Nevertheless, further samples (with wider reference value concentrations) should improve the robustness of the calibration and validation results. Further analytes could also be analysed by collecting more various samples and analysing them.
The key point for an efficient application is that a suitable range of products containing a large range of element contents has to be available to obtain robust calibrations.
The setting up of the calibration standards is a really important step during implementation of XRF for routine analyses.