ISO 17331:2004 specifies chemical methods for the collection of iron and/or nickel from the surface of silicon-wafer working reference materials by the vapour-phase decomposition method or the direct acid droplet decomposition method.

It applies to iron and/or nickel atomic surface densities from 6 times 10 to the power 9 atoms per square centimetre to 5 times 10 to the power 11 atoms per square centimetre.