X-ray Fluorescence Spectrometry
is one of the widely used methods in geosciences for the determination of major and trace elements in a large variety of solid samples. This method allows the routine analysis of rocks, minerals, soils and solid synthetic materials. X-ray spectrometry has the capability to determine all elements of the Periodic table from B to U.

At the Division of Geochemistry of the GZG we routinely analyse the following:

elements (major elements as oxide wt%, traces as elemental ppm):

Our instrument a PANalytical AXIOS Advanced sequential
X-ray spectrometer. Data processing is controlled
by the SuperQ 4 software package.

The samples are prepared for measurement as glass disks. Because the surface and homogeneity of the specimen are essential for the accuracy and precision of the determination, we use a fully automated fusion technique, SGE 21, Schoeps. This minimizes potential errors usually associated with manual preparation methods. The glass disks are used for both major and trace element determination are prepared by using mixtures of lithium tetraborate and lithium metaborate, Spectromelt A 12, Merck. For the dilution 4200 mg of this flux and 700 mg of the sample are weighed in platinum-gold crucibles and fused for 15 min at 1100oC. The melt is poured into pre-heated, polished 32 mm-diameter moulds.

All elements are analysed using the SSTmAX-4-kW rhodium target X-ray tube for sample excitation. X-ray spectra are generally less complex than other optical spectra and line interferences can often be avoided through the use of a variety of different crystals. Our XRF spectrometer, AXIOS-Advanced, PANalytical, is equipped with seven mostly laterally curved monochromators PX-10, LiF 220, InSb111, Ge111, PE002, PX-8 and PX-1. Flow-, scintillation-, and sealed Xe-counters are used and pulse-height selection is applied to reduce interferences from higher order spectral lines and background noise. Interference corrections for line overlap are calculated for elements like for example Zr, Nb, Y, Th. The Axios spectrometer is equipped with the SuperQ 4 software.

For the calibration of major and trace element determination, about 50 reference materials are used, a wide variety of international geochemical reference samples from the US Geological Survey, the International Working Group " Analytical standards of minerals, ores and rocks", the National Research Council of Canada, the Geological Survey of Japan, the South African Bureau of Standards, the National Institute of Standards & Technology, etc. These reference materials are used to calibrate our instrument, to test out newly developed analytical programms and to control every-day work.
For external control of our results we regularly participate in the international proficiency testing programm of P. J. Potts, Open University, Milton Keynes.
For the analyses of major elements the analytical precision is better than 1-2%. For trace element determinations the standard deviations of consecutive analyses are in the range of 2 to 5 % relative at the level of 20 to 30 ppm. Detection limits vary from 3 to 0.5ppm for the majority of the measured elements.