358 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS tive. The conditioning performance of the dodecyl derivative was found to be much improved if the hair was kept damp at 56øC for several hours, with less improvement after storage at room temperature and even less improvement after storage in a refrig- erator (3). Finkelstein and Laden concluded that some structural rearrangement of the cationic surfactant was taking place at the fiber surface. The experiments of Finkelstein and Laden were carried out on hair that had been extracted twice with Triton X-100 and once at room temperature with a solution made up of 60% acetone and 40% of 1% aqueous sodium chloride, procedures claimed (3) to remove sorbed anionics from hair. An experiment was conducted on six samples of human hair collected from a hairdresser so as to test the effectiveness of these extraction methods. Samples of untreated hair, and of hair previously extracted by each of the above proce- dures, were extracted for 60 minutes at 60øC with isopropanol/pH 7 buffer. This procedure has previously been shown to be very effective for extracting anionic surfac- tants from wool (9) and is assumed to be equally effective in removing cationic surfac- tants. The assay procedure for anionic and cationic contents is shown in the Experi- mental section. Results are shown in Table I. It is apparent that neither of the proce- dures is effective in removing anionic or cationic surfactants from hair. The wide range of contents of both anionic and cationic surfactant for the various hair samples illustrates the importance of a satisfactory preparation procedure before the hair is used for sham- pooing/conditioning experiments. The anionic surfactant content of these hair samples varied from 1 to 8 •moles/g (0.03% to 0.25% SDS equivalents) and the cationic surfactant content from 0 to 3 •moles/g. The important conclusions of Finkelstein and Laden (3), that desorption of cationic Table I Anionic and Cationic Surfactant Contents (p•mole/g) of Various Samples of Human Hair as Collected From a Hairdresser and After Treatment With Triton X-100 a or Acetone/Salt b Solutions No Triton X- 100 Acetone/aqueous Sample treatment washed a NaC1 washed b Anionic surfactant 1 2.4 2.9 2.9 2 3.4 2.4 3.O 3 8.3 7.9 7.1 4 1.! 2.4 1.9 5 0.8 0.9 0.5 6 6.3 6.7 5.2 Mean 3.7 3.9 3.4 Cationic surfactant 1 1.4 1.7 1.6 2 1.6 1.5 1.2 3 0 0.4 0.3 4 0.9 1.4 1.0 5 0 0 0 6 2.O 3.7 2.8 Mean 1.0 1.4 1.1 Hair shampooed twice with Triton X-100 for 30 sec and rinsed thoroughly with water at 40øC. Hair extracted with a solution made up of 60% acetone, 40% of 1% sodium chloride in water for 60 min at 25øC.

CATIONIC-ANIONIC INTERACTIONS 3 5 9 surfactant and structural rearrangement occur during conditioning of human hair, might therefore depend on interaction of the cationic surfactant with nonextracted anionic surfactant. Such anionic-cationic complexes would behave in a manner similar to oils, and the re-oiling of hair after shampooing and conditioning might be effected through such a mechanism. Should this mechanism for conditioning be substantiated by further testing on human hair, then it will be evident that the level of anionic surfactant on hair as a result of shampooing treatments is a major factor in determining conditioning behavior. The importance of length of alkyl chain and pH of both shampoo and conditioners might also be sorted out scientifically on the basis of such a mechanism. ACKNOWLEDGMENT The competent technical assistance of Ms. J. A. Saunders is gratefully acknowledged. REFERENCES (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) C. R. Robbins, in Chemical and Physical Behaviour of Human Hair, 2nd ed. (Springer-Verlag, New York, 1988), Chapter 5. G. V. Scott and C. R. Robbins, Effects of surfactant solutions on hair fiber friction, J. Soc. Cosmet. Chem., 31, 179-200 (1980). P. Finkelstein and K. Laden, The mechanism of conditioning hair with alkyl quaternary ammonium compounds, Appl. Polym. Symp., 18, 673-680 (1971). C. R. Robbins, G. V. Scott, and J. D. Barnhurst, The influence of presorbed anionic surfactant on the sorption of cationic surfactant by hair, Textile Res. J., 38, 1197-1199 (1968). R. G. Aickin, The adsorption of sodium alkyl sulphates by wool and other fibres,J. Soc. Dyers Colour., 60, 60-65 (1944). J. A. Maclaren and J. A. McDermott, Some effects of the sorption of cationic surfactants by wool, J. Text. Inst., 75, 416-423 (1984). L. A. Holt and I. W. Stapleton, The distribution of some fluorescent anionic surfactants applied to wool, J. Soc. Dyers Colour., 104, 387-392 (1988). L. A. Holt and I. W. Stapleton, The distribution of anionic and cationic surfactants on wool, Proc. Textile Inst. World Conf., Sydney 1988, pp. 420-427. L. A. Holt and J. Onorato, The substantivity of various anionic surfactants applied to wool, Textile Res. J., 59, 653-657 (1989). L. E. Aicolina, I. H. Leaver, and I. W. Stapleton, Fluorescence quenching studies of the self- association in water of fluorescent surfactants. Alkaryl-2-pyrazolines and alkyl-7-hydroxycoumarins, Dyes and Pigments, 11, 213-232 (1989). E. Heinerth, in Anionic Surfactants-Chemical Analysis, John Cross, Ed. (Marcel Dekker, New York, 1977), p. 221. G. V. Scott, C. R. Robbins, and J. D. Barnhurst, Sorption of quaternary ammonium surfactants by human hair, J. Soc. Cosmet. Chem., 20, 135-152 (1969).