It is a challenging task to analyze some samples in the metal industry. Using an inappropriate sample preparation technique can cause inconsistent analytical results and even make the samples impossible to analyze. For instance, problems can occur with concentrates containing partly reduced materials when lithium borate fusion is used. During the sample preparation process, if this kind of sample is not properly oxidized, it can chemically alloy and attack the platinumware. Moreover, volatile elements can be lost if the fusion process is not optimal. These elements are important for the sample type and its characterization to be accurately determined.
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Image Credits: shutterstock.com/Phonlamai Photo
Apparatus and Instrumental Conditions
Here, 40 mm lithium borate glass disks were created using an automatic Claisse® TheOx® Advanced fusion instrument. Uniform heating can be achieved due to the resistance-based electric system, preset fusion programs, and outstanding insulation properties of the instrument, thus yielding repeatable and reproducible fusion conditions and a perfect retention of volatile elements.
Glass disks were analyzed using a Panalytical 4 kW MagiX PRO sequential WDXRF and a 37 mm collimator mask.
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Global Sample Preparation Method
The concentrate samples were prepared in a LiT/LiBr 99.5/0.5 flux, pure grade (99.98+%), using a 1:20 dilution ratio. This flux was weighed using the same Pt/Au crucible where the sample was weighed. The sample was fused using a fully automatic TheOx Advanced instrument.
A single fusion method was designed for all the different sample matrices. An additive is required for this fusion method to ensure the retention and complete oxidation of sulfur. The time taken for the whole cold-to-cold fusion process was 24 minutes, including the oxidation step.
After the oxidation and dilution of the sample in the melted borate flux, it was automatically poured into a 40 mm diameter Pt/Au shallow mold.
Challenges
- The platinumware employed in the sample preparation process can be attacked and damaged by a partially oxidized sample, thus increasing costs
- Achieve a high reproducibility and inter-position repeatability for stable sample preparation
Benefits
- Simple and rapid sample preparation for tricky samples
- Prevent chemical attacks on platinumware
- Prevent the loss of volatile elements in fusion
- Precise results
Results
Six replicates were prepared. Although many elements can be analyzed using this method, Table 1 lists the results collected for five elements of interest. The chart displays the calibration range (in %) and the relative standard deviation (RSD) obtained on the replicates.
Table 1. Composition Ranges and Precision (in %)
| Compound |
Range (%) |
RSD (%) |
| Ag2O |
0-1.5 |
1.0 |
| ZnO |
15-25 |
0.5 |
| PbO |
15-25 |
0.6 |
| CuO |
15-25 |
0.6 |
| SO3 |
25-45 |
1.2 |
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Conclusion
Table able results show that sample preparation by borate fusion and subsequent XRF analysis provide an effective method to analyze concentrates for majors, volatile elements, and silver.
The method demonstrated good precision of sensitive elements such as silver, and an outstanding retention of volatile elements such as sulfur, confirming the quality of the approach. This shows that reproducible and efficient results can be achieved using the TheOx Advanced fusion instrument, despite the presence of volatile and partially oxidized elements in the samples.
Claisse® TheOx® Advanced
This information has been sourced, reviewed and adapted from materials provided by Claisse.
For more information on this source, please visit Claisse.