The sorption of copper (II), manganese (II), zinc (II) and arsenic (III) onto human hair, and their desorption.

Human hair has been studied in relation to sorption from aqueous solutions of Cu2+, Mn2+, Zn2+ and AsO3-(3). At an equilibrium concentration of 0.3 micrograms ml-1 the sorptions are relatively low for Mn (1.1 micrograms g-1) and As (0.1 microgram g-1), and higher for Zn (10 micrograms g-1) and Cu (35 micrograms g-1). But only in the case of copper is the sorption significant relative to the indigenous levels of the elements in the hair. The greater sorption of Cu2+ may be correlated with better binding to the hair fibre, probably both electrostatically and to the sulphur in the keratin. There appears to be at least three modes of attachment, or three mechanisms of attachment of Cu2+ to the hair. An inter-element effect was observed, where Cu2+ severely inhibits the sorption of Zn2+ and Mn2+. Also the total sorption of Cu2+ is reduced on zinc or manganese-treated hair. Some comments are made regarding the results and the problems of exogenous contamination of human hair.