Introduction

This application note gives all recommended data for the described analytical task, including the list of measured values based on certified reference samples.

Alloy system       Pt-Cu

The Analytical problem

The use of Platinum alloys in jewellery has increased constantly. That means there is a need to determine the Pt-concentration in this type of alloy.

From the analytical point of view this task is not easy because the peaks of the components are strongly overlapping. On the other hand the relatively small concentration range eases the evaluation.

The Analytical instrument

Measurements are made with the benchtop spectrometers

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.

Energy dispersive measurement is made with a proportional counter. Despite the limited resolution of this type of detector, highly precise analysis is possible if the qualitative composition of the sample is known. Good statistical measurement guarantees high reproducibility.

Max. Layer Thickness: approx. 10 µm

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.

Further preparation is not necessary as the very small excited area and the use of normalised intensities reduce the geometric influence on the signal.

The irradiated area must be homogeneous. Inhomogenitis can produce insufficient reproducibility of measurement.

Excitation conditions

Program Parameters

Calibration

For the small concentration range three reference samples only were used. During the production of platinum alloys there is the possibility that segregation of the different components can occur due to nonhomogenous cooling from very different melting temperatures. This segregation can produce nonhomogeneous samples. For this reason it is recommended that multiple measurements are made over the surface of the sample and the mean value taken.

Analytical results

Accuracy

Calibration table

Correlation coefficient

For this calibration, there is the following error of the fit: 0.08 Wt.%

That means, that the analytical error for the described alloy system is approximately + 0.10 Wt.%

Reproducibility

Repeated measurements (10 measurements) at the same sample position give the following results

The Standard deviation of analytical results is significantly less than the standard deviation of intensities. This is a result of special evaluation of the spectra.