INTRODUCTION TO TESTING COSMETICS CON- TAINING RADIOISOTOPES* By Lores C. BAP. AIL, M.D.$ and JosEPH J. PESOATOP. E** United States .Testing Co., Inc., Hoboken, N. )e. WE ARE PRESENTING today a preliminary study on the use of radioisotopes in the cosmetic in- industry. Radioisotopes have al- ready been used in the study of skin penetration by various types of chemicals and very recently it was demonstrated by means of radioisotopes that iodine does pene- trate several layers of the skin. The penetration of tincture of iodine into human tissues was established by Barail as early as in 1922 when he applied iodine by electronosmosis. The penetration of mercury derivatives and of hor- mones has been studied in the past and as far as we know no one has ever used radioisotopes in their studies on the skin. That is why we decided to devote our first experiments to simple, metal-free cosmetics, and to continue this in- vestigation by testing more and more complicated preparations as time goes on. * Presented at the Dec. 8, 1949, Meeting, New York City. ++ Present address 222 W. 83rd St., New York, N.Y. ** Present address Foster D. Snell Inc., New York, N. Y 277 As you all probably know, radio- isotopes are elements that have been activated with atomic en- ergy to a higher energy level. These elements tend to return to their normal state and in doing so will continuously emit radiation over a period of time. This period of time can be anywhere from seconds to millions of years. In the case of Carbon 14, which was used in this investigation, it has a half life of over 5000 years. In other words the activity of Carbon 14 would reduce itself to half in approximately 5000 years. When- ever conducting experiments using isotopic procedures, we confine our- selves to a radioisotopic element which is a normal constituent of the substance in question. This justifies our selection of Carbon 14. The radioisotope of Carbon 14 behaves chemically as a normal carbon atom of atomic weight 12, with only one physical exception: it emits soft beta-radiation. This type of radiation is quite difficult to measure, since it is easily stopped and absorbed by a small amount of material, such as a sheet

278 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ß of paper. For this reason, it was imperative that we use an extremely thin end window G. M. tube. This window, undoubtedly, would absorb some of the radiation, but the more energetic particles would go through and be recorded on our amplifying system. At the conclusion of the experim•ent where we had sections of skin tissue to measure for radiation, we used the Q-gas counter. This type of in- strument is especially adapted to measuring Carbon 14 radiation. The sample is placed directly in the tube, so as to eliminate any ab- sorbing material. If any radiation was emitted from the skin surface, it most certainly would be detected by the Q-gas counter. C•,H3•Br + Mg --• C•H3•MgBr * * C•H•MgBr q- CO2 -• C•Ha•COOMgBr , C•C•MgBr + HCI • , C•,Ho•C•H + MgCIBr , C•C•Ag + C•CH•I • , C•,Ho•C•C•Hao + Agl Cetyl Palmkate The radioactive carbon dioxide is generated from the barium car- bonate purchased from the Atomic Energy Commission, by the addi- tion of sulfuric acid. The complete synthesis was made in a closed system under nitrogen gas atomizer making use also of liquid nitrogen to freeze the Grignard reagent and the carbon dioxide gas. SYNTHESIS OF CETYL PALMITATE WITH RADIOACTIVE CARBON 14 We purchase all our isotopes from the Atomic Energy Commis- sion, Oak Ridge, Tenn. Isotopic Carbon 14 comes in the form of barium carbonate. The bottleneck in conducting an investigation with isotopic tinctures is found in the synthesizing of the tagged com- pound. In making these compounds, we are working with small quan- tities of material and special precautions should be taken. Our radiochemists wear surgical type gloves and a special respirator when working with radioactive car- bon dioxide gas. The following is a general outline on the syn- thesis of the labeled compound used: PREPARATION or THE CREAM We labeled modified USP cold cream with synthetic cetyl palmi- rate, containing Carbon 14. The composition of the modified USP cold cream was as follows, as based on 1000 grams: Spermaceti wax, gm ................. 125 Beeswax, gm ....................... 125 Sodium borate, gm .................. 5 Rose water, gm ..................... 245 Distilled water, gm ................. 250 Mineral oil (replacing Almond oil), gm. 250 APPLICATION OF THE CREAM AND COUNTS in Fivo The tests to determine the degree of penetration of the labeled sper- maceti were made on animals. There was an important discussion * Denotes the radioactive Carbon 14, which was incorporated in the compound.