Introduction

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

Alloy system       Cu-Zn-Sn-Pb

The Analytical problem

Copper alloys will be often used in a wide range of composition for technical purposes. The most important alloys are brass with a high Zn-content and bronze with a high Sn-content. Other alloying elements can be Pb and Ni, Fe, Sb, Si < 0.5 % too.

From the spectroscopical point of view the overlapping of Cu peaks with those of Zn and Ni has to be solved. But with spectra deconvolution this presents no problem.

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 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. 50 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. Non-homogenities can produce insufficient reproducibility of measurement.

Excitation conditions

Program Parameters

Reference samples

The calibration was divided into two ranges - one for brass with relatively high Zn-content and small Sn-concentration and the other for bronze with relatively high Sn-contents and small Zn-concentrations.

For approximately every 3 - 5 % one reference sample is necessary. For every calibration range analysed here, about 7 reference samples were used.

Analytical results

Limits of detection:

The limits of detection for elements that overlap with Cu (Ni, Zn) are approximately 0.5 %, and for the other elements (Pb, Fe, Sb) 0.2 - 0.3 %.

Brass

Accuracy

Calibration table

Error of fit

For this calibration the following error of the fit was calculated [in Wt %]:

Reproducibility

Repeated measurements (120 s Measuring time) on the same sample gave the following results:

Bronze

Accuracy

Calibration table

Error of fit

For this calibration the following error of the fit was calculated [in Wt %]:

Reproducibility

Repeated measurements (120 s Measuring time) on the same sample gave the following results: