September 2020 • Vol. 26 • Issue 7
Survey of Methods Employed to Stabilize Ascorbic Acid in Cosmetic Formulations
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…by Paul Thau
ver 25 years ago, as one of my activities as a technology liaison staff member, I was requested by the marketing group to explore potential methods to stabilize ascorbic acid in a cream or serum vehicle. In that era, this was considered to be a significant challenge because of ascorbic acid’s limited stability in compositions containing water, particularly in the presence of air. After giving the challenge some thought, I contacted a colleague at a major supplier of ascorbic acid. He informed me that his laboratory staff prepared a stable anhydrous composition containing 5% (w/w) ascorbic acid. However, after evaluation of this prototype formulation on my skin, I found the aesthetics to be unacceptable due to the formulation’s unctuous properties. Fortunately, several months later, I came across an article in Cosmetics & Toiletries entitled, “New formulation possibilities offered by silicone copolyols” authored by Gerd H. Dahms, Ph.D. and Alan Zombeck.1 This article stimulated my thoughts that an anhydrous glycol-in-silicone emulsion would be a good vehicle for the formulation of a stable ascorbic acid emulsion, particularly since ascorbic acid is soluble in glycerin, propylene glycol, and other glycols. Our initial trials to prepare such a composition containing 5% (w/w) ascorbic acid were not successful due to emulsion stability issues. However, we subsequently were able to systematically study formulations with different levels of the silicone polyol emulsifier (PEG/PPG-18/18 dimethicone) and found that when the level was raised to a least 6% (w/w), the gel emulsions displayed good stability at a range of storage temperatures. Chemical stability with these prototype formulations were also found to be good. Since our exploratory group had limited resources for refinements to optimize aesthetic properties, this project was transferred to a formulation group overseas. Within the next two years, several commercial products containing ascorbic acid were commercialized. I was not aware of all the details related to these refinements and associated packaging, since I retired from Cosmair/L’Oréal in 1998. Over two decades have passed since that time, and it is my intention in this survey article to review information from recent publications and patents that provide insights on the formulation of cosmetic formulations that have acceptable stability and aesthetic properties. (continued on Page 4)
E X P L O R E T H E W O R L D O F C O L O R W I T H U S • S E P T E M B E R 2 3 rd ...see pages 6-7 for more information.