Trace element analyses

Accurate net intensities are the basis of good-quality trace element analyses. Furthermore accurate matrix correction is vital, especially in cases where not all major element data are available. Pro-Trace offers specific features for calculating net intensities in trace element analysis and accurate matrix correction when the total matrix is unknown.

Accessed via a periodic table the smart element selector is an easy-to-use feature, which ensures that the user measures the correct combination of elements for a series of element subsets. The channels, instrument parameters and background offsets, are input to the analytical program.

Pro-Trace makes use of shared background positions to reduce measurement times.

Net intensity calculation

Trace element analysis by XRF requires particular attention to be paid to the determination of background intensities beneath analyte peaks, spectral overlap corrections (including cases of mutual interference), and spectral interferences from impurities in the X-ray tube anode. These same problems are of concern in the analysis of major and minor constituents.

But, for instance, it is far less critical for the background intensity estimates to be highly accurate when the peak to background ratio is 50:1 (typical for a major or minor element) compared to values of 3:1 or 2:1 or even less, which is common for trace element determinations.

The aim of Pro-Trace is to obtain the most accurate possible net intensities for analyte peaks, which may be subject to large proportionate corrections for background and spectral overlap. 

Accurate matrix correction with unknown total matrix

If no major element data are available, it is not possible to use either the FP model or the classic model with influence coefficients. The analyst must then revert to the ‘ratio channel’ with a classic model. However, it is not possible to use this approach for analyte wavelengths where there is a major/minor element absorption edge between the tube Compton peak wavelength and the analyte wavelength. The only valid option is to use the Pro-Trace (MAC) matrix model with options to ‘cross’ the major element absorption edge(s). 

Setup samples reduce the need for reference materials

A key feature of Pro-Trace is the use of specially prepared blank specimens and calibration setup samples. These setup samples are calibrated against more than 200 international certified reference materials, providing major cost savings for laboratories that do not have such an extensive library of standards in-house.

At Malvern Panalytical’s Nottingham facility, where the Pro-Trace setup samples are manufactured, the Pro-Trace method is accredited by UKAS to ISO17025. 

Easy routine operation

Once Pro-Trace is set up by the more experienced XRF user, routine operators benefit from the greatly improved accuracy without ever needing to touch Pro-Trace. All sophisticated accuracy enhancements take place under the bonnet.

Special dialogues have been designed for setting up MAC (mass absorption coefficient) calculation, background correction, line overlap correction, tube impurity correction and Feather and Willis background correction calculation. The smart element selector that is accessed via a periodic table is an easy-to-use feature, which ensures that the user measures the correct combination of elements for a series of element subsets. 

The Pro-Trace package is available for the Zetium spectrometer for the analysis of trace elements in materials of geological and environmental significance.