Why does XRF analysis report elements as oxides?

Answer 1

There is an XRF method used for rocks and minerals that involves making a glass disc by fusing the stuff being analyzed in the presence of air at high temperature in a platinum crucible with lithium borates. This process converts any free metals and salts such as carbonates, sulfates and sulfides to oxides. So the results are shown for the oxide *end products* of the analytical method.

This method gives better accuracy and precision than just throwing the mineral in a bag and analyzing it directly. But some XRF methods do not involve fusion, in which case the readout is estimated wt% or ppm of the total metal, not the oxide. In either case, the *relative* amounts of metals should be the same, as long as you don't have something like Mercury metal that evaporates when you heat it.

Answer 2

XRF analysis typically reports elements as oxides because during the analysis process, the elements in the sample combine with oxygen from the environment to form oxides. This makes it easier to detect and measure the elements accurately using the XRF technique. Additionally, element oxides have distinct X-ray signatures that can be used to identify and quantify different elements in the sample.