Comparative study of metal ion interactions with wool keratin using chemometrics

Abstract

Uptakes of chromium(III), copper(II), iron(II), nickel(II) and zinc(II) by wool were determined by inductively coupled plasma atomic emission and flame atomic absorption spectrometry. The order of uptakes at 100 °C for these metal ions was found to be Cu^II≫ Zn^II > Cr^III > Fe^II > Ni^II. Further, the metal ion-treated wool samples were submitted to Fourier transform infrared spectrometric analysis, which was facilitated by chemometric methods (principal components analysis, soft independent modelling of class analogies and fuzzy clustering). This revealed the order of structure modification at the carboxyl group as a result of metal ion–wool interactions to be Cr^III > Cu^II≫ Zn^II > Fe^II≈ Ni^II. The difference between the above two rank orders suggests that relatively large uptakes do not necessarily lead to the most significant structurally interactive effects in wool keratin.