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Sample Preparation - Fusion Bead

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Published Date Written by Sharon Banks

The Key to Analyses - Sample Preparation:
Sample preparation is by far the most important step in any analytical technique. The quality of the sample preparation will affect the ability to yield accurate data from the instrument. X-ray fluorescence is not immune to this crucial step, despite the ability to correct for standard counting errors, instrument variation errors, operational errors, and matrix effects.   Therefore selection of the correct sample preparation technique will depend on the goals of accuracy and precision the analyst needs or wishes to attain.

The key to selecting the appropriate sample preparation technique is maintenance of sample integrity, reproducibility, accuracy, simplicity, cost, and time required for sample preparation.  It is recommended that sample preparation be performed with equipment that is independent of operator technique (for example; the use of a  vibratory splitter that will split independently of the speed at which the operator pours the sample, rather than a riffle splitter which is operator dependent).  Another source of error is sample contamination due to the materials used in the preparation.  For instance in the milling stage of the preparation; the correct selection of milling pot is critical as each type could contaminate the sample with a little of the lining chemicals present in the pot.  Consequently pot selection must be made taking into account the elements to be analysed.
Once the primary sample preparation is complete, the sample is further readied for analysis by the XRF instrument.  Ideally the final sample contains a flat surface, is homogeneous and is infinitely thick with respect to the x-ray.  Two commonly used preparation methods include pressed powder pellets and fusion beads.   Pressed powder pellets entail the compressing of a sample, in the presence of a binder, into a solid tablet.  This method can lead to heterogeneity concerns as issues such as particle size and mineralogical effects need to be considered. For the fusion method heterogeneity is no longer a concern as the sample (which is mixed with a suitable flux) is fused into a glass and cast into a bead, which is homogeneous in nature.
Due to the independence of this method to the mineralogical composition of the sample, UIS Analytical Services has opted to use fusion as our standard method.  This method allows us the flexibility to analyze various sample types by XRF without the need to re-calibrate- thus offering faster turnaround times to our clients.
Should you need any XRF analysis please do not hesitate to contact us.

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