SUN CARE
quantities of both emulsifier and dispersant. This balanced approach stabilizes the interface and ensures the efficient dispersion of the powder. Moreover, incorporating cationic emulsifiers has been found to further diminish agglomeration issues in such systems.
Other types of microscopy Thus far, we have focussed on conventional microscopy and the indicators it can reveal in a sunscreen formulation, however, polarised light microscopy can also highly useful in promoting informed decision-making in sunscreen formulation. Polarised light microscopy is a contrast- enhancing technique employed for the visualization of crystalline substances within cosmetic formulations. Whereas unpolarised light emits wavelengths in all dimensions, as seen in Figure 9, polarised light, which is controlled using a polarising filter, limits the transmission of light to a single dimension (or plane).
This technique proves particularly valuable
in discerning features such as crystalline waxes, the phenomena of recrystallization, and instances of inadequate solubilization of solid organic UV filters. Furthermore, it aids in the identification of recrystallized or undissolved preservatives and salts. The specific plane or angle chosen for polarized light visualization is contingent upon the components within the formulation that one seeks to observe, emphasizing the tailored nature of this analytical approach. However, it is essential to recognize that the
presence of crystalline substances does not universally denote formulation inadequacies. Certain elements, such as crystalline waxes or sensory modifiers like cellulose, may manifest as crystals under polarised light without compromising the overall formulation quality. This can be seen in Figure 10, microscopy with and without polarised light of a O/W
20x magnification 20x magnification Figure 8: Microscopy of an O/W emulsion with and without TiO2
emulsion containing cellulose. Understanding the inherent characteristics of the chassis being evaluated is crucial in interpreting microscopy images effectively and distinguishing between normal crystalline elements and those that signify formulation challenges. Optical microscopy offers detailed insights
into the shapes, sizes of emulsion droplets, and the crystalline structures within them. It provides some information about the emulsion’s microstructure and morphology, although within certain limitations. For a more comprehensive analysis of morphology, Cryo- SEM (Cryogenic Scanning Electron Microscopy)
in the oil phase
is highly recommended. This interdisciplinary tool allows for the
observation of dispersed water phase droplet size distribution, morphology, and interphase interactions. When combined with Energy- dispersive X-ray spectroscopy (EDS), Cryo- SEM enhances the understanding of element distribution, providing a deeper comprehension of the microstructure in sun care formulations. Comparative analysis using both non- polarised and polarised light, and cryo-SEM, becomes a beneficial practice, offering a comprehensive understanding of the subtle nuances within the formulation microstructure.
O/W Emulsion with TiO2 agglomeration O/W Emulsion with ZnO agglomeration
35
20x magnification Figure 7: Examples of agglomerated TiO2 O/W Emulsion and ZnO O/W Emulsion with TiO2 in oil phase
20x magnification
ProductVision software is the global choice to solve the problems of managing formulation and new product development allowing you to keep ahead of the game
Functionality Modular design Powerful query function Graphical interface Automates development Reduces time to market Integrates into ERP systems Powerful legislative tools GHS compliant Full security and auditing Web accessible features
Personal care solutions Guidelines & Restrictions checks to ensure product compliance Track testing & QC requirements Allergens calculation and reporting IFRA dosage compliance for fragrances Built-in reporting tools Automatic complex calculations Product properties
• Costs • Allergen content • Product restrictions and many more …
For more information email us at
sales@asdsoftware.com
www.asdsoftware.com
www.personalcaremagazine.com February 2024 PERSONAL CARE
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