Afterchrome dyeing of wool. Part B — characterisation of chromium‐treated wool by secondary particle mass spectrometry

Secondary particle mass spectrometry has been used for the first time to determine the oxidation state and depth distribution of chromium on and in wool fibres. Wool tops were dyed with 4% o.w.f. CI Mordant Black 11 and aftertreated with 1% o.w.f. potassium dichromate, and wool samples treated in a blank dyebath aftertreated with 6% o.w.f. potassium dichromate were analysed. It could be shown that the absolute concentration of chromium in a surface layer 50 nm thick became enriched with chromium by a factor of two, compared with the bulk fibre. Chromium in the hexavalent oxidation state was found to be mainly present in the outermost part of the fibres, while trivalent chromium was dominant inside the fibres.