]. Soc. Cosmet. Chem., 23, 545-548 (August 17, 1972) Determination of Copper-EDTA in Cosmetic Products B. L. KABACOFF, B.S., GEORGE MOHR, and C. M. FAIRCHILD, B.S.* Synopsis--The determination of COPPER-EDTA, the sodium salt of the (ethylenedinitrilo)- tetraacetic acid chelate of Cu(II), which reflects its stability in cosmetic products is described. The analytical method consists of shaking an aqueous dispersion of the cosmetic product with an ION EXCHANGE RESIN, washing the resin free from extraneous matter, and eluting the copper-EDTA from the resin with sodium bisulfate solution. The concentration of copper-EDTA in the eluate is determined by SPECTROPHOTOMETRIC MEASUREMENT of its absorbance at 750 nm. INTRODUCTION Copper-EDTA, the sodium salt of the (ethylenedinitrilo)tetra- acetic acid chelate of copper(II), is a blue coloring matter roughly ap- proximating the color of FD and C Blue No. 1. It has been found to be much more stable to light then the latter dye (1). The affinity for copper(II) of EDTA is quite high, the stability con- stant (pK) being 18.3 (2). Nevertheless, it is conceivable that some com- ponent of a cosmetic formulation may have sufficient affinity for the cupric ion to remove it by exchange from the EDTA anion. Conse- quently, a method of quantitative isolation of the copper-EDTA anion from the product would result in an assay that would reflect its stability. The method of isolation of the anion used in the work reported here is absorption on an anion exchange resin in the chloride form. The cop- per-EDTA anion has a greater affinity for the resin than the chloride ion * Revlon Research Center, Inc., 945 Zerega Ave., Bronx, N.Y. 10473. 545

546 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS and consequently is readily bound by it. The bisulfate ion has a high affinity for the resin and consequently readily elutes the bound copper- EDTA. An efficient method of isolating the copper-EDTA is to pass solutions of it through a column of the ion exchange resin. In practice this was impossible with some products. Lipid materials in some products coated the resin particles, interfering with ion exchange. Extraction with n-butanol to remove the lipids aided the column chromatography. Some products contained water-soluble gels which so increased the viscosity that even on high dilution column chromatography was itnpractical. Interferences by lipids and gels were eliminated by using a batch tech- nique for absorption of the copper-EDTA by the resin. In the final method, an aqueous dispersion of the product was shaken with a large excess of the resin. After absorption of the copper-EDTA, the resin was washed with water to remove extraneous matter and packed into a chro- matographic column. Copper-EDTA was then eluted with sodium bi- sulfate solution and the absorbance of the eluate was determined. Prior extraction with butanol was found to be unnecessary when this method was used. EXPERIMENTAL Reagents and Equipment The reagents used were AG1-X8 ©* anion exchange resin chloride (50- 100 mesh) and a 1% solution of sodium bisulfate, reagent grade. Equip- merit included chromatographic columns of sufficient volume to hold 20 ml of the resin, 10-ml hypodermic syringes, and a microsyringe filter holder (Cat. No. XX$002500)* with prefilter and a GS filter.* The copper-EDTA used in these experiments was the disodium salt containing 4 moles of water of crystallization.* Method An amount of sample equivalent to 30 mg of copper-EDTA was weighed into a 300-ml Erlenmeyer flask. Next, 20 ml of AG1 resin and sufiScient water to make 100 ml were added. The flask was placed on a shaking apparatus and agitated overnight. The sample was then col- lected on a coarse sintered-glass funnel and washed with 200 ml of water. * Cat. No. 1401431, BioRad Laboratories, 220 Maple Ave., Rockville Cen, tre, N.Y. 11570. ? Millipore Corp., Bedford, Mass. 01730. • Geigy Chemical Corp., Ossining, N.Y.