Examples of Heterogeneous Materials, including plated, painted dirty, “buried” or mixed substances. XRF spectrometry is generally considered a “surface” analysis. However, X-Rays can penetrate the surface to some extent, depending on the nature of the material. Light elements (e.g., C,H,N,O) are weak absorbers of the radiation and allow for deeper penetration of X-Rays compared to transition metals and elements with higher atomic numbers. If a material is not homogeneous (and if the analysis is being carried out non-destructively on an item), the XRF result will be a weighted average of the composition of the surface and interior. Similar averaging is seen for particles or components that are placed in a side-by-side arrangement. Some examples are shown below.
Partial Shielding of a Tin Disk by a 0.3 mm-Thick Copper Sheet
Partial Shielding of a Tin Disk by a 1/4″-Thick Pad of Paper
Partial Shielding of a Tin Disk by a 0.81 mm-Thick Aluminum Sheet
Partial Shielding of a Cadmium Coin by an Acrylic Holder
XRF Analysis of a Tin Disk in a 2-miL Polyethylene Bag
XRF Analysis of Galvanized Steel
XRF Analysis of Nickel-Plated Vanadium Steel
XRF Analysis of a Gold-Plated Tungsten Alloy
Plastic versus Glass: How Filtering can Affect Ratio of La to Lb Lines
Pieces of Pure Zinc and Copper are Seen as Brass by XRF Analyzer