Tech Team · Kintek Solution

X-ray Fluorescence (XRF) analysis is a versatile technique used to determine the elemental composition of various materials. The type of sample preparation required depends on the sample's physical state (solid, liquid, or powder) and the desired accuracy of the analysis. Solid samples often require polishing to achieve a flat and clean surface, while powders are typically ground and pressed into pellets or fused into beads. Liquid samples are sealed in cups with appropriate films to prevent contamination. Surface finish plays a critical role in the accuracy of XRF analysis, especially for lighter elements, as rough surfaces can scatter and re-absorb longer wavelength elements. Specialized preparation methods, such as using binding agents for geological samples or selecting the right film for liquids, ensure reliable results.

Key Points Explained:

1. Solid Samples:

   • Solid samples for XRF analysis must have a flat and clean surface to ensure accurate measurements.
   • Preparation involves polishing the sample using tools like grinding tools for hard metals or lathes for soft metals.
   • Surface roughness can significantly affect the analysis, especially for lighter elements like carbon or sulfur. Finer finishes yield better results.
   • Contamination must be avoided by using separate tools for different sample types.

2. Powder Samples:

   • Powders are commonly prepared as pressed pellets or fused beads.
     • Pressed Pellets: The sample is ground to a grain size of <75 µm and pressed using a die set. A wax binder may be added if the sample does not bind naturally.
     • Fused Beads: The sample is mixed with a flux and heated to high temperatures to create a homogeneous bead. This method avoids grain size effects but may dilute trace elements.
   • Geological samples, which often contain hard and brittle minerals, are ground into fine powders and mixed with binding agents like cellulose or boric acid to improve pellet formation.

3. Liquid Samples:

   • Liquid samples are prepared by pouring the liquid into a cup and sealing it with a film.
   • The film must provide sufficient support and transmission while preventing contamination.
   • This method is straightforward but requires careful selection of the film material to ensure accurate analysis.

4. Surface Finish and Its Impact:

   • Surface finish is critical for XRF analysis, particularly for lighter elements.
   • Rough surfaces can cause scattering and re-absorption of longer wavelength elements, reducing the accuracy of the analysis.
   • Quantitative analysis often requires finishing the surface with a lathe or grinding paper, with finer finishes yielding better results for lighter elements.

5. Specialized Preparation Methods:

   • For geological samples, binding agents like cellulose or boric acid are used to improve pellet formation and ensure accurate analysis.
   • Fused beads are prepared to avoid the influence of different grain sizes, though this method may dilute trace elements.
   • Consulting specialists or referencing specific articles, such as those on sulfur analysis in fuels by WDXRF, can provide additional guidance for complex applications.

By understanding these preparation methods and their implications, users can ensure accurate and efficient XRF analysis for a wide range of sample types.

Summary Table:

Sample Type	Preparation Method	Key Considerations
Solid	Polishing to achieve a flat, clean surface	Surface roughness affects accuracy, especially for lighter elements
Powder	Pressed pellets or fused beads	Grain size <75 µm, binding agents for geological samples
Liquid	Sealed in cups with appropriate films	Film selection critical for preventing contamination

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