Research On The Theoretical Calculation And Application Of MLD Coefficient In XRF Analysis

In X-ray fluorescence analysis, fused bead method is a common practice for analyzing chemical composition of inorganic materials. In the preparation of unknown sample beads, usually we should ensure the ratio by mass of flux to the sample(dilution ratio) are equal to the dilution ratio of the calibration samples which make the calibration curve, in order to make the corresponding X-ray fluorescence intensity is comparable. If we do dilution ratio correction for the intensity of the X-ray fluorescence, there is no need to stirct control to the unknown sample dilution ratio, which can significantly improve the analyzing efficiency. The purpose of this paper is establish a complete set of MLD coefficient calculation method according to the dilution ratio correction coefficient′(coefficient of MLD) definition, and using software to compile a set of MLD coefficient calculation program and realize the automatic calculation of the MLD coefficient.MLD coefficient is the ratio of total mass absorption coefficient of flux to the total mass absorption of sample. According to the definition, from X-ray tube spectrum′ short wave limit to the analyte element′ the absorption limit, every 0.002 nm to take a point, using the mass absorption coefficient algorithm and typical chemical composition of sample and flux calculate the total mass absorption coefficient of the flux and the sample, their ratio is the MLD coefficient under the particular wavelength excitation, take the product of monochromatic excitation X-ray intensity and the mass absorption coefficient of element to be measured as the weight, calculated the weighted average value, namely the weighted average MLD coefficient.In order to simplify the calculation of MLD coefficient, using the concept of equivalent wavelength. There are a variety of plans to choose suitable Equivalent wavelength:(a) absorption edge +0.3k V;(b) 2/3 absorption edge;(c) the Rh target Kα line;(d) the Rh target Lα line. Using different equivalent wavelength selection plans calculated MLD coefficients of five kinds of chemical constituents of ten kinds of materials, by comparing to the experimental MLD coefficient to find the suitable paln for the analysis of the corresponding chemical composition of material.Through the reseach, the calculation method and program of MLD coefficient for dilution ratio correction are established. The program can calculate the corresponding MLD coefficient if the measurement conditions of the elements and the typical chemical components of the sample are input. Using the program and the method of dilution ratio calculation, five chemical compositions(silicon, ferrum, aluminum, calcium, magnesium) of the refractory, cement and raw materials were analyzed, the feasibility of the program is verified. Through the study of Samples of different chemical compositions(the refractory, cement and raw materials), the suitable equivalent wavelength plan to calculate MLD efficient for each analyte element(silicon, ferrum, aluminum, calcium, magnesium) of these samples is found out. Namly, when calculating the MLD coefficient, the equivalent wavelength of magnesium, aluminum and silicon is Rh Lα(λ=0.460nm); The equivalent wavelength of calcium and ferrum is the 2/3 Kα absorption edges.