Determination of phenolics in cosmetic creams and similar emulsions

A new method for the analysis of phenolics in cosmetic creams has been developed, based on a systematic study of the extractability of five phenolic compounds from such emulsions. A solid-liquid extraction using ultrasound was applied as a prior stage to the chromatographic determination of phenolics in the extracts. Three solvents, hexane, methanol and water, were used as extracting agents. These solvents permit both the de-emulsification of the creams and the extraction of phenolics. A factorial fractional experimental design was developed to analyse the influence in the extraction process of five different extraction variables: ultrasound horn, temperature, extracting volume, cycle and amplitude of ultrasounds. Graphic analysis of results revealed the variables with most influence in the extraction, as well as the interactions between the variables. Finally, the influence of the extraction time and the sample quantity were also studied. With this new method, phenolics can be extracted from silicone-based cosmetic creams in 10 min, using 50 °C as extraction temperature. RSDs (n = 6) calculated ranged from 1.5% for ferulic acid to 6.5% for epicatechin. Recoveries of between 88.9% for gallic acid and 98.4% for caffeic acid were obtained.