J. Cosmet. Sci., 60, 337–345 (May/June 2009) 337 Copper and calcium uptake in colored hair K. E. SMART, M. KILBURN, M. SCHROEDER, B. G. H. MARTIN, C. HAWES, J. M. MARSH, and C. R. M. GROVENOR, Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK (K.E.S, M.S, C.R.M.G.), School of Life Sciences, Oxford Brookes University, Gipsy Lane, Oxford, OX3 0BP, UK (B.G.H.M., C.H.), Procter & Gamble, Miami Valley Innovation Center, 11810 E. Miami River Road, Cincinnati, OH 45252 (J.M.M.), and Centre for Microscopy, Characterisation & Microanalysis, University of Western Australia, 35 Stirling Highway, Crawley, 6009 WA, Australia (M.K.). Accepted for publication December 29, 2008. Synopsis During hair coloring a number of disulfi de bonds in cystine are oxidized (1) to create cysteic acid, forming binding sites for metal ions such as Ca2+and Cu2+from tap water (2). The increased uptake of these metals can have a detrimental impact on fi ber properties—for example, reducing shine and causing a poor wet and dry feel (3). In addition, the increased uptake of copper can also contribute to further fi ber damage during subse- quent coloring due to its ability to take part in metal-induced radical chemistry (4). It is important to know where in the fi bers these metals are located in order to either effectively remove these metals or control their chemistry. Nanoscale secondary ion mass spectrometry (NanoSIMS) has been used to locate the calcium and copper within hair that has been treated with a colorant and washed multiple times in tap water containing these ions. Untreated hair is used as a baseline standard material. Images with up to 50-nm spatial resolution of the preferential locations of calcium uptake were obtained, showing a high concentration of calcium in the cuticle region of colored hair, specifi cally in the sulfur-rich regions (A-layer and exocuticle). INTRODUCTION Typical permanent hair colorants contain hydrogen peroxide buffered to a pH of 10 with ammonium hydroxide. The role of the oxidant is to bleach the melanin, lightening the under- lying substrate color, and to oxidize the dye precursors to form chromophores. The fi nal color the consumer achieves is a combination of lightening of the natural color and deposi- tion of synthetic color inside the hair. However, the oxidant can also react with the hair proteins and lipids, leading to changes in the fi ber properties that can be experienced by consumers, especially over multiple cycles. These properties include a reduction in shine, reduced manageability, poor wet and dry feel, and increased likelihood of split ends (3). One of the proposed mechanisms of fi ber damage is reaction of the hair proteins and lipids with hydroxyl radical species that are formed from the catalytic reaction between hydrogen Address all correspondence to J. M. Marsh.

JOURNAL OF COSMETIC SCIENCE 338 peroxide and redox metals such as copper (4). The source of the copper is the tap water used during the shampoo and rinsing processes (5). Water hardness ions such as calcium and magnesium are also taken up by hair from the tap water. Although the calcium does not directly take part in the color chemistry, it can affect the shine and combing properties of the hair by forming insoluble calcium salts and soaps on the fi ber surface (6). For both met- als it has been demonstrated that their uptake increases as the hair undergoes multiple treat- ments from an oxidative colorant. It has been hypothesized that this is due to the enhanced number of metal binding sites that are formed in the hair during the oxidation process. The presence of metals in hair has been widely reported in the literature, with earlier work concentrating on measuring the range and levels of metals present in the fi ber (7). This work also demonstrated that there are two main sources of these metals, endogenous and exogenous. The endogenous metals are incorporated in the fi ber at the hair follicle and are thought to act as a pathway for the body to excrete unwanted metals (8). The exogenous metals come from the fi ber’s exposure to the environment and in particular to the water used in its washing (9). Recent research has focused on identifying the specifi c location of metals in the fi ber structure and on identifying which metals are exogenous and which metals are endogenous. Of particular interest has been the presence of metals whose origin may have been due to exposure to pollution. Kempson and Skinner (10) investigated the hair from a worker exposed to lead, and Audinot et al. (11) investigated hair from an individual exposed to arsenic. In both cases the nature of the metal as either exogenous or endogenous was identifi ed. ToF SIMS and x-ray microfl uorescence imaging have been used to map calcium in hair and to identify the source as either exogenous or endogenous (12,13). The technique used here to investigate the location of metals is nanoscale secondary ion mass spectrometry (NanoSIMS). SIMS is a surface analysis technique in which a focused primary ion beam is scanned across the target surface. The bombardment of these primary ions results in the ejection of charged atomic and molecular species from the sample sur- face. The secondary ions are then separated on the basis of their mass-to-charge ratio and correlated to their spatial origin to form a chemical image (14,15). The NanoSIMS is the latest generation of dynamic SIMS facilities and is capable of achieving, at the same time, extremely high spatial resolution ( 50 nm) and mass resolving power (m/∆m = 5,000) due to its coaxial lens confi guration and advanced ion optics. Limited previous work has been done using this kind of analysis on hair samples. The work of Hallegot and Corcuff (16) was the fi rst example of a SIMS study of a hair fi ber, while Collin et al. (17) studied the presence of isotopically labeled taurine in hair. In this study we have concentrated on studying the location of both calcium and copper in hair samples, both untreated and after treatment with an oxidative colorant. EXPERIMENTAL SAMPLE PREPARATION Three samples were used for analysis. The fi rst was untreated Caucasian hair, the second was colored Caucasian hair, and the third was colored Caucasian hair containing high levels of copper. The Caucasian hair containing high levels of copper was used as a control to check the sensitivity of the instrument to detect copper in the hair samples.