178 JOURNAL OF COSMETIC SCIENCE BP1.TDC + Ions 1211,m• 2610D10 cts o 41 4O Maas [m/z] BP1.TDC + Ions t2t1..'n 2610010 cts 14000' '• 1 137 ,, ].. II !.!,l..,ILl, i.,,,,, • ,,.,. , 149 140 160 1•0 • l•zl -1 200 220 240 260 280 BPl.'T13• + Ions 121Hm 2610010 cts • • a• • M•neral off Figure 7a. Spectra of positive ions of mineral oil deposited on a silicon wafer, including characteristic positive ions of mineral oil. Characteristic positive ions of mineral-oil-treated hair. The positive spectra obtained from the surface of the cross sections of hair fibers treated with mineral oil are similar to the spectra of the untreated hair (Figure 9). No mineral oil was detected in the treated hair. However, coconut oil and polydimethylsiloxane peaks were observed in the high-mass range, similar to observations made for the untreated hair fiber. This indicates that these hair fibers had been exposed to coconut oil as well as silicones and surfactants. TOF-SIMS IMAGING OF MINERAL OIL IN HAIR BY CHARACTERISTIC POSITIVE IONS The positive ion at mass number 361.26 is unique to mineral oil, and was used to map its distribution in cross sections of untreated and mineral-oil-treated hair fibers (Figure 10a,b). The image of the untreated hair fiber (Figure 10a) shows essentially nothing. For the mineral-oil-treated fiber cross section, there is a slight increase in the number of

PENETRABILITY OF OILS IN HAIR 179 1.5E+6- • 1.0E+6- 5.0E+5 oe 0 BN1.TDC- ions 811Jm 3466808 cts '"'" • lO 15 Uass [m/z] 25 30000: BN1.TDC- Ions 811•n 3466808 cts 25000• • Uass [.Vz] BNI.TDC - Ions 811Jm 3466808 cts 103 , 149 179 ] 116 129 ' 143 193 •[• , • 317 7b. Spectra o• characteristic .•adv• ions o• m•n•ra[ o•] &posk• on a s•]•con w•r. dots, but there is not much activity, suggesting it is quantitatively close to zero. The evidence is quite conclusive that mineral oil does not penetrate hair. This is not quite unexpected, since mineral oil is nonpolar and the cortex of hair is polar and, therefore, has no affinity for mineral oil. COMPARISONS BETWEEN COCONUT AND MINERAL OIL PENETRATION Ion spectra and images clearly identified coconut oil within the hair fiber cross section. The diffusion of coconut oil ranges in depth from partial to complete penetration of the