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Sample preparation for X-ray fluorescence analysis V. / Fusion bead method—part 2: practical applications

Winter 2016 Vol.32 No.1
17-21
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Mitsuru Watanabe

The general preparation method of fusion bead, equipment, reagents and other important considerations were described in the previous article “Sample preparation for X-ray fluorescence analysis IV Fusion bead method—part 1 basic principles.” In this article, the preparation methods of various applications such as ferroalloy, sulfide and carbide are described.

Conventionally, these samples had been prepared as fusion beads after they were oxidized completely by mixing with a strong acid followed by drying. However, raising the temperature of the strong acids such as nitric acid degrades the working environment and the surrounding equipment corrodes due to its oxidizing power. Therefore, it has been necessary to work in a well-ventilated environment.

In the preparation method described here, oxidation reaction progresses slowly in the platinum crucible by oxidizing agent or oxidation catalyst without the use of strong acids. Thus it is possible to prepare fusion beads in a short time in a conventional environment. It should be noted that the described procedure assumes that grain size of the powder samples and the drying temperature of the samples and reagents are those for common fusion bead preparation methods.

If the grain size of the sample is coarse and the fusion bead is prepared without spreading the flux on the bottom of the platinum crucible, the sample will be oxidized insufficiently and form an alloy with the platinum in the crucible and cause irreversible damage. In this case, recasting of crucible may be required. For this reason, it is necessary to perform sample preparation carefully. Other additional analytical considerations regarding measurement of fusion bead are described at the end.