USE OF RADIOISOTOPES IN DETERGENT AND COSMETIC RESEARCH By M. F. NELSON* Presented March g, !959, New York Chapter APPLICATIONS OF radioisotopes to the problems of industry have been increasing at a tremendous rate during the past fifteen years. The Atomic Energy Commission estimates that industry is now saving nearly one billion dollars a year from the use of radioisotopes and predictions are that a saving of tens of billions of dollars within a decade will be realized (1). Probably one of the most fertile fields for the use of radioisotopes is in the detergent and cosmetic industry. Use of beta and gamma gauging in production control has been undertaken, and use of radiation itself as a method of sterilization of products or product ingredients normally altered by bacteria is soon to be realized. Radiotracer techniques have found and are finding considerable usage as aids to product development and improve- ment. However, only a limited usage of radioisotopes has already been undertaken in comparison with the full potentiality of these materials as research or production tools, and corresponding industrial savings. The restricting factor in many instances has been a lack of knowledge of the uses of radioisotopes and also a lack of personnel trained in their usage. Radiotracer techniques have already been used in a variety of ways in detergent and cosmetic research. Unfortunately the literature gives only a portion of the techniques which have been used to aid in the resolution of specific problems. This is due in part to the specificity of the particular study conducted or an unwillingness on the part of some industrial manage- ment to reveal techniques that may be direct aids to competitors in product improvement. Also some experiments which have been undertaken and techniques, which have been developed are faulty or are not suitable for publication. Faulty procedures often occur due to a lack of knowledge of radiotracer technique, as well as a tendency to formulate the method used to satisfy or substantiate advertising claims. Therefore, factors are often overlooked or ignored in tracer experiments that should be considered such as decrease in activity due to self or media adsorption of weak beta parti- cles, failure to maintain constant geometry in a series of radioassays, * Radiotracer Laboratory, Atlas Powder Company, Wilmington 99, Del. 320

RADIOISOTOPES IN DETERGENT AND COSMETIC RESEARCH 3:21 apparent decrease in concentration of a tagged material due to penetration into an adsorbing substrate, decrease in radioactivity due to hygroscopicity of a tagged material or substrate to be evaluated, failure to correct for the decay of short half-life nuclides, metabolic decomposition of the tracer compound by animal bodies, and improper use of instrumentation. To illustrate with an actual experiment: Several years ago a group of experimenters wished to evaluate the ability of various types of formulations in removing dirt from living skin. Amor- phous carbon 14 mixed with soot to represent soil, was rubbed into an area of animal skin and radioassays were taken. The "skin cleaners" were applied, wiped off the skin and another radioassay was taken. Initially it was found that results were very erratic and further investigation showed that in the assays, the Geiger tube was not being maintained a fixed distance from the skin--"The geometry of the system was not constant." At the "conclusion" of the experiment it was noted that one formulation showed high eflSciency in removal of dirt as was shown by a marked decrease in radioactivity, although visually the skin area treated did not appear as "clean" as it did when treated with other cleansing agents. Subsequent investigation showed the formulation to cause a very marked decrease in radioactivity directly after it had been applied and even before the skin was wiped free of the cleanser and the dirt removed by the formulation. It was found that the formulation contained high concentrations of oils (in contrast to the other formulations tested) which spread over the skin