AbstractA method is described for the direct quantitative analysis by X‐ray fluorescence spectrometry of some elements in powdered materials collected on inert filters. In order to gain a view of the general applicability of the method, the effects of the interferences due to the nature of the analytical samples were studied and verified, and a possible means of overcoming them is proposed. The principal factors that effect the interference phenomena were found to be variation of the X‐ray path into the sample due to different deposit thickness, different X‐ray beam penetration owing to sample density, and absorption and enhancement of the characteristic radiation by the combining elements. The aim of this work is to propose a method which eliminates the drawbacks due to the matrix absorption effects, whatever their origin. A better understanding of the phenomena, the mathematical treatment of the basic principles and the use of experimental artifices, allowed us to achieve optimized conditions for analysis, suitable for general routine applica