66 JOURNAL OF COSMETIC SCIENCE Surface analysis of mammal fibers by electron spectroscopy dates back to at least 1972, where Millard studied oxidative surface treatments of wool (3 ). In this early application of XPS, Millard demonstrated the ability to resolve multiple chemical states of sulfur on the surface of the hair fiber. In this technique, electrons ejected by x-ray photon exci­ tation are collected and energy analyzed to provide quantitative elemental and chemical state data. The kinetic energy of the detected photoelectrons reflects the core electron binding energy, (binding energy = x-ray energy - measured electron kinetic energy), which is specific for the emitting element and it's chemical state. Since the kinetic energy of the photoelectrons is limited to the x-ray energy (typically either characteristic Mg ka = 1254.6 eV or Al ka = 1486.7 eV) the transport length through the sample prior to suffering an inelastic collision (inelastic mean free path) is short, 1-3 nm. As a consequence, the electrons finding their way out of the sample and to the detector with energies characteristic of the emitting atom, emerge from no greater than -10 nm into the sample. Overlayers on a sample surface therefore readily attenuate the substrate signal. The XPS technique is capable of observing every element with the exception of H and He. In the Results and Discussion sections of this paper molecular formula will be expressed in terms of C, 0, N, and S. Compositions will be expressed on a 100% basis considering only C, 0, N, and S. In this paper we wish to discuss the chemical modification of the hair fiber surface by the action of hydrogen peroxide based bleaching solutions and the formation of over­ layers as a result of treatment with conditioning formulations. Discussion of the inter­ action between quaternary ammonium based surfactants and the hair surface studied by XPS has been published by the author recently (4). EXPERIMENT AL TREATMENT PROCEDURE European Brown Hair samples for this investigation were obtained from International Hair Importers & Products, Inc., Valhalla, NY. The hair was dipped into a 10 wt% sodium ether sulfate solution and washed by rubbing between the fingers for 1 minute. After washing the hair was thoroughly rinsed with warm distilled water. A portion of the washed hair tress was cut free and set aside to dry for the blank, the other portion would be further treated. The bleaching treatment employed three differing solutions. 1. A 3% hydrogen peroxide solution 2. A 3% hydrogen peroxide solution plus a sodium bisulfile activator at pH = 9. 3. A 3% hydrogen peroxide solution, sodium bisulfite activator, and 0.25% sodium lauryl sulfate, at pH = 9 The three treatments were applied to hair samples for either 30 or 45 minutes, rinsed, and then dried. CONDITIONING TREATMENT FORMULATION The test conditioning formulation prepared for this study is given in Table I. The conditioner was exposed to hair swatches which were previously bleached for 45 minutes

Ingredient Citric acid Stearamidopropyl dimethylamine Cetyl alcohol Stearyl alcohol Glyceryl stearate Stearth-20 Dimethicone HAIR SURFACE CHEMISTRY Table I Test Conditioning Formulation Diester quaternary amine (Armocare VGH-70) Water 67 Active weight (%) 0.2 0.8 1.9 0.8 0.7 0.3 0.9 2.75 Balance with a 3% hydrogen peroxide solution, sodium bisulfite activator, and 0.25% sodium lauryl sulfate, at pH = 9. A 10% conditioning dispersion was prepared as noted above and the hair swatches were exposed for 60 seconds and then rinse for 30 second at 39°C. XPS XPS spectra were collected at room temperature with a Physical Electronics 5600ci electron spectrometer. Excitation of the sample was accomplished with a monochromatic Al k x x-ray source (hv = 1486.7 eV, 250 w) producing an approximately 7 x 3 mm illuminated area on the sample. Photoelectrons from a 0.8 x 0.8 mm area were energy analyzed with a 279 mm mean diameter hemispherical electron energy analyzer. The angle above the surface plane to the electron collection lens axis was 4 5 ° . Surface charge neutralization was performed with an electron flood gun source, nominally operated at 18 ma emission and 0. 5 V acceleration potential. Exact flood gun conditions were optimized for each sample to obtain minimum peak width with the hydrocarbon C(ls) binding energy around 284.4-284.0 eV. Duplicate analyses were run from the hair fiber samples for collection of elemental survey and high resolution chemical state data. Differing areas of the mounted hair fibers were selected using the internal optical microscope to obtain results from separate areas on the fibers. Low resolution, "survey scan" and high resolution chemical state spectra were collected in fixed analyzer transmission mode at pass energies of 187 .85 eV and 23.50 eV re­ spectively. Spectrometer resolution, measured as full width at half maximum of the 3d5/2 photo electron peak from Ag foil were, 2.4 eV (187.85 eV pass energy) and 0.8 eV (23.5 3 V pass energy). Binding energy scale calibration was performed as described in the E-42 ASTM-902 document. The procedure employs the peak separation of the Cu(2p3/2) and Cu (3p3/2) photoelectron peaks to first establish scale linearity. The Cu photopeaks and the Cu (KLL) Auger peak positions are then used to calibrate the absolute energy scale. Binding energy assignments for the charge compensated (shifted) sample spectra were based on an assignment of the hydrocarbon (-CH2-) C(ls) component in the high resolution C(ls) spectrum being at 284.8 eV. Samples for every analysis were taken from as near the mid-point along the length of the hair tress as could be reproducibly achieved. Hair fibers were mounted between two,