j. Soc. Cosmet. Chem., 46, 100-116 (March/April 1995) Fingerprinting of cosmetic formulations by dynamic electrokinetic and permeability analysis. II. Hair conditioners J. JACHOWICZ, Clairol Inc., 2 Blachley Road, Stamford CT Received October 26, 1994. Synopsis Dynamic electrokinetic and permeability analysis (DEPA) was employed to investigate complete formula- tions of rinse-off hair conditioners as well as several types of raw materials frequently used as active ingredients in such compositions. Quaternary ammonium surfactants, fatty amines, and silicone emulsions were employed as model systems. Zeta potential and permeability data collected before and after the treatment of hair plugs with 0.5% or 1% solutions of single- or multi-component solutions, respectively, allowed the comparison of their ability to modify hair surface. In general, the conditioners were found to deposit layers of surfactants or polymers with a thickness in the range of 0.6-3.2 •m as calculated from the permeability data obtained for the wet fibers. The systems containing positively charged species were also shown to reverse the surface charge of hair, while those based on neutral, fatty acid-fatty amine complexes or hydrocarbon oil (petrolatum) did not affect significantly the electrostatic surface characteristics. The removability of the conditioner residues was tested by consecutive application of a conditioner and a shampoo solution. The effectiveness of this process was gauged by comparing the thickness of the surface deposits and a value of zeta potential before and after the shampoo application. INTRODUCTION In a previous publication we described the application of dynamic electrokinetic and permeability analysis (DEPA) for testing the interactions of hair with shampoos (1). The technique enabled us to detect and quantify (in terms of streaming potential, zeta potentials, conductivity, and permeability) the adsorption and desorption of various shampoo ingredients on hair. We have now extended this line of research to the analysis of complete formulations of commercial and model hair conditioners. These composi- tions are usually based on surfactants, polymers, or oils possessing high affinity to keratin, and are formulated in such a way that the deposition of active materials occurs within a short period of contact time with the hair surface (2,3). The extent of the surface modification, which is related to the conditioning effect, can be controlled by the choice of the type and concentration of active ingredients, emulsifying agents, pH, etc. The author's present address is International Specialty Products, 1360 Alps Road, Wayne, NJ 07470. 100

DYNAMIC ELECTROKINETIC AND PERMEABILITY ANALYSIS t0 t For example, in the case of saturated single-chain quaternary ammonium surfactants, which are frequently employed in conditioning compositions, the deposited amounts increase with the length of the fatty chain from C•2 to C2o (2,4,5). Formulations based on double- or triple-chain quaternary ammonium surfactants, which are water-insoluble and form lammellar phases, are sensitive to the processing conditions (temperature, agitation) that might affect the size and distribution of the dispersed conditioning agent (5). The performance of the systems based on the emulsified silicone or hydrocarbon oils is influenced by factors such as the extent of oil modification with cationic substituents, the size of the dispersed phase, and the nature of the emulsifying system (6). Other formulation components, such as the thickening agents, emollients, or auxiliary con- ditioning ingredients employed to improve the tactile or rheological characteristics of a formulation, can also affect the deposition of actives and, consequently, the final con- ditioning effect (7,8). An additional, important factor that prompted these investigations is the need for objective testing methods of hair conditioners. Presently the efficacy of these formula- tions is usually analyzed either by subjective salon or consumer use evaluations or by employing laboratory techniques such as combing measurements (9). While consumer tests are time-consuming and expensive, combing evaluations are subject to a relatively large experimental error that makes them insensitive to smaller variations in the for- mulation performance. In this paper we present the dynamic electrokinetic and perme- ability analysis data obtained for selected model compounds frequently used in formu- lating conditioners, as well as for complete, commercial, or prototype products. As previously expressed (t, t0), the set of the electrokinetic and permeability data obtained during an experiment is used to characterize the interactions between the formulation actives and hair. The main purpose of this work was to provide the evidence that DEPA, which measures the fiber characteristics in a dynamic mode as a function of rinsing time with the test solution (5 X t0-5 M KC1), is capable of discriminating between for- mulations based on different active ingredients. EXPERIMENTAL INSTRUMENTATION The instrumentation and the experimental procedures were the same as employed in our previous work (1). MATERIALS Samples of hair. All fiber samples were commercially blended virgin brown hair pur- chased from DeMeo Brothers, New York. The hair was precleaned with a nonionic surfactant, Triton X-tOO, and thoroughly rinsed under deionized water. Hair samples were then soaked in several water baths and extensively rinsed with deionized water to ensure complete removal of residual surfactant. Hair swatches were dried at 37øC. Surfactants and polymers. PEG-15 tallow polyamine (Polyquart H) was in the form of 50% aqueous solution and was obtained from Henkel. Linseed oil amidopropyldi- methylamine (LAPDA, commercial name Foaminolin-80, lot #4136) was provided by