Elemental analysis of mined ore, its concentrates and reﬁned products is an important part of any mining and metal reﬁning operation. X-ray Fluorescence (XRF) spectrometry has proven to be a very reliable and cost-effective elemental analysis technique. As shown by this scientific poster high performance wavelength-dispersive X-ray fluorescence (WD-XRF) has multiple applications in mining laboratories. But what about energy-dispersive X-ray fluorescence (EDXRF)? Is this technique suitable to handle a common application such as the determination of zinc (Zn), lead (Pb), barium (Ba), iron (Fe) and silicon (Si) in a variety of sulﬁde ores?
We took this challenge to an EDXRF spectrometer.
The EDXRF spectrometer we used for the testing combines a low-power X-ray tube and a single highly sensitive Si(Li) detector to generate and measure the emission lines of all elements from Sodium (Na, Z=11) to Uranium (U, Z=92). While EDXRF has increasingly limited sensitivity to lighter elements and is rarely used to measure Sodium (Na) or Magnesium (Mg) at concentrations below 1 %, medium to heavy element sensitivity can easily compete with more expensive WDXRF spectrometers, in some cases even outperforming it.
In EDXRF, primary beam filters allow for targeted excitation to ﬂuoresce only the elements of interest assuring the necessary sensitivity and precision. An instrument with more ﬂexibility and control over the excitation efficiency and background suppression typically shows better performance.
In this case, three spectra were collected off each ore sample, for a total counting time of 3 minutes in a low vacuum atmosphere. The analytical settings are shown below. Each spectrum is acquired with a different filter/excitation voltage combination, optimizing for different analytes.
The results reported below were obtained using multivariate regression analysis based on 14 secondary standards with nominal values obtained by Inductively Coupled Plasma spectroscopy (ICP). This table shows the Standard Error of Estimate (SEE) for the analytes of interest. The SEE is the average difference between the nominal and calculated concentrations of a given analyte and is a measure of the accuracy of the calculated concentrations.
Repeatability tests were also performed to show the precision achieved for the 3-minute total counting time. Below are the results for one of the analyzed samples showing the repeatability values (1-Sigma).
The EDXRF spectrometer successfully analyzed a variety of elements in mining ore. All it takes is a simple three-minute analysis under vacuum to achieve a precision of less than 1 % relative standard deviation (RSD) for all major components.
Needless to say an EDXRF spectrometer can accurately measure Zn, Pb, Ba, Fe and Si in a variety of sulﬁde ores, and avoids the difficulty, expense and delays associated with traditional wet chemical analysis. You can read the more detailed application note here.