106 JOURNAL OF COSMETIC SCIENCE 100 80 -• •, _ o 70 o 60 - o 50- 40- 3O 0.000 0.005 0.010 0.015 0.020 % SLS 0.025 0.030 ß Douche/SLS O DI Water ß DI Water/SLS ß DI Water (ph=4)/SLS Figure 3. Sodium chloride-based douche/SLS solutions. 88% of the material, but in deionized water, with its pH adjusted to approximately 4 with HCI (darkened triangle, Figure 3), the cleansing dropped to 76%. The ability of SLS to cleanse by surfactant action relies on its ability to form micelies, but in acidic solution, SLS is not ionized to any great extent, and so no micelies are formed. If micelles are not formed, then the surfactant activity of SLS is reduced, resulting in drastically reduced blood cleansing. CETYL PYRIDINIUM CHLORIDE CPCI, as a cationic surfactant, is not recognized as a particularly powerful surfactant

SURFACTANTS AND BLOOD CLEANSING BY SLS SOLUTIONS 107 therefore, the cleansing associated with the CPC1/sodium chloride solutions can be attributed mainly to the sodium chloride (7, Figure 5). In deionized water alone (dark- ened square, Figure 4), a CPC1 solution (0.01%) cleansed 57% of the blood. Although the surface-active cation is able to lyse the cells in a similar fashion as SLS, the surfactant activity of CPC1 is not as adept at cleansing the lysed cell material. As the concentration of CPC1 increases in the sodium chloride solutions (Figure 5), the cleansing decreases. In these situations the CPC1 tyses the cells before they can be carried away from the cloth by the sodium chloride, and once the denatured cellular material is deposited on the cloth, the CPC1 is less effective in cleansing. According to the data, the majority of the cleansing in these solutions is done by the sodium chloride where it lifts the blood cells off the cloth and they are distributed within the solution. The cells begin to lyse as the concentration of CPC1 increases, and the sodium chloride cannot lift the cellular material away from the cloth. "øø t o o o 9O 8O 7O 6O 5O 4O 3O 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 % CpCl ß NaC1 Solution/CPCl ¸ DI Water ß DI Water/CPC1 Figure 4. 0.9% NaC1/CPC1 solutions.