A new X-ray diffraction method for the quantitative analysis of free silica in the airborne dust in working environment.

Abstract

A simple and rapid X-ray diffraction method, employing a metal plate as a substrate standard for X-ray absorption correction, was developed for the determination of the quantity of free silica in airborne dust of the working en-vironment. A membrane filter or a Nuclepore filter, on which airborne dust in-cluding quartz was collected, is directly mounted on a zinc plate as a substrate standard. The X-ray absorption of the sample is corrected by the attenuation of the X-ray diffraction beam from the metal substrate standard. The lower and higher limit of the sample weight qualified by this method and the accuracy are both similar to those of the NIOSH method, which uses a silver membrane filter as a substrate standard. The advantages of the present method are reduction in the cost of analysis, because only a membrance filter is used together with a zinc plate, and avoiding the troublesome processes of sample preparation, such as ashing of the collection filter, ultrasonic treatment, and redeposition of the dust sample on a silver membrane filter, consequently excluding artificial effects. It is concluded that the present method is suitable for the quantitative analysis of microgram free silica in airborne dust in the working environment.