J. Soc. Cosmet. Chem., 25, 655-666 (December 1974) Fluorometric Determination of Formaldehyde-releasing Cosmetic Preservatives E. PATRICIA SHEPPARD, Ph.D., and CLIFTON H. WILSON, Ph.D. • Presented October 9, 1973, Joint Symposium o[ the Association o[ O•cial Analytical Chemists and the Society of Cosmetic Chemists, Washington, D.C. Synopsis-The PRESERVATIVES, 2-nitro-2-brolno-l,3-propanediol, 1-hydroxymethyl- 5,5-dimethylhydantoin, and methane bis[N,N'-(5-ureido-2,4-d'fketotetrahydroilnidazole)- N,N'dilnethylo1] contain HYDROXYMETHYLENE FUNCTIONAL GROUPS which oxi- dize to FORMALDEHYDE under mild conditions of temperature and pH. Formaldehyde released was reacted with 2,4-pentanediove and alnmonia to produce 3,5-diacetyl-l,4- dihydrolutidine which was measured by FLUOROMETRY. Using this technique, the three preservatives were determined in cosinetics with average recoveries ranging from 96 to 106%. Formaldehyde was released quantitatively froin 1-hydroxylnethyl-5,5-dilnethylhydantoin. About 50% of the theoretical yield was obtained froin methane bis[N,N'-(5-ureido-2,4- diketotetrahydroimidazole)-N,N'-dimethylol]. Formaldehyde derived froin 2-nitro-2- brolno-1,3-propanediol was highly dependent on temperature and at 60øC an average value of 2'8% of theoretical was obtained. INTRODUCTION The compounds, 2-nitro-2-bromo-l,3-propaned•ol (Bronopol©),? methane bis [N,N'(5-ureido-2,4-diketotetrahydroimidazole)N,N'-dimethylol] (Ger- mall 115©),* and 1-hydroxymethyl-5,5-dimethylhydantoin (hydroxymethyldi- methylhydantoin)õ (Fig. 1) belong to a class of compounds which Parker (1) has called the "new generation" of cosmetic preservatives. They are incorpo- rated into a wide variety of cosmetic formulations. They contain methylol *Division of Cosinetics Technology, Food and Drug Administration, U.S. Department of Health, Education, and Welfare, Washington, D.C. '{'Bronopol is manufactured by the Boots Company in England and is distributed in the United States by Goldsclnnidt Chemical Co. Gerinall 115 is manufactured by Sutton Laboratories, Roselie, N.J. õAnalabs Inc., North Haven, Conn. 655

656 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS /R H2C•R WHERE H2COH GERMALL H MDM H B RONOPOL Figure 1. Structures o• methylol-containing preservatives (HMDMH refers to hydroxy- methyldimethylhydantoin) Ill • II o o R--C-• •"•-C 2 + • ___.. -• 3H20 NH2 I R 3 Figure 2. Hantzsch reaction producing a fiuorescing derivative from a /5-diketone, an aidehyde, and an amine functional groups and are water-soluble. They do not absorb in the ultraviolet (UV) region of the electromagnetic spectrum and decompose at elevated temperatures. The two latter properties preclude determination of these cos- roetic preservatives by UV spectrophotometry or by gas chromatography. However, the hydroxymethylene groups of these compounds, which theoreti- cally can be oxidized to formaldehyde, and their solubility in aqueous media suggest the possibility of determining them by the fluorometric method for formaldehyde devised by Belman (2). Belman's procedure is based on the earlier work of Nash (3) who, utilizing the Hantzsch reaction, estimated