"j. Soc. Cosmet. them., 28, 259-271 (May 1977) •.. :.• Thin-layer chromatography (TLC) of redox reaction products of oxidative hair dyes i':?• MUKUND J. SHAH Gillette Research Institute, Rockville, MD :,??•:: 20852. 5:'. ?!:?: R•dvd a•g•,, 26, •9Z6. P•,•ntd O•,ob• 1 •, 197•,J•i•, AOAC- :•.:: : • SCC Symposium on Cosmetic Analytical Techniques, Washington, D.C. Synopsis OXIDATIVE or permanent HAIR DYES are based on ALKALINE PEROXIDE OXIDATION of PHENYLENEDIAMINE (PDA) or related AROMATIC AMINES. These amines, when oxidJzed alone or in combination with other phenolic and aromatic amino compounds (couplers), yield a mixture of colored oxidation products. This paper describes the use of thin-layer chromatography (TLC) for the qualitative ' analysis of these complex mixtures of oxidation products. Effects of variables including the nature of ad- sorbency, layer thickness, water content, development of chromatograms, and sample application techniques are presented. Scopes and limitations of chromatography for the isolation and the identification of these dyes are discussed. (?•!:!:: !:: INTRODUCTION Permanent hair dyes, which are presently available commercially, are mostly oxidative •?,i!i•: :i dyes which contain 2 main ingredients. One ingredient is a dye precursor, while the :.•.::: ::i!:!• ??::' ------ other ingredient is a developer or oxidizer, usually hydrogen peroxide. The dyeing process involves mixing the dye precursors with the dye developer in an alkaline me- dium generally around pH 9 to 10. The dye precursors and oxidizer diffuse in the hair fibers where chemical reactions leading to color development take place inside the hair fiber. Dye precursors contain 2 main ingredients: primary intermediates and couplers. Primary intermediates used in oxidative dyes are mainly ortho- and para-aromatic aliamines or aminophenols, which are colorless, but, upon oxidation, give colored oxi- dation products. The most commonly used primary intermediates are p-phenylene- diamine (PDA), p-toluenediamine (TDA), and p-aminophenols (PAP).