Recycling-oriented methodology to sample and characterize the metal composition of waste Printed Circuit Boards

•This study presents sampling procedure to obtain spent PCBs reproducible samples.•A methodology with aqua regia digestion was used to determine metal contents.•This method was fully suitable for Cu, Fe, Al, Zn, Pb and Co.•It was slightly less suitable for Ni, Ag, Ga and Pd, but can still be used.•For Au, Sn and Ta, further work should be performed to improve the methodology.