Choosing a Flux for XRF Sample Preparation
When performing the fusion method of XRF sample preparation, a flux is a chemical used to dissolve an oxidized sample to produce a fused bead that is free of any mineral structures. Borate fusion is a popular technique and there are a variety of chemicals that can be used as a flux for this method. This blog post will outline some of the factors that should be considered when choosing a flux and the options available.
Flux Considerations
Depending on your application requirements there are various factors that should be considered before selecting a flux.
The purity of the flux can be critical in applications where trace level accuracy is needed. Ensuring high levels of purity is also important to reduce the risk of any sample contamination and background intensities.
When choosing a flux, the ideal combination of sample and flux is neutral. So, consider the acidity or basicity of your sample when selecting the right flux to ensure it is as neutral as possible.
The physical structure of the flux can have many effects on how it performs. Typical structures include beaded, powder, and granular. The type of flux you choose can have a significant impact on the weighing accuracy, melting rates, and hygroscopy of the fusion process. Generally, a pre-fused flux will provide the best conditions for successful fusion.
XRF Scientific Fluxes
XRF Scientific supply a range of flux products that are suitable for all requirements.
Our lithium tetraborate and lithium metaborate products are available in a range of compositions.
For wet chemistry, the lithium metaborate 100% is best suited. It has a melting point of 845oC and it reacts easily with acidic samples. Whereas, the lithium tetraborate 100% flux can be used with copper sulfate, calcium oxide, and magnesium oxide samples. This flux is often used for oxide samples in higher concentrations or samples with high levels of limestone.
The more alkaline fluxes are Lithium Tetraborate 35.3% / Lithium Metaborate 64.7% and Lithium Tetraborate 66% / Lithium Metaborate 34% and are best suited for alumino-silicates.
XRF Scientific also develop and supply custom x-ray fluxes, when a borate flux is not a suitable solution. We can develop lanthanum-based fluxes, sodium-based fluxes, and fluoride-based fluxes, and all of these formulations can be developed to exact specifications.
We also supply pre-weighed fluxes to remove the time and errors associated with weighing flux in a lab.
If you would like any more information about the flux products available from XRF Scientific, please contact us.
