X-ray fluorescence (XRF) technology is a fast, highly accurate method for analyzing the soil removal capability of cleaning products such as vacuum cleaners and carpet extractors.
In basic terms, the XRF hand-held instrument emits energy and excites the atoms of a target element. The energy generated in response is called X-ray fluorescence, which can be detected and measured by the device. Each atomic element has its own unique energy signature. The XRF instrument measures each energy signature to determine the presence and concentration of various soil elements based upon this unique signature.
XRF, in this application, was developed in a collaboration between private industry, the Carpet & Rug Institute and NASA.
Source: Georgia Institute of Technology”