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The XRF facility utilizes a Bruker S8 Tiger sequential wavelength-dispersive x-ray spectrometer for qualitative and quantitative determination of elements. It is equipped with one goniometer, which is capable of holding up to four analyzing crystals. The detection system consists of an argon/methane flow proportional counter and a scintillation counter.
Currrently there are two types of XRF methods being used within the Facility:
Fused Glass Beads Analysis
The determination of the light major elements in geological material using XRF of fused borate glass beads in a very accurate and precise method. While the pressed pellet procedure provides good accuracy for the middle energy elements (K through Fe and Ba and Ce) the light elemts (Na, Mg, Al, Si, and P) are only determined accurately using a homogenous glass sample.
Sample bead preparation is automated using a Leco Fluxer, which simultaneously fabricates six beads. Elements determined by this method are NA, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Ba, Ce, and LOI.
As we require prior analysis by pressed pellet to determine S, As and Fe concentrations, a minimum 15 g of -200 mesh sample powder is required for submission.
Pressed Pellets Analysis
The pressed powder pellet sample preparation technique allow trace elemt determinations, with limits of detection below 1 ppm for selected elements. In addition, comparison of XRF determinations, esp. Rb, Sr, Y, Zr, and Nb, with ICP-MS analysis is a very powerful and necessary quality control mechanism for analytical results. Over the several decades in which XRF has been used in geochemical analysis, there has been a slow but steady evolution of the instrumentation resulting in improved sensitivities and lowered detection limits. Using a combination of improved crystals and longer counting times, the limit of detection for Rb, Y and Nb have been reduced to 0.6 -0.7 ppm.
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