284 JOURNAL OF COSMETIC SCIENCE (a) (c) (b) (d) CN- (e) Figure 7. a: Backscattered secondary electron image of an N-Merquat©-100-treated hair in cross section embedded in resin. Epicuticle, cortex, and medulla are clearly seen for this hair. b: SIMS image of the CN- (m/z 26D) distribution in the cross section shown in (a). c: SIMS image of the O- (m/z 16D) distribution in the cross section shown in (a). d: SIMS image of the F- (m/z 19D) distribution in the cross section shown in (a). e: SIMS image of the Si + (m/z 28D) distribution in the cross section shown in (a). F- is also predominantly located on the outer surface, which gives evidence that its presence is due to environmental exposure or a cosmetic product. Unfortunately, CI- imaging was not possible due to the composition of the resin. Figure 7e illustrates positive ion imaging, which can be used to detect the presence of metals. The distribution of silicon in Fig 7e is again probably due to a previous silicon-based cosmetic product or surface environmental contamination. Ideally, both

ADSORPTION OF POLYMER ONTO HAIR 285 (a) (b) 60.0, PO 2- ainu = Figure 8. a: Backscattered secondary electron image of a P-Merquat©-100-treated hair in cross section embedded in resin. In this hair sample no medulla is present. b: SIMS image of the PO 2- (m/z 63D) distribution in the cross section in (a). polymer solution and hair should be washed in hexane for siloxane impurity removal before study, although, of course, this is highly impractical for any cosmetic study. Ideally, silicon mapping should be carried out using isotopic labeling. It should be noted that as both the biological matrix of the hair and the polymer have similar elemental compositions it was not possible to obtain any distinction between them. It was for this reason that a phosphorus-labeled polymer was synthesized. P-Merquat©-100 hair. The phosphorus labeling of Merquat©-100 allows for unique de- tection of adsorbed polymer. Figure 8a shows the secondary electron image of a hair. Phosphorus imaging via PO 2- (m/z 63D) is shown in Figure 8b and shows a weak ion count around the epicuticle, indicative of adsorbed polymer. This was not previously detected with the N-Merquat©-100-coated hair. To ensure that it was PO 2- imaged at m/z 63D and not other ion fragments from the hair, a process of ion elimination was carried out. Standard spectra of hydrocarbon, chlorinated, polyethylene glycol, and nylon-6 (synthetic, containing peptide links) polymers contained no negative ion frag- ments at m/z 63D (23). A possible detectable hydrocarbon fragment at m/z 63D is