STAINING CATIONICS ON KERATIN 209 CTAC CTAC/C-10 i CTAC/C12 SAC SAC/CI0-2 SAC/C!2 Figure 2. Wool swatches stained with Red-80 dye after treatment with either CTAC or SAC and washing with C10[SDES] or C12[ALS] detergents. Several other anionic detergents were used in this test scheme to try to shed more light on the mechanism of action in this modified staining procedure. The effect of ethoxyla- tion to SLS was examined for washing CTAC from swatches (see Figure 3). For this series of anionic detergents, those swatches washed with the more water-soluble sodium laureth sulfates with 7 and 12 ethoxy units produced staining, while those treated with the less water-soluble species with up to 5 ethoxy units did not stain. Table I Radiotracer Analysis Showing Quantities of Anionic and Cationic Detergents # Bound to Keratin After Treatment With Pure Detergents mg Ionic moiety/gm Dry keratin Treatment Anion Cation Total bound SAC/ALS 4.1' 4.6* 8.7* SAC/SDES 2.1 2.0 4.1 # Keratin contained 6.9 mg SAC/gm dry keratin after treatment with SAC, just prior to washing.. * Significantly different from corresponding value at or beyond the 95% level.
210 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS bOllll'M I)½}1)1.'( 'E'I !1 •! I,FATFS ('TAC ( I•( II•-I.'l' ('1•( I1-1"( ('1'•('/.'4-1.() ('IACIS-I':O C1'•C/7-1"O Ci'M'/12.1,'(} Figure 3. Wool swatches stained with Red-80 dye after treatment with CTAC and washing with laureth sulfate detergents. Thus, the more water-soluble the anionic detergent in this scheme, the more likely for staining to occur. This conclusion is consistent with the results from the initial experi- ment with the alkyl sulfates that is depicted in Figure 1. Here the cationic-treated swatches when washed with the more water-soluble C8 and C 10 alkyl sulfates produced staining, while the swatches washed with the less water-soluble C12 and C14 alkyl sulfates did not stain. Similar results were obtained in an experiment using a series of AOS detergents (see Figure 4). Here, once again, the cationic-treated swatches washed with the more water- soluble detergents provided staining. However, with the AOS detergents, the cutoff point was between the C12 and the C14 detergents, i.e., the swatches washed with the C10 and the C12 detergents stained, while those washed with the less water-soluble C 14 and C 16 detergents did not stain. Cationic conditioners contain lipid materials such as fatty alcohol in addition to the cationic active ingredient. This lipid material adsorbs to the hair along with the cation, and the relative amounts adsorbed depend on the relative concentrations and structures of cationic and lipid (7). The standard Red-80 dye-staining test, involving no washing, often shows a difference in hue of the dye on keratin between swatches treated with cationic vs cationic containing lipid-like cetyl alcohol (see Figure 5). This change in hue of the stain demonstrates that lipids like cetyl alcohol adsorb to the keratin in combina- tion with the cationic. The adsorbed alcohol perturbs the cationic dye interaction pro- duct, shifting the light absorption-reflectance character of the dye on the keratin. Thus the change in hue. Most fully formulated conditioner products or even partially formulated ones containing
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