Direct Analysis of Dimethicone in Aqueous Emulsions by Infrared Spectroscopy.

Dimethicone is a mixture of fully methylated linear siloxane polymers of various molecular weights. This water-insoluble ingredient provides exceptional skin protection and lubrication when incorporated into skin and hair care products. Quantitative analysis of dimethicone is often required to support quality assurance testing of finished products. We report a new, rapid analytical method based on Fourier transform infrared spectrometry, using a special attenuated total reflectance cell to determine concentrations of dimethicone directly in aqueous emulsions present in personal care products. This rapid, simplified method eliminates sample preparation to remove water, while providing reliable results across a wide range of dimethicone concentrations.