DETECTION OF CATIONICS ON KERATIN 275 wool swatches treated with all these dyes, however, wool swatches are preferable for staining studies because of their sheet-like physical form and because they provide a whiter background. Figure ! summarizes the results from staining wool swatches after treatment with the alkyl trimethyl ammonium bromides. This plot shows that Red 80 is most similar to Rubine. Visual observation of the swatches is even more revealing (Figure 2). For these three urea derived dyes, little staining occurs on the controls or the swatches previously treated with the n-butyl to n-octyl quaternaries however the n-decyl quaternary treated swatch produces moderate staining, and the higher chain length quaternaries produce more intense staining, with a decrease in intensity at n-octadecyl probably because of its low water solubility, and therefore lower sorption. On albino human hair, staining by the n-decyl quaternary is not as clear as on wool swatches, probably because of the yellow background. However, staining by n- dodecyl and higher chain length quaternaries is readily apparent. Both hair and wool swatches treated with cationic polymers, e.g. quaternium-19 or poly-ethyleneimine stain with Red 80 as with Rubine. The control swatches and n-butyl to n-octyl quaternary treated swatches stain even less with Red 80 than with the other dyes (Figure 1). Light to no staining for the n-butyl to uJ z BO 70 60 40 30 20 I0 RUBINE o RED 80 RED 84 ORANGE II m ORANGE G C4 C6 Ce Cio Ci Ci4 Ci6 QUATERNARY CHAIN LENGTH Figure 1. Reflectance values vs. quaternary chain length. Ci8

276 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS