Quantifying Benzophenone-3 and Octyl Methoxycinnamate in Sunscreen Emulsions

In order to minimize the adverse effects of UV radiation, the use of sunscreens in cosmetic preparations has been increasing. Many new cosmetic products containing sunscreens are being developed and are commercially available. Sunscreens are considered drugs in the United States and several other countries, thus the FDA and other regulatory agencies mandate the actives be present at the labeled level by a validated method. Consequently there is a need for development and validation of analytical methods for quantitative determination of sunscreen agents in cosmetic products. High performance liquid chromatography (HPLC) is the most used chromatographic method for qualitative and quantitative determination of sunscreen agents in cosmetic products.

The objective of this study was to develop a rapid, selective and accurate method by reversed-phase HPLC for quantitative simultaneous determination of benzophenone-3 (B-3) and octyl methoxycinnamate (OM) contained in sunscreen emulsions. 

Sunscreens: B-3 presents its maximum UV absorption between 288 and 289 nm and absorbs UVA as well as UVB radiation. The maximum concentration used in solar protector formulations is 6%. It is normally used in a concentration range from 2% to 6% in combination with other chemical filters.7-9 OM presents its maximum UV absorption between 289 and 311 nm and absorbs UVB radiation and to a lesser extent UVA radiation. The maximum concentration used in solar protector formulations is 10%. Normally it is used in a concentration range from 2% to 7.5%.7-9 The chemical structures of these substances are shown in Figure 1.

Materials: All reagents and solvents were of analytical grade or of HPLC grade: methanola; water from a water purification system^b; sunscreens filters^c B-3 and OM.

Sample: The simulated sample used in this research was prepared in the laboratory according to Formula 1.

Apparatus: A liquid chromatographic system^d equipped with a variable UV detector was connected to an electronic integrator^e and manual injection valve fitted with a 20 mL sample loop^f.