LC-MS/MS shines light on sunscreen UV filters

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  • Published: Mar 1, 2017
  • Author: Ryan De Vooght-Johnson
  • Channels: HPLC
thumbnail image: LC-MS/MS shines light on sunscreen UV filters

Analysis of UV filters presents challenges

UV filters are the active chemical ingredients in sunscreens, protecting the user from harmful UV radiation. They are also found in many other cosmetics, such as lipsticks, moisturising creams and some hair products. Many countries have legislation detailing the permitted levels of filters in consumer products, although products containing unapproved chemicals can sometimes be a problem, needing investigation by consumer protection authorities.

Although UV filters undoubtedly save lives by reducing the likelihood of skin cancer, there has been concern about their possible harmful effects on the skin. The UV filter PABA (p-aminobenzoic acid) has been banned in the EU, owing to concerns that it may promote damage to skin cells by UV light. There has also been concern about the adverse environmental effects of some filters. Benzophenone-3 (oxybenzone or 2-hydroxy-4-methoxybenzophenone), a commonly used filter, has been shown to cause damage to coral in areas popular with tourists.

The analysis of UV filters is challenging: firstly because of the diverse matrices in which they are found, and secondly because of their varied chemical structures. Although many methods, including LC/MS and GC/MS, have been used, improvements are still needed. The Chinese scientists aimed to find simple procedures that would successfully extract filters from a variety of consumer products, and then separate and detect the different filters.

UV filters extracted from consumer products and detected by LC-MS/MS

The researchers looked at 15 diverse UV filters widely found in consumer products. They contained various functional groups, such as ketone, phenolic OH, ester, ether, sulfonic acid and amine, giving them different chromatographic properties.

The researchers examined a range of different consumer products. Initially they attempted a simple aqueous methanol extraction, but struggled with waxy materials such as lipsticks. Eventually they found a successful method involving first homogenising the sample with a little tetrahydrofuran containing 0.2% ammonium hydroxide solution, then extracting with 80% aqueous methanol with sonication. The ammonium hydroxide was required to give good extraction of the acidic filter UV-T (2-phenyl-1H-benzimidazole-5-sulfonic acid).

The 15 UV filters were then separated and identified by LC-MS/MS (HPLC and tandem mass spectrometry) using an ESI (electrospray) source. Positive ion mode was used for 12 of the filters, but three of them required negative ion mode. Slightly different HPLC gradient eluting solvents were used for the two different ESI modes: methanol with 0.1% aqueous formic acid for the positive ion mode compounds, and methanol with 0.1% aqueous ammonium hydroxide for the negative ion mode compounds. Both runs used the same column, a Waters XBridge C18, which proved to be the best out of several columns tested. The mass spectrometer was a Waters Xevo TQ MS triple quadrupole instrument. Characteristic molecular ions and breakdown ions were identified for each compound.

The method showed good separation, linearity, sensitivity and stability. The limits of detection (LOD) ranged from 2 to 20 mg/kg, while the limits of quantification (LOQ) ranged from 5 to 50 mg/kg.

Improved method for detecting UV filters in consumer products devised

The new method allows the accurate detection of a wide range of commercial UV filters in a variety of different consumer products. The use of aqueous methanol minimises solvent costs. The only drawback is the need for double runs, one for the positive ion mode with aqueous formic acid, and one for the negative ion mode with aqueous ammonium hydroxide. Possibly future work will lead to the development of a single-run method.

Related Links

International Journal of Cosmetic Science, 2017, Early View paper. Meng et al. Simultaneous separation and determination of 15 organic UV filters in sunscreen cosmetics by HPLC–ESI-MS/MS.

Archives of Environmental Contamination and Toxicology, 2016, 70, 265-288. Downs et al. Toxicopathological effects of the sunscreen UV filter, oxybenzone (benzophenone-3), on coral planulae and cultured primary cells and its environmental contamination in Hawaii and the U.S. Virgin Islands.

Wikipedia, Sunscreen

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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