Flux & Chemicals by :
When choosing a Lithium Borate Flux for your XRF or ICP application there are a number of factors to be considered:
The melting point of the flux should be sufficiently high so that the sample is fully dissolved but not too high that it causes volatilisation. This is particularly important for volatile compounds such as those containing Na, K and S.
The purity of the flux is important in minimising sample contamination and background intensities. Where trace level accuracy is required (particularly for ICP), the purity of the flux is critical.
The level of moisture retention in the flux can have a significant impact on the weighing accuracy and fusion process. In general, pre-fused fluxes minimise water absorption over extended periods.
The choice of flux depends on the acidity/basicity of the sample and ideally the combination of flux and sample should be as close to neutral as possible.
Different flux manufacturing processes, although chemically identical, have different physical structures. Beaded, granular and powder are some of the more common types. The flux type has a large impact on the hygroscopy, weighing accuracy and melting rates. A pre-fused flux with a controlled particle size and low dust will provide the optimum conditions for fusion.
There are a number of additives that can be added to the flux to improve the overall outcome:
Oxidant: this helps ensure that full oxidation of all compounds takes place either before flux melting or during the fusion process. It is important in reducing chemical attack of platinum labware and attaining a successful fusion bead.
Releasing agent: certain samples can stick to the mould, a releasing agent (non-wetting agent) assists with the process by increasing the surface tension of the molten mix, thereby assisting with release.
XRF Scientific provides flux products that can meet your requirements regardless of which of these factors is most important to you. The graph below provides a recommendation of which flux to use for a range of common samples. For more specialist applications we are always happy to provide support and can often devise a custom solution which is just right for you.
12:22 – Lithium Tetraborate 35.3% / Lithium Metaborate 64.7%
X-ray Flux Type: 12:22
This eutectic flux is “alkaline” and has universal application particularly for alumino-silicates and more acidic oxides. It is generally less prone to cracking and is suitable for most materials such as iron ore, mineral sands, cement, nickel ore and general laboratory analysis.
The melting temperature of this flux is significantly lower than the above fluxes at 825 degrees C and the life of platinum ware and fusion apparatus is therefore prolonged by using this flux. This flux formula was originally developed in Australia and is used exclusively by the iron ore, mineral sands, uranium, nickel and cement industries.
50:50 – Lithium Tetraborate / Lithium Metaborate
X-ray Flux Type: 50:50
This flux is a general purpose flux formulated for use with neutral samples.
66:34 – Lithium Tetraborate 66% / Lithium Metaborate 34%
X-ray Flux Type: 66:34
This eutectic flux is more “alkaline” than LT100 and is more suitable for alumino-silicates and calcareous refractories. The melting temperature is 875 degrees C.
Custom X-ray Flux
Depending on the application, borate fluxes are not always the most suitable solution.
Lanthanum based fluxes
Sodium based fluxes (sodium tetraborate)
Fluoride based fluxes
We can make all X-ray Flux formulations to any customer requirement. Please contact us and let our dedicated staff assist you in meeting your specific X-ray Flux needs. XRF Scientific have developed internal standard fluxes which have been shown to give very high precision results for the analysis of nickel, iron ore and copper. In some instances, the use of internal standards can eliminate the need to carry out high temperature “loss of ignition” with significant cost and time benefits.
Lithium Metaborate 100%
X-ray Flux Type: LM100
Lithium metaborate, LiBO2, often referred to as the ICP flux. Its melting point is 845 °C; it reacts easily with acidic samples and is therefore called a “basic” flux. Suitable for wet chemistry applications.
Lithium Tetraborate 100%
X-ray Flux Type: LT100
This flux is classified as “acidic” and is generally used for higher concentrations of basic oxide samples or for samples containing high proportions of limestone. This flux is not suitable for highly acidic samples.
A major disadvantage of this flux is the relatively high melting temperature (925 degrees C) which causes accelerated wear on platinum apparatus and fusion equipment. In most parts of the world, this flux is being replaced by eutectic pre fused mixtures of lithium tetraborate/lithium metaborate, which give very satisfactory results with significantly lower melting temperatures, thereby prolonging platinum labware life and fusion apparatus.