is c apable of measuring quartz quantitatively to the < 1% level.