J. Soc. Cosmet. Chem., 42, 87-96 (March/April 1991) Colloid titration' A method to quantify the adsorption of cationic polymer by bleached hair JACQUELINE M. HUTTER, MARY T. CLARKE, ERNST K. JUST, J. L. LICHTIN, and ADEL SAKR, Aqualon Company, Wilmington, DE 19850 (.J.M.H., M.T.C., E.K.J.), and University of Cincinnati College of Pharmacy, Cincinnati, OH 45267 (J.M.H., J.L.L., A.S. ) Received September 12, 1990. Synopsis Colloid titration was validated and used to measure the adsorption of cationic polymer by hair. Cationic polymer uptake by bleached hair was measured indirectly by determining concentration differences in treatment solutions following immersion of hair tresses. Uptake of Polyquaternium-10 cationic hydroxyethylcellulose determined by colloid titration correlated with previously published results for a Polyquaternium-10 measured by radiotracing. Adsorption of cationic hydroxyethylcellulose depended on the degree of damage caused by bleaching hair bleached under harsh conditions showed higher levels of cationic polymer adsorption. Sorption of Polyquaternium-10 increased directly with polymer treatment time and cationic solution concentrations. INTRODUCTION Cationic polymers are widely used in hair product formulations for their ability to modify the condition of hair. Positively charged groups on the polymer are attracted to the negatively charged hair surface and adsorption occurs. An adsorbed polymeric film on the hair surface can lead to improved body and combability. These modifications serve to improve the apparent condition of hair (1). The efficacy of a cationic polymer conditioning treatment is directly related to the amount of polymer deposited on the hair surface from treatment solutions. Most methods for detecting the presence of cationic polymer on hair involve analysis of the hair surface for adsorbed agent (1) and include measurements such as wettability (2), electrophoresis (3), streaming potential (5), and a dye test (6). These tests yield only relative information about the surface conditions of hair quantitative assessment of adsorbed species is not possible. Jacqueline M. Hutter's current address is Helene Curtis Industries, 4401 West North Avenue, Building 3E, Chicago, IL 60639. 87

88 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Quantification of adsorbed substances has been demonstrated by application of ra- diotracer techniques (7-8) or by ESCA, i.e., electron spectroscopy for chemical analysis (9). While accurate determination of adsorbed cationic polymer is possible by these latter methods, the techniques are not without difficulty. Radiotracer methodology requires the use of specially synthesized 14C tagged polymers, which may be difficult to obtain. ESCA does not require special types of polymers, but the complexity and limited availability of instrumentation may preclude its routine application. The need for a straightforward method to measure the adsorption of cationic polymer onto hair accurately and routinely has led to an investigation of solution depletion methods of analysis. These methods rely on differences in solution concentration of cationic polymer following immersion of an adsorbing substrate. As such, a concentra- tion difference in cationic polymer before and after immersion is attributed to cationic uptake by the substrate. The colloid titration method has been used to determine charge characteristics of cat- ionic polyelectrolytes (10), as well as the concentration of cationics in solution (11). Quantification of cationic polymer adsorbed onto cellulose fibers (12) and hair (5) via this technique also has limited mention in the literature. The present investigation details procedures needed in using colloid titration for the accurate determination of cationic polymer uptake by hair. EXPERIMENTAL TRESS PREPARATION Medium-dark brown, 8-inch-long, virgin quality European hair (DeMeo Brothers, New York) was mounted on plastic tabs. The mounted hair was washed in a 2.5% ammo- nium lauryl sulfate solution (Stepanol AM, Stepan, Maywood, N J) for 1 minute, rinsed for 1.5 minutes in 40øC running tap water, and air dried thoroughly. Tresses were then bleached (13) in a formulation of 3% hydrogen peroxide (Baker, Phillipsburg, NY). In addition to the normal and recommended bleach time and temperature of 30 minutes at 32øC, much harsher bleaching conditions of 4 hours at 40øC were also used. These samples will be later referred to as "mild" and "harsh" bleach types, respectively. Bleached hair was then soaked overnight in a large volume (8-10 L) of deionized water to thoroughly extract pigment bodies and other substances made soluble by the bleach- ing process. EQUIVALENT WEIGHT DETERMINATION OF CATIONIC POLYMER Solutions containing 0.05, 0.10, and 0.20% (w/v) of cationic hydroxyethylcellulose (HEC) (CTFA designation: Polyquaternium-10, UCARE © Polymer JR 400, Amerchol, Edison, N J) were prepared volumetrically in pH 6.0 - 0.1 buffer prepared from mono- and dibasic sodium phosphate. Standard reagents for the analysis of cationic polymer by the colloid titration method were used. 0-Toluidine blue indicator (Eastman-Kodak, Rochester, NY), 1.00 ml at 4.1 X 10-4 M, was added to approximately 60 ml of 0.001 M sodium phosphate (pH 6.0) buffer. Aliquots of Polyquaternium-10 solution corresponding to 100-400 I-•g of poly- mer were added to the buffer and indicator solution and titrated by a semi-automated