When conducting XRF (X-ray Fluorescence) analysis, the size of the sample is crucial for accurate results. Typically, a sample surface of either 32 mm or 40 mm diameter is required for round pellets. This ensures adequate coverage and precision in the analysis. The choice between these sizes depends on the specific requirements of the XRF spectrometer and the nature of the sample being analyzed.
What Size Sample is Needed for XRF? (4 Key Considerations)
1. Sample Size and Preparation
For XRF analysis, samples are often prepared in the form of pellets. These pellets are made by compressing powdered samples into a disc shape using a die. The standard sizes for these pellets are 32 mm or 40 mm in diameter. These sizes are chosen to match the requirements of the XRF spectrometers, which are designed to analyze samples of these dimensions.
Different types of dies are available for preparing these pellets. One type has internal pressing pellets suitable for all sample types, while another type is designed for use with aluminum sample cups and features a highly polished plunger face. The choice of die depends on the specific characteristics of the sample and the desired level of sample preparation.
2. Sample Requirements Based on Material
Food samples typically require a lower compression force, around 2-4 tons, due to their softer composition. Pharmaceutical products may require a higher compression force, up to 20 tons, which is ideal for manual XRF presses. Mineral ores may require the highest compression force, up to 40 tons, due to their hardness and density.
3. Alternative Preparation Techniques
Fused beads are an alternative preparation technique used when better homogenization of the sample is required. The sample is ground to a fine particle size (<75 µm) and mixed with a flux (such as lithium tetraborate or a mixture of tetraborate/metaborate) in ratios ranging from 5:1 to 10:1. The mixture is then heated in a platinum crucible to high temperatures (up to 1,600 °C). However, this method has a limitation in that it may not detect trace elements effectively due to sample dilution.
4. Considerations for Sample Preparation
The choice of sample preparation method depends on the quality of results required, the effort willing to be expended (labor, complexity), and the cost (equipment, labor, time to analysis). Different materials may require different preparation methods based on their analysis requirements.
Continue Exploring, Consult Our Experts
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