It is crucially important to get precise and accurate analytical results for the manufacturer to reduce the level of uncertainty associated with the concentrations of its products, and thus avoid huge losses in revenue. However, even without knowing the whole analytical chain, including the weighing step in sample preparation before fusion, companies often make major investments in state-of-the-art X-ray fluorescence (XRF) equipment. Precision and accuracy of results.
It is essential to know the exact weights of the sample and the flux (sample-to-flux ratio) for in-sample preparation by fusion for XRF analysis. As a consequence, the quality of analytical results given by the spectrometer will be affected by the weighing method, the tolerance accepted, as well as the analytical method to obtain this ratio.
The sample and the flux before fusion can be weighed in several different ways:
- Manual weighing (most commonly used technique)
- Using an automatic instrument
- Directly weighing the sample and the flux in the platinum (Pt) crucible
- Using another container to weigh the sample or the flux before transferring it into the Pt crucible
- Using pre-weighed flux vials
- Correcting the weight on the XRF instrument (exact weight needs to be known)
The precision of the sample-to-flux ratio is affected by all of these weighing methods, which, as a consequence, will impact the final analytical results. Table 1 describes each weighing method tested in this study, along with the corresponding abbreviation used in the text. This study compared the effects of the different weighing methods on the precision (RSD) of the obtained XRF results.
Instrumentation
The weighing step was performed using automatic dispensing balances (Claisse® LeDoser and LeDoser-12) with high precision before fusion (where applicable). The sample preparation before fusion used both ratio and catchweight modes (see Table 1 for details). 40 mm lithium borate glass disks were created using a Claisse LeNeo® fusion instrument. Possible sources of error induced by the mold surface in XRF analysis were eliminated by using the same mold throughout the whole sample preparation process.
The glass disks were analyzed using a Malvern Panalytical 4 kW WDXRF spectrometer with a 37 mm collimator mask.
This information has been sourced, reviewed and adapted from materials provided by Malvern Panalytical.
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