[en] This paper presents a method of x-ray fluorescence analysis (XFA) for determining argon in thin films of SiO₂. The argon concentration is calculated on the assumption that the argon is uniformly distributed over the thickness. The approach described can be used in XFA for thin layers containing elements for which reliable standards cannot be prepared as thin coatings with known surface density. This applies particularly to elements such as Br, I, Kr, and Xe, as well as to films of sulfur, whose surfaces are not smooth and even