HAIR OILINESS 321 Table II Extraction of Lipids from Hair Samples (batch A) with Dry and with Water-Saturated Solvents Solvents Hair Quantity Quantity of Total of Extract Lipids (mg) (mg) Ether unconditioned 16.5 14.0 Ether/H20 swollen 21.6 14.7 CHC13 unconditioned 15.5 13.2 CHC13/H20 swollen 19.7 13.5 CHCi•:MeOH = 2:1 unconditioned 21.3 14.2 CHC13:MeOH:H20 = 16:8:1 swollen 28.1 14.4 Hair is known to absorb large quantities of water from moist air, most of it rather quickly a gravimetric determination of the water uptake of dried hair in air of 100% RH showed a weight increase of 11% within 20 min and of 15% within 3 h. This absorption is accompanied by a corresponding swelling of the hair fibres. During the process of shampooing the hair is swollen and this might affect the desorbability of lipids from the surface and the accessibility of the sebum underneath the cuticle edges. On the other hand, ether and CHCI3/MeOH are fairly well miscible with water and might act as dehydrating agents which should cause the hair to shrink, thereby possibly occluding or squeezing out part of the sebum e.g., under the cuticle scales. To a certain but lesser extent this should apply to most organic solvents. The following extractions were, therefore, carried out with dry and water-saturated solvents (Table II) and with hair samples which were either conditioned at --•50% RH or at 100% RH (Table III). Table III Extraction of Lipids from Hair Samples (batch B) Before and After Swelling in a Water-Saturated Atmosphere with Dry and with Water-Saturated Solvents Solvents Unconditioned Hair Hair Conditioned in Water-Saturated Atmosphere Quantity Quantity Quantity of Total Quantity of Total of Extract Lipids of Extract Lipids (mg) (rag) (mg) (mg) Ether 14.4 11.7 17.6 12.1 Ether/H20 19.0 12.4 25.3 12.7 CHC13 13.4 11.1 14.0 11.2 CHCl,/H20 17.6 11.4 17.7 11.4 CHC13:MeOH = 2:1 18.1 12.0 19.7 12.3 CHC13:MeOH:H20 = 16:8:1 21.6 12.1 22.3 12.3 In all cases, the composition of extracted lipids was similar, with the presence of water leading to a considerable increase in total weight of extracts. It should be, however, borne in mind that these weight changes are not so much due to lipids as to other water-soluble polar substances as e.g., proteins, phospholipids, urea, detergents, which do not appear in the liquid chromatogram under the elution conditions chosen.

322 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The extraction efficiency of the solvents for lipids increased in the order: CHC13 CHCl,/H20 ether CHC13/MeOH CHCl•/MeOH/H20 ether/water, and in all cases previous swelling of the hair in water vapour leads to a further increase. Water-saturated ether was, therefore, chosen as extraction solvent for all future investigations and hair samples were conditioned for 2 h in a water-saturated atmosphere at room temperature prior to extraction. Optimization of extraction conditions: In a final set of trials the optimum extraction conditions regarding time and temperature were investigated. Preconditioned hair samples were extracted at room temperature and under reflux under conditions given in Table IV. In both cases, Table IV Selection of Extraction Conditions Hair Samples (batch C) Conditioned in Water-Saturated Atmosphere, Extracted with Water-Saturated Ether Extraction Conditions Amount Amount of of Extract Total Lipids (rag) (mg) 1 a) 10 min at room temp. 27.6 ] b) additional 20 min at room temp. 6.4 20.6 c) additional •0 min at room temp. 2.9 2 a) I0 min under reflux 27.6 ] b) additional 10 min under reflux 32.1 20.9 c) additional 40 min under reflux 2.8 roughly the same amounts of lipids with similar composition were extracted after 60 min. This indicates that only the external sebum was affected. At boiling temperature extraction is only faster. As it might be suspected that the small amount of lipids extracted in the last 40 min might already originate from diffusion of internal sebum, we finally decided to use 20 min at boiling temperature as standard conditions for all future extractions (15). ISOLATION OF INTERNAL LIPIDS AND SURFACE BOUND CA- and MG-CARBOXYLATES The existence of "internal lipids" has not yet been generally accepted. However, Curry and Golding have shown (8) that prolonged extraction (75 Soxhlet cycles) with CH2C12, ether, and ethanol does not remove all the lipids present in the hair. It is obvious that lipid substances left in the hair after this procedure bear no relation to the material usually recognized as sebum which is accessible to detergent solutions. Therefore, it may be supposed that it is part of the suspected "internal" lipids. First evidence for the origin of the "internal" lipids was provided by K.D. Bingham (personal communica- tion). He observed that solvent extraction over prolonged periods of time continuously yielded a lipid mixture consisting not only of structural lipids* but also components *I.e., lipids resulting from the keratinization process of hair, consisting mainly of phospholipids, steroIs, mono- and diglycerides and free fatty acids.