COCONUT OIL PENETRATION INTO HAIR 29 RESULTS STANDARDIZATION OF THE RADIOACTIVITY OF THE ORIGINAL TCNO Twenty microliters of the 1.5-ml original TCNO sample was diluted with 10 ml of toluene, of which 20 μl was added to 10 ml of scintillation fl uid and placed in the Hidex scintil- lation counter, which gave a CPM of 45,000. Radioactivity is expressed in units of curie (Ci), which refers to decay of 3.7 × 1010 per second (or 2.22 × 1012 per minute) CPM. The radioactivity of the original oil is given by: P Pl P Pl×2.22×10 12 45,000 CPM×10,000 l toluene ×1500 TCNO 20 l×20 CPM Ci ×0.32 efficiency of Hidex which is 2.4 mCi/1.5 ml or 1.6 mCi/ml of TCNO. This number will be used to convert CPM into the volume of TCNO in the hair specimens. MEASUREMENT OF SURFACE OIL In a typical measurement, two hair fi bers were immersed in 10 ml of the scintillating fl uid and placed into the Hidex counter. A CPM value of 106,458 was recorded. From this number we can calculate milligrams of oil in the hair as shown below. Please note that from the defi nition of curie, 1 μCi = 2.22 × 106 CPM: ( ) ( ) ( ) ( ) ( ) ( μ μ μl 6 106,458 CPM ×0.92 sp. gr. oil ×100 2.22×10 CPM Ci ×0.32 eff. of Hidex × 1.6 Ci × 1.22 mg, wt. of hair) The above calculation gives a value of 7.1%. The calculation can be abbreviated as follows: -6 Wt.% surface oil= sample CPM ×80.9×10 wt. of hair MEASUREMENT OF TOTAL OIL In this procedure a known weight of TCNO-treated hair is solubilized in 400 μl of 10% NaOH and a 5-μl sample is used to get the scintillation counts. The total amount of oil can be calculated exactly as above using one additional factor: (400/5) = 80. Therefore, -6 Wt.% total oil= sample CPM ×80.9×10 ×80 wt. of hair For a CPM of 47,100 for one of the samples, the wt.% total oil is 50%. Subtracting the surface oil from the total gives the oil penetrated into the fi ber. The amount of surface oil in the sample taken for the total oil measurement can be calculated by the following formula:

JOURNAL OF COSMETIC SCIENCE 30 Wt.% surface oil× wt. of hair for total oil wt. of hair for surface oil This is given in Table I. Data for surface and penetrated oil are summarized in Table I. Percentages are based on the weight of the treated hair. DISCUSSION OF RESULTS The results in Table I show that the method can determine surface oil. The values for surface oil are slightly on the higher side, which indicates that just dabbing with ab- sorbent paper does not remove all of the surface oil. It probably cannot remove oil re- siding at the scale edges. The bulk oil amounts are unexpectedly high. It is not possible to have such high values for the total oil without the swelling of the fi ber, and CNO does not swell the hair fi ber. The high values obtained for the bulk oil in this study suggest that most of it is indeed surface oil. If we correct for the surface oil in the sample taken for the total oil measurement (column 4 minus column 6), then the results for the pen- etrated oil appear to be more reasonable, especially for the samples treated for one and six hours. CONCLUSIONS The work presented in this communication shows that radiolabeling with tritium can be a suitable method for the quantifi cation of the oil penetrated into hair. The method can distinguish between the surface deposited oil and the oil absorbed into the bulk of the fi ber. This would suggest that the method can be used to quantify other actives that are deposited mainly on the surface of hair. The method can be further refi ned by extracting the hair sample briefl y in a solvent like hexane to remove the surface oil. By doing this prior to analysis, we can confi rm the validity and internal consistency of the surface, total, and penetrated oil results obtained by this method. The researchers plan to do this work in the near future. Table I Distribution of TCNO in Human Hair (wt.% based on hair) Treated with TCNO for One and Six Hours Sample name CPM Total oil CPM Surface oil Wt.% Total oil Wt.% Surface oil Wt.% of surface oil in the total oil test sample Wt.% Penetrated oil 1A 47,100 106,458 50.0 7.1 35.5 14.5 1B 45,300 80,000 48.5 5.4 27.0 21.5 1C 45,200 — 48.4 — — — 6A 61,000 116,000 65.3 7.8 39.0 26.3 6B 62,000 138,000 66.4 9.2 46.0 20.4 6C 62,000 133,000 66.4 8.9 44.5 21.91 All percentages are based on the weight of the treated hair.