What Elements Are Detectable by XRF?

X-ray fluorescence analysis (XRF) is one of the most common methods of elemental analysis of materials and is used in many areas of industry and scientific research. One of the reasons for the popularity of this method is its versatility, which allows it to be used to solve a wide range of problems.

The main limitation of XRF is that XRF cannot be used to determine the concentrations of the elements of the first two periods of the periodic table (elements with atomic number Z < 11) and therefore, for example, XRF is not applicable to determine the proportion of carbon in steels. This is primarily due to the low fluorescence yield and strong absorption of low-energy X-rays in air. The remaining elements of the periodic table, up to and including uranium, are within the detection range of X-ray fluorescence analysis, and their concentrations in the sample can be determined with an accuracy of fractions of a percent. XRF is especially sensitive to heavy elements, and allows you to determine the presence in the sample of such elements as lead, chromium or mercury at the level of 1 ppm. Also, despite the impossibility of analyzing the oxygen concentration in the sample, the XRF method is applicable in calculating the concentrations of metal oxides.

However, it should be noted that the above detection range may vary depending on the specific model of the spectrometer. First of all, this concerns light elements. As mentioned above, low-energy X-ray radiation is more strongly absorbed in air, which leads to a deterioration in the sensitivity of the method when determining the concentrations of elements such as aluminum, silicon and magnesium. Therefore, not all models of XRF spectrometers are suitable for this task. For maximum accuracy in determining the concentrations of light elements, modern models of benchtop XRF spectrometers have the function of purging the measurement chamber with helium to reduce absorption. One should also pay attention to the maximum voltage of the X-ray tube of the spectrometer, because for the analysis of medium elements (Z < 40) a voltage of 30 kV is sufficient, while for the analysis of heavy elements a higher tube voltage is required.

Thus, X-ray fluorescence analysis is applicable to determine the concentrations of elements from sodium (Z = 11) to uranium (Z = 92), but when purchasing an Elvatech’s portable XRF analyzer, it is worth consulting with the supplier and making sure that a specific spectrometer model is suitable for solving the task.

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