Optimized Sunscreen Method Used for Impending 2012 Enforcement of FDA Regulation in Characterizing Their Active Ingredients

On June 14, 2011, the FDA issued stricter regulations on how sunscreen manufacturers can label over-the-counter sunscreen products. In the summer of 2012, manufacturers with an annual sale of $25,000 or more will have to characterize the active ingredients found in their sunscreens (1). As part of the new regulation, sunscreen manufacturers will only be allowed to make the claim that their product reduces the risk of skin cancer and early aging, both of which are primarily caused by UVA rays, if the sunscreen meets the FDA's broad spectrum standard.

While over-the-counter use of sunscreens has been unregulated in the past, the FDA plans to implement stringent regulations for sunscreen manufacturers in characterizing the construct of the active ingredients, as well as the protective properties found in sunscreens. This study provides an easy means of separation for six of the major active ingredients found in many over-the-counter sunscreen products. The method provides baseline resolution between the critical pair octocrylene and octisalate under isocratic conditions, making it an easy to implement method for routine QC analysis.

Experimental Conditions

The optimized method for the sunscreen application was performed on an HP 1100 LC System equipped with a quaternary pump, in-line degasser, variable wavelength detector, and autosampler. The column used for analysis was a Kinetex® 2.6 μm PFP, 100 × 4.6 mm (Phenomenex, Torrance, California). The solvents were HPLC grade and a binary mobile phase of water:acetonitrile (40:60) was used with an isocratic hold of 10 min. The column temperature was 45 °C, and the UV detection was recorded at 313 nm.

Column: Kinetex 2.6 μm PFP

Dimensions: 100 × 4.6 mm

Order No.: 00D-4477-E0

Elution type: Isocratic

Mobile phase: 40:60 water:acetonitrile

Flow rate: 1.5 mL/min

Col. Temp.: 45 °C

Detection: UV–vis @ 313 nm

Inj. Conc.: 0.2 mg/mL

Analytes: 1. Oxybenzone; 2. Octinoxate; 3. Octocrylene; 4. Octisalate; 5. Homosalate; 6. Avobenzone

Results

In the development of this method, C18 phases were tried as the primary column of choice, however coelutions were observed between octocrylene and octisalate. The Kinetex 2.6 μm PFP provided improved resolution and peak shape of all active ingredients. As seen in Figure 1, the often difficult critical pair of octocrylene and octisalate is baseline resolved and has a resolution of 2.32. All of the active ingredients elute within less than 6 min with near symmetrical peak shape.

Figure 1: Sunscreen separation using Kinetex 2.6 μm PFP.

Conclusion

An easy to use LC-UV method has been developed on a Kinetex 2.6 μm PFP for characterizing sunscreen active ingredients. By using only water and acetonitrile, we provide an efficient and cost-saving method to separate critical pairs under isocratic conditions that is easy to implement in a QC laboratory.

References

(1) B. Erickson, "FDA Strengthens Sunscreen Regulations. Chemical & Engineering News (Online)" 2011. http://pubs.acs.org/cen/news/89/i25/8925news5.html (accessed July 18, 2011).

Phenomenex, Inc.

411 Madrid Avenue, Torrance, CA 90501

tel. (310) 212-0555, fax (310) 328-7768

Website: www.phenomenex.com