USES OF CHELATING AND SEQUESTERING AGENTS IN COSMETICS* By G. H. GOODYEAR and B. L. HATHORNE Glyco Products Company, ]nc., Brooklyn 2, N.Y. LET US TALK ABOUT chelating and sequestering agents and their properties. These materials should enable the cosmetic manufacturer not only to preserve and insure superior properties of his products but should be tools to give him improved products. Soluble metallic ions cause trouble in manufacture, shelf life, and application of cosmetic prod- ucts. The manufacturing problems are more readily avoided but shelf life and application problems can be very serious. Actually, it is diffi- cult to obtain raw materials which are consistently or ever completely free from trace mineral contamination. Even though the specifications show them to be very low, there are usually contaminants present and they can frequently cause trouble. They come in chemical raw materials, they are removed from the sides of mixing vessels, they are in the water used, and come from the surface of the bottles or containers in which prod- ucts may be stored. And, speaking of containers, it has been aptly said that a cosmetic product must be designed for the container in which it is to be sold. Bottles and other containers just don't have completely inert surfaces. Glass will yield a little sodium hydroxide and calcium ions on standing. And the very popular colored glass may yield other ions which are there to color the glass. This may seem a little far fetched but let me point to the fact that one of the new ideas in agriculture, which is working quite satisfactorily, is the process whereby they place trace elements in a glass frit, which is then spread over the soil so as to release these trace elements slowly as they are needed by the growing plants. Also, beautiful and artistic bottles have an unusually large amount of sur- face in relation to their contents. Obviously, this gives an even greater chance for solution from those walls. Some of you may comment that many in the industry are using plastic bottles and so have none of these troubles. These plastic bottles are made from metal dies and these metal dies do wear. After they are worn, they are plated back to original dimen- sions and sometimes this plating is done with chromium. If one were * Presented at the January 12, 1954, Meeting, Chicago Section Chicago, Ill.

CHELATING AND SEQUESTERING AGENTS IN COSMETICS 97 to analyze a complete bottle, the amount of metal therein would seem insignificant. Nevertheless, what is there, is on the surface of the bottle, where it can most readily get into the product and its effect may be many times greater than would appear from the analytical figures. Actually, the question in my mind is: How many milligrams of active perfume are present in a 1-oz. jar of cold cream and what proportion of that small amount of perfume can be catalytically oxidized before an undesirable or off odor is noticeable? The most obvious method of preventing trouble from metallic ion contamination is to see that all of them are removed or that only raw materials are bought which have none of them present. This is impossible. The most satisfactory answer at present is to inacti- vate residual metallic ions insitu during the course of manufacture. This can be done by sequestering and chelating agents. There are numerous examples of sequestering and chelating agents in nature. For instance, chlorophyll has a complex, organic structure with which magnesium is chelated. Many synthetic organic chemicals have chelating power. Thus 8-hydroxyquinoline will chelate copper to form a 8-quinolinolate which is widely used in the textile industry as a mildew- proofing agent. There are numerous other organic products offered for special uses. Anyone interested in others having chelating properties can find many examples in the book "Chemistry of the Metal Chelating Compounds" by Martell and Calvin. There are two types of commer- cially available materials for the purpose of inactivating metallic ions. The first of these, probably more familiar because they have been generally available for a longer period of time, are the complex phosphates. These have many desirable properties but they have other characteristics which limit their applications in the cosmetic field. The organic chelating agents of the ethylenediamine tetraacetic acid (EDTA) type and its salts are among the most effective of all the chelating agents, and at the same time they can be marketed at a price low enough to be economically useful. I shall compare the properties of the EDTA type of compounds with that of the complex phosphates a little later so that the field of usefulness cov- ered by each of them will be understood. The structure of ethylene diamine tetraacetic acid is as follows: HOOCCH2--N CH2C--O CH2 OH I CH2 OH I HOOCCHg--N--CH2C=O Note that it resembles a lobster's claw ready to grab any calcium ion which may be present. The word "chelate" comes from the Greek word "kelos" which refers to the great claw of the lobster. Chelating (Kelating) is