Tech Team · Kintek Solution

XRF (X-ray Fluorescence) analysis requires careful sample preparation to ensure accurate and reliable results. The size and preparation method of the sample play a critical role in the quality of the analysis. Solid samples are typically prepared as pressed pellets or fused beads, with particle sizes ideally less than 50µm (though up to 75µm is acceptable). Pressed pellets are created by grinding the sample to a fine powder and compressing it under high pressure, while fused beads involve mixing the sample with a flux and heating it to high temperatures. The choice of method depends on the sample type, binding properties, and the need to minimize matrix effects or trace element dilution. Proper preparation ensures homogeneity and reduces measurement deviations caused by particle size or composition differences.

Key Points Explained:

1. Sample Preparation Methods:

   • Pressed Pellets: This is the most common method for XRF sample preparation. The sample is ground to a fine powder (ideally <50µm, but up to 75µm is acceptable) and compressed under high pressure using a die set. If the sample does not bind well, a wax binder can be added to improve cohesion.
   • Fused Beads: This method involves mixing the sample with a flux (e.g., lithium tetraborate) and heating it to high temperatures to create a homogeneous glass bead. While this method ensures excellent homogeneity, it may dilute trace elements, making it less suitable for trace analysis.

2. Particle Size Requirements:

   • For accurate XRF analysis, the sample should be ground to a particle size of less than 50µm. Smaller particle sizes ensure better binding under pressure and reduce the risk of measurement errors caused by inhomogeneity. Larger particles (up to 75µm) are acceptable but may compromise the accuracy of the results.

3. Pressing Load Requirements:

   • The pressing load required for pellet preparation varies depending on the sample type:
     • Food samples: 2-4 tons.
     • Pharmaceutical products: Up to 20 tons.
     • Mineral ores: Up to 40 tons.
   • The pressing load ensures the sample binds effectively, creating a dense and uniform pellet for analysis.

4. Importance of Homogeneity:

   • Accurate quantitative analysis requires that the sample composition be as uniform as possible. Differences in particle size or composition can lead to matrix effects or interference from coexisting elements, causing deviations in the measurement results.

5. Equipment and Tools:

   • High-quality equipment is essential for effective sample preparation. This includes:
     • Platinum labware: Used for fusion methods to withstand high temperatures.
     • High-performance fusion furnaces: Ensure consistent heating for fused bead preparation.
     • Chemistry-specific molds: Tailored to the sample type for optimal pellet formation.

6. Advantages of Pressed Pellets:

   • Pressed pellets are a popular choice due to their:
     • High-quality results: Ensures accurate and reproducible measurements.
     • Speed: Relatively quick preparation compared to fused beads.
     • Cost-effectiveness: Lower cost compared to fusion methods, making it accessible for routine analysis.

By following these guidelines, users can ensure that their samples are prepared to the highest standards, minimizing errors and achieving reliable XRF analysis results.

Summary Table:

Aspect	Details
Ideal Particle Size	<50µm (up to 75µm acceptable)
Preparation Methods	Pressed pellets or fused beads
Pressing Load	Food: 2-4 tons, Pharma: up to 20 tons, Mineral ores: up to 40 tons
Key Equipment	Platinum labware, fusion furnaces, chemistry-specific molds
Advantages of Pellets	High-quality results, fast preparation, cost-effective for routine analysis

Ensure accurate XRF analysis with proper sample preparation—contact our experts today for guidance!