Electronic waste streams are an important source of large quantities of critical raw materials that underpin our society. As such, the European Commission has set new targets for recycling electronic waste in order to achieve a circular economy and reduce dependence on imports from other countries [1]. One of the current major issues is the difficulty faced in analysing the wastes and quantifying the metal contents – a key step in determining the correct recycling pathways and in estimating the economic value of the waste stream.

As part of the MetroCycleEU project [2], which aimed to quantify Technology-Critical Elements (TCE) in urban waste, an inter-laboratory comparison was conducted between 10 research institutions across Europe on printed circuit board (PCB), light emitting diode (LED), and lithium (Li)-ion battery materials. Each institute provided multiple analyses of the materials, covering a range of x-ray fluorescence (XRF) and inductively coupled plasma (ICP) tandem mass spectrometry (MS/MS) and ICP-optical emission spectrometry (OES). Additionally, instrumental neutron activation analysis (INAA) was carried out as the “gold standard” analytical technique.

The results of the study clearly highlighted key aspects that affect determinations of critical elements in electronic waste streams – In particular the limits of detection, interferences, and sample preparation. XRF generally performed well for major components (mass fraction > 0.1%), however suffered greatly for minor components due to the detection limits and spectral interferences from the major components. For ICP-based methods, the sample preparation was identified as the key factor for sources of bias. While results for many determined elements, such as Au, Pd, Cu, Ni, Co, Mn and Fe, were found to agree with the INAA reference result for many different acid digestion procedures, other element, such as Ti and Al, indicated severe biases depending on the acid mixtures used. As such, aqueous digests are required to be tailored towards specific analytes of interest.

References

[1] European Commission COM, 2023, 160 final.

[2] MetroCycleEU (20IND01) www.metrocycle.eu