Characterisation of reduction state of cystine linkages on wool fibre surface under heterogeneous reaction conditions

Abstract

As a natural biomaterial with outstanding properties, keratin fibres hold promising potential in many application fields. The reduction of disulphides in keratin to the corresponding thiols plays a central role e.g. in modification and functionalisation of wool, in hair cosmetics, as well as in advanced applications using keratin as biomaterial. To achieve controlled conditions, the need for a quantitative determination of thiols on the solid wool fibre is evident. This work presents an advanced method of heterogeneous potentiometric back titration method for thiol detection in intact keratin fibres. First, keratin is reductively treated with NaBH4, then the thiol content in keratin is determined using K3[Fe(CN)6] and K2CrO4 as reagents and potentiometric endpoint detection. Thiol concentration in the range between 6.83 and 26.17 (±2.13) μmol/g can be detected with the heterogeneous back titration. Thus, the method is simple in execution and reliable in performance and of significant potential, both as scientific technique to quantify thiols in insoluble keratin material, as well as for process and quality control in industry.