72 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table VII Oxidation Levels of Hair After 12 Weeks of Outdoor Weathering* 1042 cm- • Treatment 1076 cm- • Unexposed (heat and moisture only) or Exposed (heat + moisture + UV) Waved unexposed or waved exposed Bleached unexposed or bleached exposed Sh-O. 12 o. 17-0.57 1.26-1.88 * Each group includes blond and brown hair. the splitting of the same number of disulfide groups. This was not the case, indicating that more disulfide bonds were attacked by bisulfite than by the bleaching process. Hair diameter is a parameter that affects the results. In a diamond cell, the entire hair fiber is viewed in transmission. Oxidative attack is likely to be concentrated in the cuticle and outer cortical cells. This is because of the impervious nature of the cuticle scales and because cystine is more concentrated in the cuticle than in the cortex, with very little found in the medulla (8, 16). Infrared analysis of hair in transmission will determine the oxidation of sulfur in the entire hair. A surface analysis method (such as multiple internal reflectance) would probably show higher percentages of oxidation and may even yield more reproducible results. 30- 2o u g_ o Bleach Strength Figure 5. Plot of percentage of sulfur atoms oxidized as a function of bleaching strength.

FOURIER TRANSFORM INFRARED SPECTROSCOPY OF HAIR 73 CONCLUSIONS The diamond cell-FTIR technique offers a rapid method to quantify oxidative hair damage incurred by various proceses such as weathering, waving, bleaching, or com- binations thereof. Oxidative damage varies considerably along a single hair fiber, with the greatest damage occurring near the tip. The magnitude of this variation is comparable to that found in replicate determinations within a tress and is likely to be the prime source of the latter variation. Hair diameter must also be considered a source of variation when transmission IR is used. While we feel the accuracy of any single absorbance ratio is high, the small sample size used in each measurement limits the precision of repeat determinations. We have shown, however, that triplicate determinations yield reproducible average oxidation values. Obtaining sulfonate absorbance intensities after spectral subtraction improves the precision of the method. Sulfonate bonds formed from oxidative disulfide bond fission are readily distinguished from Bunte salt thiosulfonate bonds formed by bisulfite treatment. Using spectral subtraction, complete spectra of oxidized species can be elucidated, which should permit qualitative differentiation of oxidation mechanisms. ACKNOWLEDGEMENTS The authors acknowledge the efforts of E. Cottington and R. Grubb for performing many of the analyses in these studies and thank I. T. Smith for many helpful discus- sions. REFERENCES (1) G. J. Weston, The infrared spectrum of peracetic acid-treated wool, Biochim. Biophys. Acta,, 47, 462-464 (1955). (2) A. Strasheim and K. Buijs, An infrared study of the oxidation of the disulfide bond in wool, Biochim. Biophys. Acta., 47, 538-541 (1961). (3) C. Robbins, Infrared analysis of oxidized keratins, Text. Res. J., 37, 811-813, (1967). (4) R. C. Shah and R. S. Gandhi, Infrared analysis of oxidized keratins, Text. Res. J., 38, 874-875 (1968). (5) H. Alter and M. Bit-Alkhas, Infrared analysis of oxidized keratins, Text. Res. J., 39, 479-481 (1969). (6) L. J. Bellamy, The Infrared Spectra of Complex Molecules, 3rd ed. (Wiley, New York, 1975), pp 407- 408. (7) N. B. Colthup, L. H. Daly, and S. E. Wiberley, Introduction to Infrared and Raman Spectroscopy, (Academic Press, New York, 1964), p 310. (8) C. R. Robbins, Chemical and Physical Behavior of Human Hair, (Van Nostrand Reinhold, New York, 1979), pp 29, 70. (9) L. J. Wolfram, "The Reactivity of Human Hair. A Review," in Hair Research Status and Future Aspects, C. E. Orfanos, W. Montagna, and G. Stuttgen, Eds. (Springer-Verlag, Berlin, 1981), pp 479-500. 10) M. Bit-Alkhas, Unpublished internal Gillette Co. reports. 11) C. E. Weir, E. R. Lippincott, A. Van Valkenburg, and E. N. Bunting, Infrared studies in the 1 •m to 15 •m region to 30,000 atmospheres, J. Res. Nat. Bur. Standards, A63, 55 (1959). 12) C. V. Poucherr, The Aldrich Library of Infrared Spectra, 3rd ed. (The Aldrich Chem. Co., Milwaukee, 1981), p 536.