42 JOURNAL OF COSMETIC SCIENCE a screening tool to identify vehicles that interact with sebum and can possibly be used for follicular drug delivery. ACKNOWLEDGMENTS This study was supported by SmithKline Beecham Consumer Healthcare, Parsip- pany, NJ. REFERENCES (10) (11) (12) (13) (14) (15) (1) A.C. Lauer, L.M. Lieb, C. Ramachandran, G.L. Flynn, and N.D. Weiner, Transfollicular drug delivery, Pharmaceut. Res. 12, 179-186 (1995). (2) B. Illel, Formulation for transfollicular drug administration: Some recent advances, Crit. Rev. Therapeut. Drug Cam Sys., 14, 207-219 (1997). (3) G.V. Gupchup and J. L. Zatz, Targeted delivery to pilosebaceous structure, Cosmet. Toilerr., 112, 79-87 (1997). (4) J. S. Strauss, P. E. Pochi, and D. T. Downing, The sebaceous glands: Twenty five years of progress,J. Invest. Dermatol. 67, 90-97 (1976). (5) K.M. Nordstrom, J. N. Labows, K.J. McGinley, and J.J. Leyden, Characterization of wax esters, triglycerides, and free fatty acids of follicular casts,J. Invest. Dermatol. 86, 700-705 (1986). (6) M. R. Motwani, L.D. Rhein, and J. L. Zatz, Differential scanning calorimetry studies of sebum models, J. Cosmet. Sci., 52,211-224 (2001). (7) S. R. Gorukanti, L. Li, and K. H. Kim, Transdermal delivery of antiparkinsonian agent, benztropine. I. Effect of vehicles on skin permeation, Int. J. Pharmaceut. 192, 159-172 (1999). (8) H. Tanojo, E. Boelsma, H. E. Junginger, M. Ponec, and H. E. Bodde, In vivo human skin permeability enhancement by oleic acid: A laser Doppler velocimetry study,J. Controll. Release, 58, 97-104 (1999). (9) P. Mura, M. T. Faucci, G. Brainanti, and P. Corti, Evaluation of transcutol as a clonazepam trans- dermal permeation enhancer from hydrophilic gel formulations, Eur. J. Pharmaceut. Sci., 9, 365-372 (2000). E. Squillante, T. Needham, A. Maniar, S. Kislalioglu, and Z. Hossein, Codiffusion of propylene glycol and dimethyl isosorbide in hairless mouse skin, Eur. J. Pharmaceut. Biopharmaceut., 46, 265-271 (1998). H. L. Hood, M. E. Kraeling, M. G. Robl, and R. L. Bronaugh, The effects of an alpha hydroxy acid (glycolic acid) on hairless guinea pig skin permeability, Food Chem. ToxicoL, 37, 1105-1111 (1999). J. C. Shyamla, Follicular delivery of erythromycin from nonionic liposomes and emulsions, Doctoral dissertation (1997). D. W. Osborne and D. A. Hatzenbuhler, "Influence of Skin Surface Lipids on Topical Formulations," in Topical Drug Delivery Formulations, D. W. Osborne and A. H. Amann, Eds. (Marcel Dekker, New York, 1990), pp. 69-86. S. C. Jayaraman, C. Ramachandran, and N. D. Weiner, Topical delivery of erythromycin from various formulations: An in vivo hairless mouse study, J. Pharmaceut. Sci., 85, 1082-1084 (1996). N. Waranuch, C. Ramachandran, and N. D. Weiner, Controlled topical delivery of hydrocortisone and mannitol via select pathways. J. Liposome Res., 9, 139-153 (1999).

j. Cosmet. Sci., 53, 43-58 (January/February 2002) Validation of an analytical procedure for the determination of oxidative hair dyes in cosmetic formulations URSULA VINCENT, GUY BORDIN, and ADELA R. RODRIGUEZ, European Commission, Joint Research Centre, Institute for Red•rence Materials and Measurements, Retieseweg, B-2240 Geel, Belgium. Accepted for publication November 15, 2001. Synopsis A high range and variety of cosmetic formulations that contain oxidative hair dyes and matrix-forming compounds have been industrially developed over recent years and are now available on the international market. Member states of the European Union are responsible for conducting analyses of cosmetic products as deemed necessary by law and European regulation enforcement. Therefore, inspection authorities as well as the cosmetics trade and industry need validated analytical methods for the identification, characterization, and/or quality control of specific active ingredients or formulations with the aim of implementing the European Union Cosmetic Directives (76/768/ECC, 95/17/EC). In this frame, we validated a candidate reference method that enables the identification and quantification of hair dye-forming compounds. This method consists of a separation by RP-HPLC coupled with a DAD after a liquid-liquid extraction procedure for separating matrix components from the dye-forming compounds. The validation of the method includes common criteria such as the repeatability of the analysis and the establishment of figures of merit, as well as statistical evaluations and quality assurance in order to follow the recommendations of the Eurachem guide for analytical measurements. INTRODUCTION A cosmetic formulation for permanent hair dyeing can be described as a mixture of two kinds of products: oxidative hair dyes, the so-called active compounds, and matrix compounds in which the dyes are embedded. Oxidative hair dyes are aromatic organic compounds, e.g., amines, phenols, and derivatives, while a broad range of products can be used as matrix compounds. These products play different roles in hair formulations. For example, they act as surfactants, pH adjusters, consistency providers, antioxidants, emulsifiers, film formers, preservatives, or perfumes. The biggest analytical challenge is thus to identify and quantify the active products into a complex matrix mixture in order to propose a reference method for the analysis of this type of cosmetic product with the aim of implementing the European Union Cosmetic Directives 76/768/ECC and 95/ 17/EC (1). 43