Matrix Effects in Portable Spectrometers

In actual work, the samples to be measured are usually composed of a variety of elements. The elements other than the elements to be measured are generally called matrix. Because the matrix composition of the measured sample is changing (this change refers to the change of elements and the change of content), it directly affects the measurement of the characteristic X-ray intensity of the measured element. In other words, the measured element content is the same, but because the matrix composition is different, the measured characteristic X-ray intensity of the measured element is different. This is the matrix effect. The matrix effect is one of the main sources of error in X-ray fluorescence quantitative analysis.

The matrix effect is an unavoidable objective fact. Its physical essence is the change in the intensity of characteristic X-rays caused by excitation (absorption) and scattering. In addition to the element to be measured, the probability of the elements in the matrix composition close to the element to be measured causing photoelectric effect to the rays of the excitation source and the characteristic X-rays of the element to be measured is much greater than that of light elements (some common main rock-forming elements in geological samples). In other words, the absorption coefficient of these adjacent elements to the X-rays emitted by the excitation source and the characteristic X-rays of the element to be measured is much greater than that of light elements; the probability of light elements Compton scattering the rays released by the excitation source and the characteristic X-rays of the element to be measured is much greater than that of heavy elements.