Trace metals can affect hydroxyl radical production and yellowing of photo-irradiated wool

Abstract

Previous studies identified that trace metals within the wool fibre are associated with the production of free radicals and yellowing in photo-irradiated wool, and that protein-bound redox-active transition metals, particularly iron and copper, can catalyse the production of hydroxyl radicals and oxidation of proteins in biological systems. This present study investigated the relationship between trace metal content, hydroxyl radical production, tensile strength and yellowing of photo-irradiated metal-doped wool fabric. Iron increased the production of hydroxyl radicals and phototendering, and both copper and iron increased the rate of photoyellowing. The tensile strength of iron-doped wool fabric decreased whereas the strength of copper-doped wool increased after artificial weathering while wet. Manganese reduced hydroxyl radical production and had little effect on photoyellowing. Antioxidants and chelating agents were added to quench hydroxyl radicals and sequester metal ions. Ascorbic acid, citric acid and ethylenediamine tetraacetic acid increased hydroxyl radical production whereas deferoxamine mesylate (desferal) and diethylenetriamine pentaacetic acid reduced production.

Keywords:

• wool
• trace metals
• wool photostability
• wool photoyellowing

Acknowledgements

The authors thank Cheryl McHugh and her team at CSIRO Process Science and Engineering in Clayton, Melbourne for carrying out ICP-AES analysis on digested wool samples and are grateful to the CRC for Sheep Industry Innovation for providing financial support.