Analyzing sunscreen emulsions with Raman imaging

With the summer now here, there are many things to look forward to, but by the same token, the battle of getting sunscreen on the kids might not be one of them. What is often overlooked is that sun cream is an extremely advanced emulsion, a prime example of human endeavor against nature, it's a life saver.

Analyzing sunscreen emulsions with Raman imaging

Image Credit: Renishaw plc - Spectroscopy

This article explains how the inVia™ confocal Raman microscope can help us take a deeper look into this powerful and practical cream.

As with pharmaceutical products, the uniformity of material distribution is usually an important quality for creams and emulsions. UV sun creams are made of materials which either absorb (generally organic) or reflect (generally inorganic) the UV light, therefore the stability of particle size and distribution is crucial. It ensures cream coverage is even, and smaller inorganic particles facilitate reflection without totally obscuring the skin to visible light. Sun cream will be stored in varying conditions and temperatures, from the shelves in shops to inside a person’s bag or car. It is absolutely crucial that the uniformity and distribution of the product stays within specification, from leaving the factory up until that hot sunny day - when it is most important for application.

Sun cream held within a stainless steel welled sample kit slide. covered by a glass of cover slip

Sun cream held within a welled stainless steel welled slide and covered by a glass cover slip. Image Credit: Renishaw plc - Spectroscopy

The inVia™ confocal Raman microscope is an amazingly powerful chemical imaging system. It is the optimal tool to help formulate and study creams, whether in water or a different medium from semi-solids to emulsions.

To analyze the sun cream, a small aliquot was covered with a standard glass cover slip.  A high numerical aperture (NA) oil immersion objective was used to evaluate the sample using Raman spectroscopy. This microscope objective offers optimized confocal performance and data collection efficiency, even when sampling down through the cream. Then, the StreamHR Rapide and Empty Modelling™ functions were activated on the inVia, which facilitated data collection for the complete volume within just a few minutes.

The resulting volume image displays singular particles in exceptional detail – their shape, size, composition, and distribution throughout the sample – all acquired in a single scan. In this case it is possible to see that the inorganic TiO2 and organic glycerine form the bulk of the emulsion particles.

The video above demonstrates how changes in the particles occur when moving down through the sample. Due to the specificity of Raman scattered light, other materials could be evaluated in the same way, facilitating even more detail. From data of this quality, formulators and researchers can effortlessly study and improve the creams.

Of course, the creams in production today are exceptionally effective, but improvements can always be made. Toxicity is a specific concern, both for people and the natural environment. Today, there are a number of studies on replicating chemicals that occur within leaves to advance sun creams towards a new sustainable generation. These novel formulations will need to be studied, and Raman imaging is the perfect tool to understand and make sure new sun cream technology is consistent and effective right up to the point of use.

This summer, stay safe – and remember there is good science in the cream.

Acknowledgments

Produced from materials originally authored by Tim Smith, Applications Manager from Renishaw.

About Renishaw

Renishaw is a global company and a recognised leader in Raman spectroscopy. Offering high performance optical spectroscopy products for over 20 years, Renishaw’s Spectroscopy Division is passionate about manufacturing the very best Raman products. It has a team of scientists and engineers specialising in the development, application and production of high performance, configurable Raman spectrometers.

With a foundation built on sound engineering, these systems offer the highest levels of flexibility and performance and are used by academics and industrialists to tackle analytical problems across a broad range of application areas, including life science, chemicals; materials science; pharmaceuticals; semiconductors; forensics; gemmology; antiquities; and green energy, such as photovoltaics.

Renishaw’s Raman systems are easy to use and produce repeatable, reliable data, even from challenging samples. We aim to be a long-term partner, offering quality products that meet customers’ needs, both today and into the future, backed up by expert technical and commercial support.


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Last updated: Aug 3, 2022 at 9:51 AM

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