The coordination environment of copper in hair can be altered by treatment products.

OBJECTIVE: To determine whether the coordination environment of copper in hair is affected by the shampoo used. METHODS: Electron paramagnetic resonance (EPR) spectroscopy to discriminate between mixed oxygen/nitrogen and mixed oxygen/sulphur coordination of copper after treatment with two different shampoos. RESULTS: Copper with mixed oxygen/nitrogen coordination could be converted to mixed oxygen/sulphur coordination by treating with the appropriate shampoo, but this was not reversible with the products tested, although copper was removed from hair at very high pH values. CONCLUSION: Commercial hair treatment products can have a profound effect on the copper coordination environment in hair, and this must be taken into account in any attempt to use hair as a health marker.

Determination of the coordination environment of Cu(II) in human hair and its possible relevance to health and hair care treatments.

OBJECTIVE: This paper addresses the question of the coordination environment of copper (II) in hair. METHODS: The research is based on electron paramagnetic resonance (EPR), a spectroscopic technique that detects specifically paramagnetic molecules. Samples were investigated from various male and female subjects of different ages and races. RESULTS: The Cu(II) EPR signals seemed to be a combination of two components in widely differing relative proportions, although both have the relationship g(// )> g(⊥) > 2.0 expected for the unpaired electron in a d(x2-y2) orbital and are thus consistent with square planar or tetragonal symmetry for the Cu(II) ion. With a very few samples, the EPR spectra consisted of a single component, and high quality spectra from these samples are presented for use as standard reference results. In one type of complex, (14) N superhyperfine structure (shfs) was resolved and the spectrum corresponds to Cu coordination to mixed O- and N-containing functional groups, although the number of N atoms cannot be determined with certainty. No (14) N shfs was seen in the spectrum from the other type of complex, and its narrow linewidth excluded the possibility of any. Furthermore, the spectral parameters are inconsistent with coordination of the Cu to four O atoms, but consistent with some S coordinated to the Cu. Large variations between the relative proportions of the two Cu(II) forms were observed with a single healthy subject over a 5-year period, thus suggesting that they are determined by 'environmental' factors, possibly hair treatment processes, rather than being markers for the health of the subject. CONCLUSIONS: EPR spectroscopy is a convenient non-destructive method for determining the Cu coordination environment in hair, and could be used to monitor its response to various types of hair treatment.