Development and application of reference and routine analytical methods providing SI-traceable results for the determination of technology-critical elements in PCB from WEEE†

The recovery and reprocessing of technology-critical elements (TCE) present in printed circuit boards (PCB) from electrical and electronic waste is essential both for recycling valuable materials subject to supply risk and for reducing the environmental impact. Although the quantitative knowledge of TCE amounts in end-of-life PCB plays a key role, there are neither matrix certified reference materials nor harmonized analytical methods available to establish the traceability of the results to the International System of Units. To fill these gaps, we developed and applied five reference analytical methods based on ICP-MS standard addition calibrations and INAA k₀- and relative calibrations suitable to certify reference materials. In addition, we developed and tested six analytical methods based on more commonly used ICP-MS external standard calibrations to provide industry with routine analysis methods. Twenty TCE (Ag, Au, Co, Cu, Dy, Ga, Gd, Ge, In, La, Li, Nd, Ni, Pd, Pr, Pt, Rh, Sm, Ta and Ti) were selected as target analytes and a batch of powdered PCB was used as measurement material. An overall mutual agreement was observed among data collected by reference methods at a few percent relative uncertainty levels. Moreover, all but one of the methods developed for routine analysis demonstrated their suitability in industrial applications by producing data within ± 20% of the values established with reference methods.