FOURIER TRANSFORM INFRARED SPECTROSCOPY OF HAIR 69 Table III Ratios of the Oxidation Band (1042 cm-l) and Bunte Salt Band (1022 cm-l) After Subtraction Against Peptide Bands for Once-Bisulfite-Waved Hair (Samples C) 1042 1042 1042 1022 1022 1022 Frequency (cm- l) 1650 1235 1235 1650 1235 1235 (Base/ine) (--1900) (--1100) (--900) (--1900) (--1100) (--900) Tress 1 --0.012 --0.076 --0.059 0.021 0.133 0.104 0.005 0.026 0.017 0.012 0.056 0.037 --0.002 --0.012 --0.008 0.014 0.078 0.051 Tress 2 --0.004 --0.016 --0.011 0.022 0.084 0.056 0.015 0.074 0.049 0.023 0.113 0.076 --0.003 --0.019 --0.011 0.013 0.085 0.050 Tress 3 0.008 0.043 0.028 0.023 0.116 0.077 O. 006 O. 027 O. 018 O. 020 O. 086 O. 058 --0.002 --0.011 --0.007 0.009 0.060 0.040 Mean 0.006 0.034 0.023 0.017 0.090 0.061 CV (%)* -- -- -- 30.9 28.7 34.5 Corr. Coeff. ** -- -- -- 0.305 0.642 0.616 Coefficient of variation for 9 determinations. Correlation coefficient of 1022 cm-• band versus peptide band intensities. of replicate tresses was low. The variability between analyses within tresses was about 20% for bleached hair and about 32% for Bunte salt hair. C¾'s between means of replicate tresses was 10-14% for bleached hair and only 4-9% for Bunte salt hair. These results show that three analyses are sufficient for obtaining reproducible oxidation values. Table IV Coefficients of Variation (%) of Absorbance Ratios From Table i Col/•mn 5 Cobiron 7 1042 cm- • 1042 cm- • Bleached Hair 1650 cm- • 1235 cm- t Tress 1 23 17 Tress 2 24 21 Tress 3 24 12 Means of Three Tresses 14 10 From Table III Column 4 Column 5 1022 cm- 1 1022 cm- t Bunte Salt Hair 1650 cm-• 1235 cm-t Tress 1 30 45 Tress 2 28 18 Tress 3 42 32 Means of Three Tresses 9 4

70 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS To explore further the sources of variability of our measurements, two single-bleached hair fibers were analyzed along their length. Each fiber was cut into three equal pieces and each piece was cut into three sections for each analysis. The resulting absorbance ratios are shown in Table V. Considerably more oxidation was found in the tip third than was found in the other two thirds of both fibers. Fiber 1 showed more oxidation in the middle section than in the root portion while these two sections were equivalent in Fiber 2. The results are in agreement with other findings which indicate that the tip of hair is more damaged than the root end (14-17) and hence more susceptible to oxidative attack. DETERMINATION OF BUNTE SALT CONTENT OF HAIR The use of bisulfite waving lotion involves the formation of -S-SO i in the waving stage and oxidation in the neutralization stage. In the spectra of hair tresses subjected to bisulfite waving (samples C), a band was found at 1022 cm-• in addition to the 1042 cm-• (sulfonate) band. This was assigned to the S = O stretching vibration of -S- SO i Bunte salts groups (10,13). Prior to subtraction, the 1022 cm- • bands were not resolved in any of the nine spectra. In three spectra the 1042 cm- • band was resolved and in the remainder only shoulders appeared near 1042 cm-• and 1022 cm-•. After subtraction, the band at 1022 cm-• was strong and well defined, while the 1042 cm- • band was weak and at times appeared as a shoulder under the 1022 cm-• band. The ratios using the 1042 cm-• band in Table III, therefore, are approximations only. Estimates of thiosulfonate (-S-SO•) residues (1022 cm-• band) are much more reliable. EFFECT OF WEATHERING ON HAIR Hair samples exposed to various weathering protocols were also examined. The degree of fiber oxidation was again determined from the ratio of the 1042 cm-• peak height against the hair protein band at 1076 cm- •, using the valley between these bands (near 1050 cm-•) as the baseline for each. Table V Oxidation Absorbance Ratios Measured Along Length of Single Hair Fibers, Once Bleached Before Subtraction After Subtraction 1042 1042 1042 1042 Frequency, cm- • 1076 1650 1235 1235 (Baseline, cm - 1) (• 1050) (-- 1900) (-- 1100) (-- 900) Fiber 1 Root Third 0.676 0.012 0.052 0.073 Mid Third 0.788 0.014 0.063 0.085 Tip Third 1.003 0.015 0.077 0.095 Fiber 2 Root Third 1.517 0.017 0. 102 0. 117 Mid Third 1.500 0.017 0. 104 0.114 Tip Third 2.250 0.019 0. 106 0. 120