J. Cosmet. Sci., 66, 261–270 (July/August 2015) 261 Determination of seven sunscreen agents and two ultraviolet stabilizers in skin care products using ultra-performance liquid chromatography AIMEE GOWELL, JOHN HABEL, CARYN WEISS, and PAUL PARKANZKY, Analytical Sciences, Research & Development, Amway Corporation, Ada, MI 49355. Accepted for publication June 12, 2015. Synopsis Ultraviolet radiation (UVR) is a well-known environmental carcinogen. Protection against UVR exposure has resulted in an increasing number of sunscreen agents being incorporated into a greater variety of cosmetic formulations including moisturizing lotions, color cosmetics, and skin care creams. Meanwhile, global regu- lation of sun care products is changing. New guidelines for sunscreen effi cacy have resulted in a shift in product formulation that requires sunscreen products to provide broad spectrum UV protection. Since not all sunscreen ingredients protect against both UVA and UVB radiation, most sun care products require a com- bination of sunscreen agents. This article describes a new method for simultaneous separation and quantita- tion of seven organic sunscreens and two UV stabilizers using ultra-performance liquid chromatography. This method is capable of resolving all nine analytes, and has been validated for selectivity, precision, and accuracy. Because of the use of core-shell column technology, the separation is also achieved at back pressures compat- ible with conventional high-performance liquid chromatography instrumentation. INTRODUCTION Ultraviolet radiation (UVR) from sunlight is known to be an environmental human car- cinogen. The primary negative effects of UV irradiation of normal human skin are sun- burn, immunosuppression, photoaging, and skin cancer (1). UVR damages collagen fi bers and accelerates the appearance of aging in skin. It also disrupts vitamin A supply (2). UVR is also the main cause of all three types of skin cancer (3,4). Because of these negative effects on human health, sun care products have become very important for the prevention of overexposure to UVR. The use of sun care products is advised for the prevention of sunburn, photoaging, and skin cancer (5). Studies have also shown that daily use of a skin care product with a sun protection factor (SPF) of 16 results in 40% fewer squamous-cell carcinoma lesions of the skin (6). As a result of the proven skin protection of sunscreen products, sunscreen agents Address all correspondence to Paul Parkanzky at paul.parkanzky@amway.com.

JOURNAL OF COSMETIC SCIENCE 262 are being incorporated into a greater number of cosmetic formulations, and the global market for these products has grown to over US$9 billion in 2014 (7). Meanwhile, global regulation of sun care products is changing new guidelines for sun- screen effi cacy are requiring a shift in sun care product formulation (8). Food and Drug Administration (FDA) labelling guidelines require sunscreen products to indicate if they are broad spectrum, meaning that they provide proportional protection against both UVA (320–400 nm) and UVB (290–320 nm) radiation. Since most sunscreen agents do not provide equal protection against both UVA and UVB radiations, most sun care prod- ucts require a combination of sunscreen agents (8). In addition to FDA regulations, other global regions and countries have regulations outlining the use of organic sunscreens (9). For example, the European Union Cosmetic Directive requires sunscreen products to pro- tect against all dangerous UVR and the product labels and claims should provide suffi cient guidance to assist in selecting an appropriate skin care product (10). The global increase in sunscreen use and the regulatory push for products with broad-spectrum UV protection containing multiple sunscreen agents has resulted in the need for a simple, convenient, and rapid method to quantitate multiple sunscreen analytes in a single sun care product. The United States Pharmacopeia and European Pharmacopeia cite monograph methods for quantitating individual sunscreen agents however, the monograph methods are not validated for analyzing sunscreen agents in fi nished sun care products and the methods only quantitate one sunscreen agent at a time (10,11). Methods for analyzing multiple sunscreen agents are available (12–16), but these methods tend to be labor intensive, have lengthy analysis times, poor peak resolution, and only analyze a limited combination of active ingredients. One promising method from an application note was shown to sepa- rate a combination of six organic sunscreens, but upon validation, the method failed to resolve the stereoisomers of homosalate from octisalate (12). Another published method Figure 1. Chemical structures of the seven sunscreen agents and the two UV stabilizers: (A) avobenzone, (B) ensulizole, (C) homosalate, (D) octinoxate, (E) octisalate, (F) octocrylene, (G) oxybenzone, (H) butyloctyl salicylate, and (J) DESM.