X-ray fluorescence analysis of geological samples: exploring the effect of sample thickness on the accuracy of results.

The accuracy of the simple quantitative method of elemental XRF analysis applied to thick and thin geological samples was investigated with certified reference materials. In the case of thick samples, the intensity of the calcium signal was used as a characteristic of the sample for the dark matrix correction, as it had been found to be inversely correlated with the intensity of the silicon signal. The results of the analysis of thick samples did not depend on the sample form (pressed disc or a powder in a cup), and the absorption factors were very high. In the analysis of thin samples, the detection limits, sensitivity, and accuracy have been improved, particularly for light elements. As the absorption factors are close to unity for thin samples, there is no need for a matrix-effect correction or certified reference materials.