Low-Power Monochromatic Wavelength-Dispersive X-ray Fluorescence-Principle and Applications in Petroleum Products
Pages: 18 Published: Jan 2011
X-ray fluorescence (XRF) using polychromatic X-rays is a powerful elemental analysis tool for petroleum products. XRF with an energy dispersive spectrometer (EDS) provides rapid multielement analysis in oil, lubricants, and raw materials. Energy dispersive XRF (EDXRF) systems can be compact and robust. Several ASTM methods are based on EDXRF techniques, including D4294, D6445, D6481, and D7212. However, the limitations of an EDXRF system include 1) susceptibility to elemental interference due to relatively poor energy resolution, and 2) low limit of detection (LOD) in the range of 5 to 10 ppm for sulfur, chlorine, and phosphorus in low atomic number matrix, which is not adequate for trace-level analysis. Another option, wavelength-dispersive XRF (WDXRF), provides superior energy resolution and lower LOD. A high-power WDXRF system has an LOD of about 0.5 ppm for sulfur, chlorine, and other elements. Several ASTM methods are well established for petroleum applications, including D2622, D6334, and D6376. The disadvantage of a WDXRF system is that it typically requires a high-power X-ray tube in a sophisticated system involving precision alignment and scanning. It is also bulky and not suitable for field testing.
Paper ID: MONO10115M
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