Studies on residual aryl amine content on discharge printed silk fabrics

Degummed and bleached tabby silk fabric was dyed with easily dischargeable azo dyes and discharge printed with zinc sulphoxylate‐formaldehyde. The aryl amines released during the discharge printing were quantitatively recovered and identified by using gas chromatography mass spectrometry. Quantitative analysis by HPLC of the regenerated aryl amines shows that the initial soaking and one rinsing removes more than 43% of the amines in the case of benzidine‐based azo dyes. The quantity of the residual amine (benzidine) retained by the benzidine‐based dyes even after fourth rinsing was in the range of 300–780 mg/kg. This compared with acid dye (CI Acid Red 114) based on o‐toluidine, released 70% of the regenerated amine in the first rinsing itself and 84% after the fourth rinsing.