Introduction |
This application note gives all recommended data for the described analytical task, including the list of measured values based on certified reference samples. |
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Alloy system Ag-Cu |
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The Analytical problem |
Analysis of Silver alloys is an important task in the jewellery industry for the determination of alloy composition and monetary value of alloys. There are no problems from the analytical point of view, because the X-Ray lines used have no overlapping. |
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The Analytical instrument |
Measurements are made with the benchtop spectrometers |
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X-Ray ComPact or |
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X-Ray maXXi |
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A low power tube is used in either instrument in excitation mode. A special collimator reduces the exciting beam down to 0.5 mm diameter. In this way, analysis of irregular or filigree samples will be possible. This is very important for jewellery manufacturers. |
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Energy dispersive measurement is made with a proportional counter. Despite the limited resolution of this type detector, highly precise analysis is possible if the qualitative composition of the sample is known. Good statistical measurement guarantees high reproducibility. |
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Max. Layer Thickness: approx. 100 µm |
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Sample preparation |
The surface of the samples should be thoroughly cleaned free of contaminants. This will enable the irradiated area to be representative of the whole. |
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Further preparation are not necessary as the very small excited area and the use of normalised intensities reduce the geometric influence on the signal. |
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The irradiated area must be homogeneous. Non-homogenities can produce insufficient reproducibility of measurement. |
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Excitation conditions |
| Voltage |
40 kV |
| Power |
approx. 15 W |
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Program Parameters |
| Program |
SRX Vers. 4.104 |
| Evaluation program |
ALLOY.EXE |
| Measuring time for references |
120 s |
| Measuring time for analysis |
120 s |
| Normalisation parameter |
3 |
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Parameter |
Au |
Cu |
| Deconvolution |
On |
On |
| Cmin |
60 |
0 |
| Cmax |
100 |
40 |
| ROI Int min |
364 |
130 |
| ROI Int max |
400 |
150 |
| ROI Decon min |
300 |
90 |
| ROI Decon max |
470 |
180 |
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Reference samples |
For approximately every 5 - 10 % one reference sample is necessary. For the concentration range analysed here, five reference samples were used. |
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Attention: |
Because of the lower cost value of silver, alloys often contain a greater than normal percentage of silver. Hallmarks should not therefore be used as analyticalal references! |
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Analytical results |
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Accuracy |
Calibration table |
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Ag |
Cu |
Given |
Measured |
Given |
Measured |
100.00 |
100.00 |
0.00 |
0.00 |
97.00 |
97.19 |
3.00 |
2.81 |
93.50 |
93.37 |
6.50 |
6.63 |
87.00 |
86.62 |
13.00 |
13.38 |
83.50 |
83.71 |
16.50 |
16.39 |
62.80 |
62.95 |
37.20 |
37.05 |
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Error of fit |
For this calibration the following error of the fit was calculated 0.05 Wt % |
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Reproducibility |
Repeated measurements on the same sample (93 Wt % Ag) gave the following results: |
| SD (Ag-Concentration): |
0.05 Wt % |
| RSD (Ag-Intensity [1*s]): |
0.33 % |
| RSD (Statistic Ag-Intensity): |
0.27 % |
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