JOURNAL OF COSMETIC SCIENCE 28 However, the TOF-SIMS method, by its very nature, is qualitative. It cannot be used to determine the amount of oil that has penetrated into the hair. Therefore, the present work is aimed at developing a method that can provide quantitative data on the penetration of CNO into human hair, using radiolabeled CNO. EXPERIMENTAL MATERIALS CNO was provided by Marico Limited, Mumbai, India. Solvents, such as alcohol, dioxane, and toluene, were of AR grade and were obtained locally. This work was done at Bhabha Atomic Research Centre (BARC) in Mumbai, India. PREPARATION OF RADIOLABELED (3H SUBSTITUTED (TRITIATED)) CNO A known amount of CNO was dissolved in dioxane, and the solution was heated in the presence of tritium gas at 120°C for two hours in the presence of a catalyst (of proprietary composition). Following tritiation, the solvent was evaporated on a Rotovap, and the tritiated CNO (TCNO) was brought to a fi nal volume of 1.5 ml with unlabeled oil. This oil mixture was used in all the studies presented in this communication. HAIR TREATMENT A 10-cm-long strand of Indian hair weighing 100 mg was soaked in 1.5 ml of TCNO. Hair specimens were taken from this sample after one and six hours for further analysis. Surface oil was determined with two single hair fi bers, and penetrated oil was determined on fi ve single hair fi bers taken from the 100-mg sample. Measurements for each treatment time (one and six hours) were made in triplicate sets. The hair specimens were gently blotted on tissue paper soon after their removal from the oil-soaked strand in order to remove the extraneous oil. The approximate weights of two and fi ve hair fi bers were 1.22 mg and 6.1 mg, respectively. RADIOACTIVITY MEASUREMENTS A unique property of tritium is that it is a beta emitter, and therefore, to register its emission it has to be in direct contact with the scintillation fl uid. This means that the TCNO inside the hair is not registered. This enables the measurement of substantive surface oil separately. In a typical measurement two hair fi bers were immersed in 10 ml of the scintillation fl uid and placed into the counter (Hidex, effi ciency 32%). The counts per minute (CPM) were recorded. For the determination of total oil in the hair (surface oil plus penetrated oil), fi ve hair fi bers were solubilized in 400 μ1 of 10% NaOH at approximately 70°C for one hour or until the solubilization of the sample was complete. Five microliters of the hydrolyzed hair solution was added to 10 ml of the scintillation fl uid, and the CPM was recorded after the solution was placed in the scintillation counter (Hidex).

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: